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#1351
Webberweather53

Posted 03 July 2018 - 09:44 AM

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As noted earlier this year and 2012 are on virtually equal footing w/ subsurface temperature anomalies in the Equatorial Pacific but couldn't be farther apart in the subtropical Northeast-central Pacific, tropical Atlantic, and how the El Nino events initially evolved. 2012-13 faded all the way deep into cold neutral conditions by the winter but will this year follow suit? The literature and observations noted above argue otherwise that this won't be a head fake.

 

2012

IDYOC002.201207.gif

 

 

IDYOC002.201807.gif

 

 

If you still don't buy into what I'm saying above w/ the PMM & tropical Atlantic influencing ENSO that's fine, we'll have the luxury of watching this idealized experiment take place w/ the same subsurface look being initialized in the Eq Pacific but vastly different boundary conditions in the subtropical North Pacific and tropical Atlantic, all without having to use a climate model!


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#1352
Phil

Posted 03 July 2018 - 10:04 AM

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If you compare the subsurface temperature anomalies to years like 2012, last year, 2014 wherein a significant NINO (or in the case of 2014 strong NINO) head fake occurred, we're blowing them out of the water (no pun intended :) ) with exception to 2012.

2012 is an interesting case study because neither a +PMM or cold Atlantic were present during the summer of 2012, and furthermore most of the intense +SSTAs were confined to the far EP unlike this year. The warm tropical Atlantic, -PMM, and where the greatest warming initiated in the Eq Pacific were tip offs of a NINO head fake in 2012. I use 2012 as a prime example w/ similar subsurface warming and a bgd climate to this year to showcase how the PMM and tropical Atlantic as I discussed above are important in determining ENSO evolution. I believe based on observations & literature (some of which I linked above) that they provide valid, easy to recognize clues wrt forthcoming ENSO behavior and are reliable warning signs of either impending El Ninos or head fakes, 2012 just solidifies this rationale.

This year however couldn't be more different atm from 2012 outside of the subsurface and is following the recipe of success w/ a cold Atlantic, +PMM, and initiating in the Central Pacific, I'll explain why the latter is important below.

anomnight.7.2.2012.gif

If you also were to analyze the early evolution of all these head fakes, they all observed vigorous eastern Pacific warming early on in their lifetimes, whereas this year seems to be following a completely different path with the most intense +SSTAs based in the central Pacific. We know that the climatological SSTs near the dateline are closer to the threshold necessary to readily generate convection. The implications of this are that weak events based in the CP like this year instead of the EP (as was the case initially in 2012, 2014, & 2017) are more likely to generate convective feedback that non-linearly reinforces and grows the pre-existing SST anomaly. What this may also mean is that pound for pound, the North Pacific Meridional Mode may be a more effective generator of El Nino than the SPMM and having a +NPMM/-SPMM is more favorable than -NPMM/+SPMM because the base of the NPMM is directly connected to the edge of the warm pool whereas the SPMM is confined to the eastern Eq Pacific, limiting its potential for non-linear feedback unless a strong or extraordinary El Nino like 1982, 1997, &/or 2015 is observed.


But the reason canonical niño attempts tend to fail nowadays is a result of the presently unfavorable seasonality of the AMM (WHEM-ITCZ/z-cell network) which favors the more modoki style evolution via westward shift of ambient WP exhaust.

But modoki-type evolutions don’t rely as much on constructive interference from the PMM when compared to the canonical type evolutions. In modoki style years during the present cycle of AMM seasonality (2009, 2006, 2004, 2002, etc) the strongest niños (2009, 2002, etc) tended to have lower PMMs, while the weakest niños (2004, 2007, etc) tended to have higher PMMs.

Which makes theoretical sense to me, with the AMM tending to trend positive into boreal autumn in conjunction with the seasonal equatorward movement of the Pacific ITCZ away from those +PMM waters favoring weaker EPAC convection relative to WPAC convection.
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#1353
Phil

Posted 03 July 2018 - 10:50 AM

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The EQ RWs suppress the thermocline most appreciably a few degrees from the equator but to reiterate once again, because of the anticyclonic wind stress curl generated from the westward current associated w/ these waves, it actually offsets the anomalous discharge promoted by an eastward flowing equatorial current. This is an important connection to make because its related to the discharge-recharge hypothesis that explains why westward flowing currents and surface winds in La Nina charge the Eq Pacific w/ warm water and limit poleward discharge. Similarly westward propagating, slower moving Eq Rossby Waves generated by downwelling KW activity also offset the poleward discharge during NINOs which is a crucial mechanism that terminates them. There's lots of literature on this topic.


Except that assumes a relatively balanced bihemispheric diffraction of the OKW into ERWs (which often isn’t the case under anomalous MM regimes) and the stresses in question are only present underneath the ERW trail itself, not the entire basin (in the absence of additional OKW activity).

And either way, it’s still not structurally comparable to the state of transfer under the initial downwelling OKW, where off-equator water mass is falling equatorward, which is not true to the same extent after the formation of the ERW(s).

Not to mention any potential constructive/destructive interference from peripheral forcings on atmospheric circulation. These events all evolve uniquely (to state the obvious). If they didn’t, predicting ENSO would be a cakewalk.

As far as the PMM is concerned, you're really getting into a chicken-egg argument here. Again the PMM is generated by cumulative mid-latitude RW activity in the preceding winter that leaves a seasonal footprint which persists into the following spring. The depth of the anomalous warming associated w/ a PMM isn't as important as the surface reflection which affects low-level trades in the central and NE subtropical Pacific, you can easily have instances where it doesn't extend to an appreciable depth yet still yields similar forcing, additionally the mixed layer isn't that deep at this time of the year there barring the occasional TC so it likely won't matter all that much. The tropical forcing component from the warm pool is only one component to that RW activity which creates the PMM.


I agree re: equatorward cyclonic breakers aiding in the generation the PMM signature, but the extent to which occurs and sustains depends on a reduction in subtropical NH trades/poleward-displaced NPAC high. The +PMM could not occur without it. And the those boundary conditions are all produced by peripherally-initiated and/or nonlinear regional dynamics that modulate the ventilation of the warm pool.

I’m personally not aware of any +PMM trigger that doesn’t run through the Indo-Pacific warm pool first. If you know of any, I’d be very interested in learning about them. :)

The ITCZ is pushed poleward of its climatological position only in the eastern Pacific during +PMM, whereas because the base of the PMM extends directly onto the equator in the central Pacific the ITCZ actually remains close to the equator near the edge of the warmpool where non-linear feedbacks can take over and reinforce the SST anomaly and remotely force +SSTAs in the EP thru WWBs. (remote SST forcing component is larger than the local piece in the EP). The ITCZ juxtaposition in the Eastern Pacific doesn't matter as much because non-linear convective feedbacks don't occur here except in the strongest El Ninos, this is exactly why most weak EP-based NINOs in the modern era have failed as stated earlier.


But since we’re in a climate regime of post-solstice AMM increases (tied to changes in WP exhaust and other climate changes), in conjunction w/ the +PMM, it should become increasingly hostile to +ENSO as the ITCZ tries to migrate equatorward thru boreal autumn, as there’s an increasing off-equator component to the convention between 150W to 40W.
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#1354
Phil

Posted 03 July 2018 - 11:06 AM

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Just so there’s no misunderstanding, I’m not expecting a collapse to cold neutral like 2012/13.

I think we’ll see the weak niño head fake during the second half of summer into early autumn (in terms of ONI) with a return to neutral or warm neutral during the late autumn and winter.
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#1355
Webberweather53

Posted 03 July 2018 - 07:30 PM

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But the reason canonical niño attempts tend to fail nowadays is a result of the presently unfavorable seasonality of the AMM (WHEM-ITCZ/z-cell network) which favors the more modoki style evolution via westward shift of ambient WP exhaust.

But modoki-type evolutions don’t rely as much on constructive interference from the PMM when compared to the canonical type evolutions. In modoki style years during the present cycle of AMM seasonality (2009, 2006, 2004, 2002, etc) the strongest niños (2009, 2002, etc) tended to have lower PMMs, while the weakest niños (2004, 2007, etc) tended to have higher PMMs.

Which makes theoretical sense to me, with the AMM tending to trend positive into boreal autumn in conjunction with the seasonal equatorward movement of the Pacific ITCZ away from those +PMM waters favoring weaker EPAC convection relative to WPAC convection.

 

 

Not necessarily, this year's AMM set the bar lower than it ever has been, tanking to new record lows this past month (and almost for any month for that matter), we're not living in the 1995-2012 regime anymore for the time being so the first argument seems irrelevant.

 

This second statement doesn't make any sense whatsoever. If you actually read through the literature I've linked earlier you'd find that modoki evolutions actually do rely more on the PMM compared to canonical events because the north pacific meridional mode only significantly affects equatorial variability in the central Pacific because the base of the NPMM crosses the Eq Pacific near the dateline. The NPMM actually has little impact on the EP SST evolution and canonical events, this is reserved for the SPMM. Again, read the literature I sent you (please)...

 

The first bolded statement is true mainly because it's simply harder to generate higher SSTAs when the Equatorial Pacific is already stupid warm in a stronger event, obviously 2015-16 is a monstrous outlier that needs to be given due consideration.

The AMM really can't get any lower than it is now, a positive trend into this autumn (even a significant one) from where we stand now would still leave us with a very significant negative regime that's still not hostile to +ENSO.

 

 

Except that assumes a relatively balanced bihemispheric diffraction of the OKW into ERWs (which often isn’t the case under anomalous MM regimes) and the stresses in question are only present underneath the ERW trail itself, not the entire basin (in the absence of additional OKW activity).

And either way, it’s still not structurally comparable to the state of transfer under the initial downwelling OKW, where off-equator water mass is falling equatorward, which is not true to the same extent after the formation of the ERW(s).

Not to mention any potential constructive/destructive interference from peripheral forcings on atmospheric circulation. These events all evolve uniquely (to state the obvious). If they didn’t, predicting ENSO would be a cakewalk.


I agree re: equatorward cyclonic breakers aiding in the generation the PMM signature, but the extent to which occurs and sustains depends on a reduction in subtropical NH trades/poleward-displaced NPAC high. The +PMM could not occur without it. And the those boundary conditions are all produced by peripherally-initiated and/or nonlinear regional dynamics that modulate the ventilation of the warm pool.

I’m personally not aware of any +PMM trigger that doesn’t run through the Indo-Pacific warm pool first. If you know of any, I’d be very interested in learning about them. :)



But since we’re in a climate regime of post-solstice AMM increases (tied to changes in WP exhaust and other climate changes), in conjunction w/ the +PMM, it should become increasingly hostile to +ENSO as the ITCZ tries to migrate equatorward thru boreal autumn, as there’s an increasing off-equator component to the convention between 150W to 40W.

 

 

No it doesn't... The stresses actually become do become nearly basin wide in cases like this where one Kelvin Wave after the other is impinging on the eastern boundary region and reflecting into downwelling Rossby Wave. Rossby Wave wavelengths and slower phase speeds allow for much higher wavenumbers w/ Eq RWs, creating more or less traffic jams in the off-equatorial Pacific esp when compared to Kelvin Waves. Unless you're going to complete dismantle Sverdrup theory, none of this negates the fact that these RWs significantly hinder enhanced equatorial discharge associated w/ positive wind stress curl induced by the equatorial westerly wind anomalies.

 

This seems to be a common misconception amongst many tropical gurus, forcing is not a one way street, the mid-latitudes and tropics evolve together (Paul Roundy has done a lot of working on this) which means  everything will NOT go thru the Indo-WP warm pool and vis versa in the mid-latitudes. It's certainly an important player and arguably the most important globally but intrinsic mid-latitude variability and external forcing that's selectively expressed by the polar region are good examples wherein the forcing doesn't go thru the warm pool. You want an example, fine how about a +NAM forced in part externally via a major solar proton event that destroys a ton of ozone, cooling the polar stratosphere, ultimately favoring poleward circumglobal, poleward anticyclones as the stratospheric height and temperature anomalies descend into the troposphere w/ one of the major AO poles in the far NP, this would in essence favor stronger and potentially poleward displaced Aleutian ridging.

 

The problem with the last statement is this did not happen this year w/ the AMM, if anything the opposite has occurred and the AMM has tanked to new record lows since the last solstice, maybe next year a large-scale change may be afoot. The overwhelming majority of the ENSO convective footprint is west of 150W, I still don't see how that's going to matter here wrt total probability of an El Nino although again it will probably impact the strength and type of event we see which is what the literature shows.

 

Dan Vimont: "Wow - the AMM is the most negative it has ever been for June (-2.5 sigma for June), and the third most negative value since 1948. Meanwhile, the PMM is large and positive. The spatial SST structure is "as AMM as it gets"

 

https://twitter.com/...878561353207809



#1356
Webberweather53

Posted 03 July 2018 - 07:39 PM

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Just so there’s no misunderstanding, I’m not expecting a collapse to cold neutral like 2012/13.

I think we’ll see the weak niño head fake during the second half of summer into early autumn (in terms of ONI) with a return to neutral or warm neutral during the late autumn and winter.

 

Sorry but I have to strongly disagree with you. Unless the Atlantic warms up more than it ever has in the satellite era later this autumn to counteract the record low -AMM currently in place (good luck w/ that) and we see no additional sub seasonal help following the surge in NINO forcing late in July & August (also not terribly likely), I don't see this panning out. A weak-moderate modoki El Nino seems far more likely in 2018-19 w/ another NINO attempt potentially looming in 2019-20.


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#1357
Phil

Posted 03 July 2018 - 08:31 PM

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Not necessarily, this year's AMM set the bar lower than it ever has been, tanking to new record lows this past month (and almost for any month for that matter), we're not living in the 1995-2012 regime anymore for the time being so the first argument seems irrelevant.

This second statement doesn't make any sense whatsoever. If you actually read through the literature I've linked earlier you'd find that modoki evolutions actually do rely more on the PMM compared to canonical events because the north pacific meridional mode only significantly affects equatorial variability in the central Pacific because the base of the NPMM crosses the Eq Pacific near the dateline. The NPMM actually has little impact on the EP SST evolution and canonical events, this is reserved for the SPMM. Again, read the literature I sent you (please)...


Thanks for the response. I actually have read most the aforementioned literature. The difference is that I’ve elected to confine my reference period only to years after 1995, until it can be ascertained that the seasonality of the AMM/WHEM-ITCZ system has indeed changed.

This is what I’m referring to. Note the difference in the AMM/AMO sign in late summer/autumn vs spring. The seasonality is just as important as the sign itself in determining where the system state is headed. This ties right into the z-cell changes and failure of the more canonical niño progressions in recent decades.

SQtOJ1l.jpg
NlVLAfk.jpg

As for the PMM, when isolating my base period to the period from 1995-present, there is actually a weak inverse correlation between the sign of the PMM and the ONI (during +ENSO years). Meanwhile, the opposite seems to be true in -ENSO years.

No it doesn't... The stresses actually become do become nearly basin wide in cases like this where one Kelvin Wave after the other is impinging on the eastern boundary region and reflecting into downwelling Rossby Wave.


This is what I was asking you yesterday with my aloof “backslosh” comment. So I take it you believe the weaker OKW near the dateline has enough inertia behind it to perpetuate the downwelling process east of 150W after the bigger OKW diffracts into its ERW cycle later this month?

That’s what I’m skeptical of, in the absence of WWB activity west of ~140W or so.

Rossby Wave wavelengths and slower phase speeds allow for much higher wavenumbers w/ Eq RWs, creating more or less traffic jams in the off-equatorial Pacific esp when compared to Kelvin Waves. Unless you're going to complete dismantle Sverdrup theory, none of this negates the fact that these RWs significantly hinder enhanced equatorial discharge associated w/ positive wind stress curl induced by the equatorial westerly wind anomalies.


As far as I’m aware, it’s the returning easterly zonal current that is “hindered” by the ERW mechanics. But you’re still evacuating water mass poleward from the equator during the diffraction process, which aids upwelling/vertical overturning in the absence of follow-up OKW activity.

This seems to be a common misconception amongst many tropical gurus, forcing is not a one way street, the mid-latitudes and tropics evolve together (Paul Roundy has done a lot of working on this) which means everything will NOT go thru the Indo-WP warm pool and vis versa in the mid-latitudes. It's certainly an important player and arguably the most important globally but intrinsic mid-latitude variability and external forcing that's selectively expressed by the polar region are good examples wherein the forcing doesn't go thru the warm pool. You want an example, fine how about a +NAM forced in part externally via a major solar proton event that destroys a ton of ozone, cooling the polar stratosphere, ultimately favoring poleward circumglobal, poleward anticyclones as the stratospheric height and temperature anomalies descend into the troposphere w/ one of the major AO poles in the far NP, this would in essence favor stronger and potentially poleward displaced Aleutian ridging.


Nice post here. So, I agree with you re: external forcings on the tropics (which includes the warm pool)..otherwise it’s very difficult (if not impossible) to explain some of the correlations between ENSO dynamics and solar forcing(s). Too much there to be a coincidence.

However, I’m only referring to the maintenance of a PMM signature. I think it’s obvious that the slew of external forcings (I can think of dozens) aiding the RWB/PMM structure do so via a lower frequency modulation of warm pool structure and ventilation at trigger points. There are obvious correlations between the structure of the warm pool and the PMM/AMM. Very coherent ones. There are a number of cases where the warm pool structure refused to give way and the PMM failed to reverse.

The problem with the last statement is this did not happen this year w/ the AMM, if anything the opposite has occurred and the AMM has tanked to new record lows since the last solstice, maybe next year a large-scale change may be afoot. The overwhelming majority of the ENSO convective footprint is west of 150W, I still don't see how that's going to matter here wrt total probability of an El Nino although again it will probably impact the strength and type of event we see which is what the literature shows.


If we fail to walk back towards neutral/positive AMM this year, then yeah, my ENSO forecast could bust. I’m betting on recent climo tendencies here..a reversal in this AMM tendency would be huge, and would definitely have climate consequences as well. So I’m not ready to throw my chips in yet. ;)
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#1358
Phil

Posted 03 July 2018 - 08:43 PM

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Sorry but I have to strongly disagree with you. Unless the Atlantic warms up more than it ever has in the satellite era later this autumn to counteract the record low -AMM currently in place (good luck w/ that) and we see no additional sub seasonal help following the surge in NINO forcing late in July & August (also not terribly likely), I don't see this panning out. A weak-moderate modoki El Nino seems far more likely in 2018-19 w/ another NINO attempt potentially looming in 2019-20.


I agree re: 2019/20. Will be interesting to watch unfold.

In the end, we’re really only 6 months apart here..my guess is the move to Niño begins JFM 2019 following an early-season SSW/MJO event around Christmas, you seem to think it will establish during ASO of this year. That’s really not very different in the grand scheme of things. 🤓
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#1359
Webberweather53

Posted 03 July 2018 - 10:36 PM

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Thanks for the response. I actually have read most the aforementioned literature. The difference is that I’ve elected to confine my reference period only to years after 1995, until it can be ascertained that the seasonality of the AMM/WHEM-ITCZ system has indeed changed.

This is what I’m referring to. Note the difference in the AMM/AMO sign in late summer/autumn vs spring. The seasonality is just as important as the sign itself in determining where the system state is headed. This ties right into the z-cell changes and failure of the more canonical niño progressions in recent decades.

SQtOJ1l.jpg
NlVLAfk.jpg

As for the PMM, when isolating my base period to the period from 1995-present, there is actually a weak inverse correlation between the sign of the PMM and the ONI (during +ENSO years). Meanwhile, the opposite seems to be true in -ENSO years.


This is what I was asking you yesterday with my aloof “backslosh” comment. So I take it you believe the weaker OKW near the dateline has enough inertia behind it to perpetuate the downwelling process east of 150W after the bigger OKW diffracts into its ERW cycle later this month?

That’s what I’m skeptical of, in the absence of WWB activity west of ~140W or so.


As far as I’m aware, it’s the returning easterly zonal current that is “hindered” by the ERW mechanics. But you’re still evacuating water mass poleward from the equator during the diffraction process, which aids upwelling/vertical overturning in the absence of follow-up OKW activity.


Nice post here. So, I agree with you re: external forcings on the tropics (which includes the warm pool)..otherwise it’s very difficult (if not impossible) to explain some of the correlations between ENSO dynamics and solar forcing(s). Too much there to be a coincidence.

However, I’m only referring to the maintenance of a PMM signature. I think it’s obvious that the slew of external forcings (I can think of dozens) aiding the RWB/PMM structure do so via a lower frequency modulation of warm pool structure and ventilation at trigger points. There are obvious correlations between the structure of the warm pool and the PMM/AMM. Very coherent ones. There are a number of cases where the warm pool structure refused to give way and the PMM failed to reverse.


If we fail to walk back towards neutral/positive AMM this year, then yeah, my ENSO forecast could bust. I’m betting on recent climo tendencies here..a reversal in this AMM tendency would be huge, and would definitely have climate consequences as well. So I’m not ready to throw my chips in yet. ;)

 

No doubt there was a major step change in AMO-AMM behavior after 1995 but this year is a huge anomaly from just about everything we've seen since then w/ the latter (AMM) being in record low territory for crying out loud, I don't see this line of rationale being applicable here unless you firmly believe we're about to witness one of the most unreal turnarounds ever observed later this summer and autumn in the AMM/AMO. The downwelling KW crossing the CP will reinforce the already suppressed thermocline in the EP, even w/o it, we'd still have to contend w/ a warming Eq Pacific for the next 2-3 months at a minimum, even longer still for the central Pacific. I'm already seeing signs of low frequency coupling to the atmosphere & the next CCKW fixing to cross the Eq Pacific will be met with open arms.

 

chi200.cfs_.eqtr_.png

 

 

 

This seemingly weak downwelling wave has recently formed following the last round of intraseasonal forcing earlier this past month which didn't feature the classic, strong WWB, it's still in an area of the central-western Pacific where the thermocline slope is modest in comparison to further E (usually harder to generate subsurface anomalies as a result) and I stated before, I expect the next bout of sub seasonal forcing late in July into August to intensify this downwelling KW before it hits the eastern boundary region in September, so it probably won't look quite as weak down the road if we get a renewed slackening of the easterly trades which is usually all that's needed at this stage in the game for a weak-moderate El Nino.

 

 

I honestly don't see what's so bad about the cumulative U wind forcing over the Eq Pacific. Let me remind you that 2009 (shown below) had no significant dateline WWBs up to this point in time and still went on to produce a borderline strong El Nino w/ a very similar subsurface look to this year.

 

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

 

 

 

Now look at this year, we just had a very sizable WWB east of the dateline earlier this month from this last round of sub seasonal forcing & we're still reeling from the big MJO event this past February that helped set this all into motion.

 

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

 

2006-07 went onto produce a weak NINO event, no signs of let up w/ strong easterlies dominating right up to this point in July,

surely you have to believe this year wouldn't go onto produce an El Nino would it? Or better yet that we somehow aren't any worse off than either 2006-07 & 2009-10 in the WWB forcing department.

 

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

 

 

2014-15 lots of nearly continuous WWB activity early reminiscent of extraordinary El Ninos, only a couple easterly trade bursts near the dateline was all it took to set this back to a weak event. The cumulative U wind forcing was impressive yet we ended up w/ a weaker El Nino than 2009-10 that observed incessant dateline easterlies thru the summer.

75.184.9.71.184.0.20.8.png

 

 

1994-95, you certainly wouldn't know by looking at U850 anomalies that a borderline weak-moderate El Nino was coming

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

 

 

By now you should get my point. This year isn't doing anywhere near as bad you're claiming it to be wrt WWB forcing in the Eq Pacific so far esp when you compare it to other successful weak-moderate and even borderline strong El Ninos up to this point in time. October and beyond though is typically when most of these events pick up the pace and we would certainly need to see more sustained WWB activity but there's plenty of time for that to occur.

 

Yeah I was about to say, tbh your +PMM comments took me for a tailspin because it made it seem like you were really out of touch w/ reality here given the huge -AMM in place right now. 

 

"If we fail to walk back towards neutral/positive AMM this year, then yeah, my ENSO forecast could bust. I’m betting on recent climo tendencies here..a reversal in this AMM tendency would be huge, and would definitely have climate consequences as well. So I’m not ready to throw my chips in yet."

 

Wow, you're being conservative here to say the least wrt clinging to your initial forecast based on AMM evolution. Like Dan Vimont said, you really can't get more -AMM than this. If your NINO head fake is hinging on the AMM flipping around positive or even going neutral in just 2-3 months, I'm sorry but I don't know what to tell you other than you're probably screwed.

atl.gif

 

compday.T3WWula5eG.gif



#1360
Phil

Posted 05 July 2018 - 01:15 PM

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No doubt there was a major step change in AMO-AMM behavior after 1995 but this year is a huge anomaly from just about everything we've seen since then w/ the latter (AMM) being in record low territory for crying out loud, I don't see this line of rationale being applicable here unless you firmly believe we're about to witness one of the most unreal turnarounds ever observed later this summer and autumn in the AMM/AMO.


Sorry for the late reply. Busy 4th for me.

This (1990s-present) seasonality in the AMM/AMO is a result of very large scale, inertia-loaded processes in the atmosphere-ocean system that would be very hard to reverse in just one year. Look at what happened back in 1989 for an example of the inception of this situation..if the atmospheric circulation (anticyclonic breaker train) that maintains the -AMM is killed off every summer/fall by changes to WP exhaust/z-cell climatology, then for all intents and purposes you lose the -AMM as a forcing until the termination of the Eurasian monsoonal trough.

We’re already beginning to see the peripherally forced seasonality in the WHEM circulation affect the AMM. Over the last month (7/3/18 relative to 6/3/18):

iEuUBNf.gif

So despite the *present* sign (of (-)AMM), if you’re losing it to destructive off-domain interference, your system state isn’t a -AMM system state to begin with because the origin of spatial radiance is elsewhere.

The downwelling KW crossing the CP will reinforce the already suppressed thermocline in the EP, even w/o it, we'd still have to contend w/ a warming Eq Pacific for the next 2-3 months at a minimum, even longer still for the central Pacific. I'm already seeing signs of low frequency coupling to the atmosphere & the next CCKW fixing to cross the Eq Pacific will be met with open arms.

chi200.cfs_.eqtr_.png

This seemingly weak downwelling wave has recently formed following the last round of intraseasonal forcing earlier this past month which didn't feature the classic, strong WWB, it's still in an area of the central-western Pacific where the thermocline slope is modest in comparison to further E (usually harder to generate subsurface anomalies as a result) and I stated before, I expect the next bout of sub seasonal forcing late in July into August to intensify this downwelling KW before it hits the eastern boundary region in September, so it probably won't look quite as weak down the road if we get a renewed slackening of the easterly trades which is usually all that's needed at this stage in the game for a weak-moderate El Nino.

I honestly don't see what's so bad about the cumulative U wind forcing over the Eq Pacific. Let me remind you that 2009 (shown below) had no significant dateline WWBs up to this point in time and still went on to produce a borderline strong El Nino w/ a very similar subsurface look to this year.

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

Now look at this year, we just had a very sizable WWB east of the dateline earlier this month from this last round of sub seasonal forcing & we're still reeling from the big MJO event this past February that helped set this all into motion.

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

2006-07 went onto produce a weak NINO event, no signs of let up w/ strong easterlies dominating right up to this point in July,
surely you have to believe this year wouldn't go onto produce an El Nino would it? Or better yet that we somehow aren't any worse off than either 2006-07 & 2009-10 in the WWB forcing department.

2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.


2014-15 lots of nearly continuous WWB activity early reminiscent of extraordinary El Ninos, only a couple easterly trade bursts near the dateline was all it took to set this back to a weak event. The cumulative U wind forcing was impressive yet we ended up w/ a weaker El Nino than 2009-10 that observed incessant dateline easterlies thru the summer.
75.184.9.71.184.0.20.8.png

1994-95, you certainly wouldn't know by looking at U850 anomalies that a borderline weak-moderate El Nino was coming
2606-a000-1500-a0c9-9457-afaf-7d0d-6ae5.

By now you should get my point. This year isn't doing anywhere near as bad you're claiming it to be wrt WWB forcing in the Eq Pacific so far esp when you compare it to other successful weak-moderate and even borderline strong El Ninos up to this point in time. October and beyond though is typically when most of these events pick up the pace and we would certainly need to see more sustained WWB activity but there's plenty of time for that to occur.

Yeah I was about to say, tbh your +PMM comments took me for a tailspin because it made it seem like you were really out of touch w/ reality here given the huge -AMM in place right now.

"If we fail to walk back towards neutral/positive AMM this year, then yeah, my ENSO forecast could bust. I’m betting on recent climo tendencies here..a reversal in this AMM tendency would be huge, and would definitely have climate consequences as well. So I’m not ready to throw my chips in yet."

Wow, you're being conservative here to say the least wrt clinging to your initial forecast based on AMM evolution. Like Dan Vimont said, you really can't get more -AMM than this. If your NINO head fake is hinging on the AMM flipping around positive or even going neutral in just 2-3 months, I'm sorry but I don't know what to tell you other than you're probably screwed.
atl.gif

compday.T3WWula5eG.gif


A few points.

1) The CFSv2 (and the vast majority climate model guidance,, tbh) almost always over-estimates low-frequency coupling to projected SSTAs at the expense of intraseasonal variability. I pay zero attention to those VP/OLR model projections outside of ENSO/low-freq situations that are already established.

2) I care less about where the AMM/U-winds/etc are right now, as opposed to where they’re going, and why. In this case, why would I extrapolate from a -AMM/OKW state that lacks discernible constructive interference in the derivations? When the climatology of the circulatory seasonality for the last two decades vehemently opposes extrapolations from a static state, that’s a huge red flag in my book.

3) There is no niño without additional warm pool discharge/OKW activity prominent enough to overcome intraseasonal forcing and the inertia of the thermocline return (currently timed for early September in the absence of said additional OKW activity). Without it, you necessarily lose ground. Climate models projecting a low frequency coupling is typical for pseudo-emergent states with some structural homogeneity to their programmed climatological EOFs. The model projections don’t impress me at all, tbh.
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#1361
Phil

Posted 05 July 2018 - 02:23 PM

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Notice how the aforementioned El Niños of 1994, 2002, 2006, and 2009 occurred because of subsequent WWB activity along/west of the dateline after the summer solstice, hindering Indonesian throughflow.

And the tendency is always towards increasing WWB activity from boreal winter/spring to boreal autumn/winter, rather than the opposite.

wzcKx8Z.jpg
Q6oB7Lv.jpg
SjSuORx.jpg
NfvachF.jpg

This is a climatological bedrock of niño years during this multidecadal regime of seasonality that initiated during the 1990s/anti-canonical era.
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#1362
Phil

Posted 05 July 2018 - 02:41 PM

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Meanwhile, +PMM years that lose ground in ONI after the fall equinox (AKA “head fake” years) tend to feature the opposite tendency, with strong WWB activity during boreal winter/spring then a walk-back during summer/autumn.

For example, look at 2014. It was “technically” a niño, albeit barely (since it started from a more +ENSO background state) but it still lost ground during boreal winter, and SSTs fell below Niño threshold for a significant period of time.

This year reminds me of 2014, in the sense that we had the significant WWB activity in J/F/M, which extended to/beyond the dateline, followed by a retraction during the subsequent months.

Here is 2014:

O5OITYS.jpg

And here is 2018 so far. These two years share the structural homogeneity for “head fake” events.

NSJeaV5.jpg
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#1363
Webberweather53

Posted 06 July 2018 - 04:45 AM

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That’s still a neutral AMM change over the last month, sure the last few decades and esp the 2010s have featured rapidly ascending AMM regimes but why do you think it doesn’t matter what the current AMM state is now? I Why do you think we’re in the same regime as 1995-2012 era when it’s blatantly obvious we’re not after the 2015-16 NIno w/ a cold Atlantic and Indian Ocean? The same interannual variability and AMM behavior evident over the past few decades isn’t as applicable here as you’re touting it to be. I think you’re grasping at straws here because this is a RECORD negative regime, it will take a miracle to bring it back significantly into positive territory and we have made no progress whatsoever in the last month or so as the SST graphic you posted shows with the South Atlantic continuing to disproportionately warm compared to the North Atlantic, so the AMM grows more negative still. It definitely matters where we’re starting here lol. Both the CFSv2 and EPS show low frequency coupling beginning within the next 1-2 weeks and/or are already initializing it over the Pacific basin, do you really believe ALL the models are that bad, again I think you’re stretching it here. Additionally, you’re still clinging to this nonsense that we aren’t drawing from the warmpool, I guess you don’t see the obvious downwelling KW passing the dateline in the CPC analyses (even if its a weak wave). Integrated warm water volume east of the dateline is 5th highest on record for June, for the most part we’re only behind strong El Niños like 1997, 2015, 1991, etc and have more WWV in the EP than the peaks of recent weak El Ninos. There’s multiple ways to get to the same answer and we are still ahead of those years in terms of cumulative forcing. It’s also probably not a good idea to blindly assume there won’t be anymore significant WWB forcing for the remainder of the summer as we saw in 2014 with tropical forcing shifting back towards the Pacific and W hem later this month.

#1364
Webberweather53

Posted 06 July 2018 - 05:11 AM

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CFSv2 day 1-5 forecast on Carl Schreck’s site already shows low frequency coupling (purple contours) over the Pacific... Sorry but I seriously doubt all the models are going to be that unreliable s.t they can’t get the forecast remotely correct just several days out, again I think you’re really making a stretch here.

#1365
Phil

Posted 06 July 2018 - 11:26 AM

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That’s still a neutral AMM change over the last month, sure the last few decades and esp the 2010s have featured rapidly ascending AMM regimes but why do you think it doesn’t matter what the current AMM state is now? I Why do you think we’re in the same regime as 1995-2012 era when it’s blatantly obvious we’re not after the 2015-16 NIno w/ a cold Atlantic and Indian Ocean? The same interannual variability and AMM behavior evident over the past few decades isn’t as applicable here as you’re touting it to be. I think you’re grasping at straws here because this is a RECORD negative regime, it will take a miracle to bring it back significantly into positive territory and we have made no progress whatsoever in the last month or so as the SST graphic you posted shows with the South Atlantic continuing to disproportionately warm compared to the North Atlantic, so the AMM grows more negative still.


1) I’m not saying the AMM will wildly swing back into super positive territory. Too much thermal inertia for that. But my guess is that it recovers to neutral or weakly positive. The seasonality matters, again, because of what’s driving it. The -AMM is not favored in recent decades during the monsoonal forcing/warm season circulation state. It yields to the west-Pacific/IPWP under an increasingly axisymmetric forcing/HC regime that flips the NAO to negative during August and September most years.

It definitely matters where we’re starting here lol. Both the CFSv2 and EPS show low frequency coupling beginning within the next 1-2 weeks and/or are already initializing it over the Pacific basin, do you really believe ALL the models are that bad, again I think you’re stretching it here.


What are you using for a low-freq filter of the EPS? I’m seeing plenty of intraseasonal variability amongst the ensemble members, albeit the degrees vary too. Usually the safe bet (IMO) is during the warm season is to go bullish on the projected intraseasonal components and bearish on the projected low-freq components, in the absence of any pre-established low-freq regime (of which there has been none...yet).

And yeah (especially during the warm season) models are catastrophically awful at picking up intraseasonal forcing at-range. Especially the CFSv2. I never even look at the CFSv2 anymore..it’s an over-parameterized piece of junk in my book.

I’ve never seen the CFSv2 it pick up intraseasonal variability accurately beyond ~ 3 weeks during the warm season. Ever. If you can show me otherwise, I’d be shocked.

Additionally, you’re still clinging to this nonsense that we aren’t drawing from the warmpool, I guess you don’t see the obvious downwelling KW passing the dateline in the CPC analyses (even if its a weak wave). Integrated warm water volume east of the dateline is 5th highest on record for June, for the most part we’re only behind strong El Niños like 1997, 2015, 1991, etc and have more WWV in the EP than the peaks of recent weak El Ninos.


It’s not just that it’s a weak wave..but it’s much weaker than the one before it. That’s the problem I see (in the absence of additional WWB/OKW activity), because the thermocline return will be loaded with fluid inertia given the strength of the first wave, and a weak, impotent OKW alone won’t be enough without additional support, IMO.

There’s multiple ways to get to the same answer and we are still ahead of those years in terms of cumulative forcing. It’s also probably not a good idea to blindly assume there won’t be anymore significant WWB forcing for the remainder of the summer as we saw in 2014 with tropical forcing shifting back towards the Pacific and W hem later this month.


The subsequent WWB activity/dateline forcing is indeed what I’m watching for. The last round of intraseasonal forcing kind of circumvented the WPAC/dateline area due to emergent monsoonal dynamics and an outrageous amount of poleward +AAM propagation.

That’s not something you typically see in developing Niño years (can’t find any cases of it). If the next intraseasonal cycle fails to remain coherent through the dateline and/or flip U-winds west of the dateline for a prolonged period of time..then it would statistically preclude a niño since no non-canonical niño has ever failed to produce WWBs after mid-July.
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#1366
Webberweather53

Posted 06 July 2018 - 12:11 PM

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1) I’m not saying the AMM will wildly swing back into super positive territory. Too much thermal inertia for that. But my guess is that it recovers to neutral or weakly positive. The seasonality matters, again, because of what’s driving it. The -AMM is not favored in recent decades during the monsoonal forcing/warm season circulation state. It yields to the west-Pacific/IPWP under an increasingly axisymmetric forcing/HC regime that flips the NAO to negative during August and September most years.

What are you using for a low-freq filter of the EPS? I’m seeing plenty of intraseasonal variability amongst the ensemble members, albeit the degrees vary too. Usually the safe bet (IMO) is during the warm season is to go bullish on the projected intraseasonal components and bearish on the projected low-freq components, in the absence of any pre-established low-freq regime (of which there has been none...yet).
And yeah (especially during the warm season) models are catastrophically awful at picking up intraseasonal forcing at-range. Especially the CFSv2. I never even look at the CFSv2 anymore..it’s an over-parameterized piece of junk in my book.
I’ve never seen the CFSv2 it pick up intraseasonal variability accurately beyond ~ 3 weeks during the warm season. Ever. If you can show me otherwise, I’d be shocked.

It’s not just that it’s a weak wave..but it’s much weaker than the one before it. That’s the problem I see (in the absence of additional WWB/OKW activity), because the thermocline return will be loaded with fluid inertia given the strength of the first wave, and a weak, impotent OKW alone won’t be enough without additional support, IMO.

The subsequent WWB activity/dateline forcing is indeed what I’m watching for. The last round of intraseasonal forcing kind of circumvented the WPAC/dateline area due to emergent monsoonal dynamics and an outrageous amount of poleward +AAM propagation.
That’s not something you typically see in developing Niño years (can’t find any cases of it). If the next intraseasonal cycle fails to remain coherent through the dateline and/or flip U-winds west of the dateline for a prolonged period of time..then it would statistically preclude a niño since no non-canonical niño has ever failed to produce WWBs after mid-July.


But we’re not talking about intraseaonal variability beyond 2-3 weeks from now, I have specifically said over and over again that this forecast is inside 1-2 weeks, in fact inside 1-5 days is when the VP200 will envelope onto the entire basin. Sure you’re not claiming it will become raging or significantly positive but what makes you think it’ll even go to neutral anytime soon because the graphic up showed earlier only showed an intensifying -AMM with the southern Atlantic warming more than the north, I honestly don’t know why you think we’re still in the post 1997-98 era globally and it’s similar to the last few decades because it’s obviously not with a cold Indian Ocean and a -AMO. I’d be very careful in assuming this because weve has seen this trend the past few decades so we’re automatically slated for a very substantial AMM recovery. Even if the AMM recovers a lot it still may be negative and significantly at that. Quite frankly I don’t think you understand that this year will have a bigger hill to climb than any other year ever observed before it, good luck, but hey at least you admitted that the initial state matters :) Its also nice to see you finally came to your sense and admitted we’re drawing from the warm pool after blatantly denying it for the past week or so :) the last Kelvin Wave was no slouch and this one while small will reinforce what’s already there, the warm water volume east of the dateline is actually ahead of all modern Niño head fakes atm, if we back off it won’t be anywhere near as easy as you think nor does a lack of subseasonal forcing in the next month or so automatically preclude a Nino as you’re claiming. Even though u may protest, we simply don’t have enough data to jump to conclusions like that, if there’s anything you should take away w/ ENSO it’s that the modern observed range of variability represents only an infinitesimal fraction of late Holocene variability that’s somewhat applicable to modern ENSO...

#1367
happ

Posted 06 July 2018 - 12:16 PM

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Sitting at the feet of professors - love the discussion  B)


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#1368
Phil

Posted 06 July 2018 - 12:24 PM

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Re: Hurricane Beryl, the AMM, and ITCZ width. Not the most prolific CCKW, but Beryl’s latitude is exceptionally low, more towards those warmer near-equator waters underneath the cold horseshoe.

I wonder if this will be a season with relatively fewer recurvatures (and fewer storms altogether) but produce a few equatorward-shifted MDR-style genesis events along with the more-favored homebrew stuff (given off-eq EPAC ventilation).

I also think there’s a solid chance we’ll have a more delayed peak this year, towards the equinox into early October.
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#1369
weatherfan2012

Posted 06 July 2018 - 01:25 PM

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Re: Hurricane Beryl, the AMM, and ITCZ width. Not the most prolific CCKW, but Beryl’s latitude is exceptionally low, more towards those warmer near-equator waters underneath the cold horseshoe.
I wonder if this will be a season with relatively fewer recurvatures (and fewer storms altogether) but produce a few equatorward-shifted MDR-style genesis events along with the more-favored homebrew stuff (given off-eq EPAC ventilation).
I also think there’s a solid chance we’ll have a more delayed peak this year, towards the equinox into early October.

it will be interesting to see if we get an East coast tropica system hit this fall would be fitting.

#1370
Phil

Posted 06 July 2018 - 01:34 PM

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But we’re not talking about intraseaonal variability beyond 2-3 weeks from now, I have specifically said over and over again that this forecast is inside 1-2 weeks, in fact inside 1-5 days is when the VP200 will envelope onto the entire basin. Sure you’re not claiming it will become raging or significantly positive but what makes you think it’ll even go to neutral anytime soon because the graphic up showed earlier only showed an intensifying -AMM with the southern Atlantic warming more than the north, I honestly don’t know why you think we’re still in the post 1997-98 era globally and it’s similar to the last few decades because it’s obviously not with a cold Indian Ocean and a -AMO.


You can’t even calculate low-frequency components in such close range. You typically filter on a 30-day resolution for standing waves/etc. The CFSv2 is just losing the intraseasonal components after ~ 20 days, as it always does.

Regarding the 1998-2016 regime, we’re actually closer to agreeing than you realize. ;)

So, I agree that we’re terminating the 1998-2016 circulation regime (which was dominated by that “drinking bird” style function of resonance, as it relates to the derived seasonality of the annular modes under the west-shifted Pacific Hadley/Walker engine, with the effects of the enhanced Indonesian throughflow/warm IO completing the equator/pole feedback loop through the seasonal cycle, which is reflected by the meridional modes).

It was a period of broad z-cell expansion/off-equator heating as the mass circulation strengthened above the acisymmetric changes in tropopause height. It really contributed to climate warming as well, given the resulting weakening of the meridional temperature gradient and reduction in low latitude cloud cover, which will now begin to reverse over the next decade and possibly beyond.

The difference is, I don’t think we can accomplish this transition in just one year. There are a multitude of structurally-analogous transitions expressed clearly in the paleoclimate data (suggesting some structural homogeneity in the Holocene EOFs), however, the vast majority of them occurred over a decade or two. The last time we observed a single-year flip (of the matching sign and structure) was just before the 8200kr cooling event, back in the early part of the interglacial. It requires an extraordinary build-up of disequilibrium to produce such an outrageously fast reversal in such an inertially-laden system (of the suggested direction).

What you’re predicting is essentially a Bond event. And we definitely don’t want one of those.

I’d be very careful in assuming this because we’ve seen this trend the past few decades so we’re automatically slated for a very substantial AMM recovery. Even if the AMM recovers a lot it still may be negative and significantly at that. Quite frankly I don’t think you understand that this year will have a bigger hill to climb than any other year ever observed before it, good luck, but hey at least you admitted that the initial state matters :) Its also nice to see you finally came to your sense and admitted we’re drawing from the warm pool after blatantly denying it for the past week or so :) the last Kelvin Wave was no slouch and this one while small will reinforce what’s already there, the warm water volume east of the dateline is actually ahead of all modern Niño head fakes atm, if we back off it won’t be anywhere near as easy as you think nor does a lack of subseasonal forcing in the next month or so automatically preclude a Nino as you’re claiming. Even though u may protest, we simply don’t have enough data to jump to conclusions like that, if there’s anything you should take away w/ ENSO it’s that the modern observed range of variability represents only an infinitesimal fraction of late Holocene variability that’s somewhat applicable to modern ENSO...


Well again, it’s not that I’m just assuming we’ll follow recent climo w/ AMM. Rather, it’s the *reasons for the existence of* that seasonality that leads me to believe it won’t terminate in just one year, and *those reasons* also act on peripheral dynamics related to ENSO. Even if the sign is still neutral or somewhat negative.

FWIW, I never claimed we had zero draw from the warm pool. I just don’t think there’s enough of it. With the big OKW still in the EPAC, we’d still technically be “drawing from the warm pool”, even in the absence of the weak follow-up.

I’ll get more bullish on a niño if persistent westerly anomalies develop between 120E and the dateline by the end of August. If not, the chances of a niño drop to almost zero.
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#1371
Webberweather53

Posted 06 July 2018 - 03:29 PM

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You can’t even calculate low-frequency components in such close range. You typically filter on a 30-day resolution for standing waves/etc. The CFSv2 is just losing the intraseasonal components after ~ 20 days, as it always does.
Regarding the 1998-2016 regime, we’re actually closer to agreeing than you realize. ;)
So, I agree that we’re terminating the 1998-2016 circulation regime (which was dominated by that “drinking bird” style function of resonance, as it relates to the derived seasonality of the annular modes under the west-shifted Pacific Hadley/Walker engine, with the effects of the enhanced Indonesian throughflow/warm IO completing the equator/pole feedback loop through the seasonal cycle, which is reflected by the meridional modes).
It was a period of broad z-cell expansion/off-equator heating as the mass circulation strengthened above the acisymmetric changes in tropopause height. It really contributed to climate warming as well, given the resulting weakening of the meridional temperature gradient and reduction in low latitude cloud cover, which will now begin to reverse over the next decade and possibly beyond.
The difference is, I don’t think we can accomplish this transition in just one year. There are a multitude of structurally-analogous transitions expressed clearly in the paleoclimate data (suggesting some structural homogeneity in the Holocene EOFs), however, the vast majority of them occurred over a decade or two. The last time we observed a single-year flip (of the matching sign and structure) was just before the 8200kr cooling event, back in the early part of the interglacial. It requires an extraordinary build-up of disequilibrium to produce such an outrageously fast reversal in such an inertially-laden system (of the suggested direction).
What you’re predicting is essentially a Bond event. And we definitely don’t want one of those.

Well again, it’s not that I’m just assuming we’ll follow recent climo w/ AMM. Rather, it’s the *reasons for the existence of* that seasonality that leads me to believe it won’t terminate in just one year, and *those reasons* also act on peripheral dynamics related to ENSO. Even if the sign is still neutral or somewhat negative.
FWIW, I never claimed we had zero draw from the warm pool. I just don’t think there’s enough of it. With the big OKW still in the EPAC, we’d still technically be “drawing from the warm pool”, even in the absence of the weak follow-up.
I’ll get more bullish on a niño if persistent westerly anomalies develop between 120E and the dateline by the end of August. If not, the chances of a niño drop to almost zero.

CFSv2 initialization already shows low frequency -VP200 signal in the WP, it propagates ever so slightly east over the course of the month. U never claimed we had 0 draw from the warmpool you’re comments several days ago suggest otherwise, the fact that I had to convince u there was actually a downwelling KW in the CP should be your big clue but I’ll let you believe what u want :) As for this regime flip globally you’re taking it way out of context nor do I think you know what I’m really arguing here (which is normal for us tbh lol and me included as I often take things the wrong way haha) It’s fine to believe that the seasonality in the ITCZ contributing to AMM behavior but the long term climatological behavior of the monsoon is already somewhat factored in, you are going to need another mechanism to significantly flip it to neutral or positive. If it stays negative then that really defeats the purpose of one of your pillars for a Niño head fake, a less negative but still negative AMM is conducive to Nino development, you’re gonna need to look elsewhere if that transpires.
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#1372
Webberweather53

Posted 06 July 2018 - 03:46 PM

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But let’s say you’re right here and we fade to warm neutral then try to pull out an El Niño next year, talk about pulling a page once again out of the 19th-early 20th century ENSO playbook. I definitely see it happening if the AMM collapses to neutral but I’m very skeptical for obvious reasons because this regime really got going as early as last winter and we are sitting near record lows, only one way to go from here lol
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#1373
Webberweather53

Posted 06 July 2018 - 04:03 PM

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Re: Hurricane Beryl, the AMM, and ITCZ width. Not the most prolific CCKW, but Beryl’s latitude is exceptionally low, more towards those warmer near-equator waters underneath the cold horseshoe.
I wonder if this will be a season with relatively fewer recurvatures (and fewer storms altogether) but produce a few equatorward-shifted MDR-style genesis events along with the more-favored homebrew stuff (given off-eq EPAC ventilation).
I also think there’s a solid chance we’ll have a more delayed peak this year, towards the equinox into early October.

I agree with all of the above, I got a kick out of Dr Ventrice getting salty earlier today because he made another one of his infamous bold predictions expecting no TCs in the Atlantic in July lol. Literature shows cold AMOs favor lower latitude cyclones and less recurves (go figure because the Azores-Bermuda high is usually stronger in cases like this, if we had a solid Niña in place I’d probably be at least mildly concerned about the steering pattern (1985 for ex w/ a Niña, +PMM, -AMO)). You tend to see a lot of low latitude very intense TCs in the Caribbean, Gulf, & extreme SW Atlantic in the 2-3 years following multi-yr Niños in the cold AMO era. (1915, 1916, 1979, 1980, 1988, 1989, etc). Michael Lowry also showed a nice graphic several weeks ago showing that cold AMO years peak significantly later... The major caveat we have this year against 1970-1994 is an active AEW train and a wet Africa still seems to be a major player on the globe even after the 2015-16 Niño. Storms like Beryl even in a crappy environment are certainly more likely when the Sahel is wet, and you have stronger, more numerous AEWs...
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#1374
Webberweather53

Posted 06 July 2018 - 04:21 PM

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I just looked at the EPS U850 monthly product for the equatorial Pacific from over a month ago and I have to say I’m very impressed, the model correctly sniffed out the subseasonal forcing signal completely skipping the WP and the WWBs in the far eastern Pacific that occurred last month. Hopefully I can phone a friend in high places to let me have a peak at its opinion thru the end of August even though it should be taken with a grain of salt. The latest forecast I saw showed WWBs in the WP beginning in mid July so I guess we’ll see
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#1375
Phil

Posted 06 July 2018 - 04:23 PM

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Uhhh yea you can it’s called the other month before the next 5 day period maybe, initialization already shows low frequency -VP200 signal in the WP. Lol.


There has been no decipherable low frequency signal in the VP200 anomalies during the last 6 weeks. Can you show me otherwise?

There’s an intraseasonal wave responsible for the negative VP200 anomalies across the Indo-Pacific, but that’s opposite of the low frequency structure of developing Niños, which have positive VP200 anomalies there.

See our recent example cases for developing niños:

c2FUUFA.png

Versus modeling for the next 2 weeks:

TjHPcM0.png
BapaXF4.png

It just so happens that the GEFS/CFSv2 have a prolific bias towards this WHEM convection (as I’m sure you’re aware of) and it’s in the nature of seasonal guidance to over-couple to projected SSTAs at the expense of intraseasonal variability (I’m sure you’re aware of that too).

Yes, forcing should propagate eastward into the VP200 EOF for developing niños, but that doesn’t mean it will magically stop propagating and stay there. No, it will continue propagating and recycle. How much residual convection remains after the wave recycles is the question, IMO.

The CFSv2 abruptly shuts down the intraseasonal component, completely, over the span of 5 days, and keeps all anomalous convection locked in the EPAC/WHEM...that’s not going to happen :lol: You seldom see a switch flip like that even during high amplitude ENSO events. You could argue 1997 pulled it off, but what was during the equinox in a transition into a canonical style super niño, lol.

U never claimed we had 0 draw from the warmpool you’re comments several days ago suggest otherwise, the fact that I had to convince u there was actually a downwelling KW in the CP should be your big clue but I’ll let you believe what u want :)


If that’s how it came off, I apologize for the misleading phrasing. That certainly wasn’t the message I was trying to convey (that somehow there was zero warm pool draw..that would be stupid since it’s impossible not to have warm pool draw in the presence of a downwelling OKW of any kind).

As for this regime flip globally you’re taking it way out of context nor do I think you know what I’m really arguing here (which is normal for us tbh lol and me included as I often take things the wrong way haha) It’s fine to believe that the seasonality in the ITCZ contributing to AMM behavior but the long term climatological behavior of the monsoon is already somewhat factored in, you are going to need another mechanism to significantly flip it to neutral or positive. If it stays negative then that really defeats the purpose of one of your pillars for a Niño head fake, a less negative but still negative AMM is conducive to Nino development, you’re gonna need to look elsewhere if that transpires.


Haha, maybe so. Wouldn’t be the first time. ;)

Though I would vehemently argue that nothing in the climate system occurs in a vacuum..it’s all connected in one way or another. The AMM is no exception..a flip negative requires changes to large scale boundary conditions.

As for 2018, what I’m looking for re: AMM, is how much it recovers (if at all) during the next 6 months.

If the magnitude of the recovery (regardless of the sign of the index) is as large or larger than normal, that would indicate to me that boundary conditions are less favorable for a niño (which is what I expect).

If the AMM recovery is smaller, or (god forbid) nonexistent, then it would indicate a drastic reorganization of the climate system, a higher likelyhood of a niño, and probably a multidecadal shrinking of the IPWP, given the necessarily large amplitude of the trigger.
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#1376
Phil

Posted 06 July 2018 - 04:30 PM

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I just looked at the EPS U850 monthly product for the equatorial Pacific from over a month ago and I have to say I’m very impressed, the model correctly sniffed out the subseasonal forcing signal completely skipping the WP and the WWBs in the far eastern Pacific that occurred last month. Hopefully I can phone a friend in high places to let me have a peak at its opinion thru the end of August even though it should be taken with a grain of salt. The latest forecast I saw showed WWBs in the WP beginning in mid July so I guess we’ll see


Interesting. I’ll have to check it out. If the EPS is indeed suggesting low frequency EPAC/WHEM coupling, that is definitely a bigger deal than the CFSv2 suggesting it. Because the CFS/GEFS are always trying to throw convection into the WHEM. :lol:

Remember last year how Dr. Paul Roundy (whom I respect immensely) was constantly posting those images of the CFSv2 projecting a flip to westerlies across the eastern and central Pacific? Of course it never happened..fooled me too.
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#1377
Phil

Posted 06 July 2018 - 04:42 PM

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I agree with all of the above, I got a kick out of Dr Ventrice getting salty earlier today because he made another one of his infamous bold predictions expecting no TCs in the Atlantic in July lol. Literature shows cold AMOs favor lower latitude cyclones and less recurves (go figure because the Azores-Bermuda high is usually stronger in cases like this, if we had a solid Niña in place I’d probably be at least mildly concerned about the steering pattern (1985 for ex w/ a Niña, +PMM, -AMO)). You tend to see a lot of low latitude very intense TCs in the Caribbean, Gulf, & extreme SW Atlantic in the 2-3 years following multi-yr Niños in the cold AMO era. (1915, 1916, 1979, 1980, 1988, 1989, etc). Michael Lowry also showed a nice graphic several weeks ago showing that cold AMO years peak significantly later... The major caveat we have this year against 1970-1994 is an active AEW train and a wet Africa still seems to be a major player on the globe even after the 2015-16 Niño. Storms like Beryl even in a crappy environment are certainly more likely when the Sahel is wet, and you have stronger, more numerous AEWs...


I was about to ask you about that. I haven’t read enough about Sahel rainfall or hurricane activity in general to develop an informed opinion, but have you done abt research on the relationship between the Mascarene High/SIOD and Atlantic hurricane activity in the subsequent season? I feel like there’s something there but I haven’t had the time or motivation to dig into it.

And yeah, Dr. Ventrice was going for the Hail Mary with that one. :lol: If the system off the Carolinas develops, his forecast for a dead July will look pretty bad (though kudos to him for sticking his neck out there).
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#1378
Phil

Posted 06 July 2018 - 04:54 PM

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But let’s say you’re right here and we fade to warm neutral then try to pull out an El Niño next year, talk about pulling a page once again out of the 19th-early 20th century ENSO playbook. I definitely see it happening if the AMM collapses to neutral but I’m very skeptical for obvious reasons because this regime really got going as early as last winter and we are sitting near record lows, only one way to go from here lol


You have a point re: it being difficult to avoid some type of recovery in the AMM following record lows. So I’m not going to try and claim that I was “correct” if the recovery is modest. ;) Obviously I’m expecting something bigger, more similar to what happened in 1989. If I’m wrong I’ll be the first one to admit it.

And yeah, it would be interestino to repeat the “slow walk” to El Niño again, after it just happened in 2014. Might be time to consider the effects of low solar on ENSO tendencies (paleo data unanimously indicates that more frequent niños and +PDO/ weak Asian monsoons are the typical climatological responses to minimums in solar activity).
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#1379
Phil

Posted 06 July 2018 - 06:08 PM

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This is actually a pretty bizarre situation...it actually looks like the entire equatorial Pacific overturning cell has been knocked onto its side, creating the fabric of spatial dissonance. I think we’ll need to widen our 5*N/5*S hovmollers to accurately capture this!

The NH wavecycle is clearly way ahead of the SH. Note the westward retraction of the SH subsurface warmth bifurcating from the first OKW (which is already well into the EPAC) recharging that weak OKW in the WPAC, while the NH is just a massive OHC void propagating westward ahead of the initial OKW. So disorganized.

http://www.cpc.ncep....y/movie.d20.gif

movie.d20.gif

Something significant must have perturbed the tropical Pacific ocean circulation last winter. My guess is the SSW had something to do with it, but that’s just a guess.
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#1380
Phil

Posted 06 July 2018 - 06:25 PM

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And then we have this behemoth upcoming. Duration matters (and this is intraseasonal) but as modeled it would be the strongest ever trade burst to ever occur after 7/1 in a developing niño year west of 150W in the satellite era, unless I’m missing one somewhere.

W3uIwoT.gif
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#1381
Webberweather53

Posted 07 July 2018 - 04:47 AM

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Interesting. I’ll have to check it out. If the EPS is indeed suggesting low frequency EPAC/WHEM coupling, that is definitely a bigger deal than the CFSv2 suggesting it. Because the CFS/GEFS are always trying to throw convection into the WHEM. :lol:

Remember last year how Dr. Paul Roundy (whom I respect immensely) was constantly posting those images of the CFSv2 projecting a flip to westerlies across the eastern and central Pacific? Of course it never happened..fooled me too.

 

Here's what the EPS has in store through most of the rest of July, obviously we have a huge trade wind burst in the upcoming week, but we then have a substantial WWB west of the dateline but intriguingly it doesn't propagate east of the dateline like the last one, the EPS does have a modest wet bias over the Maritime Continent so I wouldn't take these forecasts at face value but it's done a reasonably good job even at this range over the past few months.

ekOOUrQ9.jpg

 

 

 

Here its forecast from over a month ago which correctly sniffed out the MJO skipping the WP even 4 weeks in advance! That's pretty impressive

w5teOGR3.jpg


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#1382
Webberweather53

Posted 07 July 2018 - 04:58 AM

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Here's what the EPS has in store through most of the rest of July, obviously we have a huge trade wind burst in the upcoming week, but we then have a substantial WWB west of the dateline but intriguingly it doesn't propagate east of the dateline like the last one, the EPS does have a modest wet bias over the Maritime Continent so I wouldn't take these forecasts at face value but it's done a reasonably good job even at this range over the past few months.

ekOOUrQ9.jpg

 

 

 

Here its forecast from over a month ago which correctly sniffed out the MJO skipping the WP even 4 weeks in advance! That's pretty impressive

w5teOGR3.jpg

 

 

Here's what the latest 45 day forecast shows, look how the trades are virtually dead in the Atlantic from mid July onward, that would favor a major, prolonged warming in the tropical Atlantic. If this verifies I'll certainly start to have faith in a head fake to warm neutral ENSO, classic late 19th-early 20th century behavior (again)... We also just completely lost whatever +PMM we had going into the summer granted it usually fades after the spring, but this doesn't help my confidence in a weak-moderate NINO this year. Really need the tropical Atlantic to stay cold to keep this solution alive...

 

jimcThLS.jpg


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#1383
Webberweather53

Posted 07 July 2018 - 05:26 AM

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And then we have this behemoth upcoming. Duration matters (and this is intraseasonal) but as modeled it would be the strongest ever trade burst to ever occur after 7/1 in a developing niño year west of 150W in the satellite era, unless I’m missing one somewhere.

W3uIwoT.gif

 

 

Yeah 2009 says hi, the dateline trade wind burst in July was somewhere in the ballpark of 8-10 m/s, pretty close to what's forecasted in the next week or so. It still amazes me that this year found a way to produce a borderline strong El Nino, you wouldn't know that from looking at the U850 evolution. Like this year however 2009 had a huge OKW early in the game to get it thru the summer (this year's was bigger actually) and like w/ most weak-moderate events (although it could be argued 2009-10 was strong), the trades relaxed after the September equinox and that was all she wrote. This pretty remarkable east-central Pacific trade wind burst this late in the game still would not be enough to convince me of a head fake given what happened in 2009-10. It's actually borderline scary how similar the trade wind evolution this July looks to July 2009.

64.118.103.72.187.7.30.33.png


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#1384
Webberweather53

Posted 07 July 2018 - 06:26 AM

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This is actually a pretty bizarre situation...it actually looks like the entire equatorial Pacific overturning cell has been knocked onto its side, creating the fabric of spatial dissonance. I think we’ll need to widen our 5*N/5*S hovmollers to accurately capture this!

The NH wavecycle is clearly way ahead of the SH. Note the westward retraction of the SH subsurface warmth bifurcating from the first OKW (which is already well into the EPAC) recharging that weak OKW in the WPAC, while the NH is just a massive OHC void propagating westward ahead of the initial OKW. So disorganized.

http://www.cpc.ncep....y/movie.d20.gif

movie.d20.gif

Something significant must have perturbed the tropical Pacific ocean circulation last winter. My guess is the SSW had something to do with it, but that’s just a guess.

 

I personally think that's exactly what happened, the SSWE likely set off the MJO pulse in February which then kickstarted the advancement towards NINO-esque conditions this year and likely triggered the first big OKW we saw this past spring.


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#1385
Phil

Posted 07 July 2018 - 08:28 AM

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Here's what the latest 45 day forecast shows, look how the trades are virtually dead in the Atlantic from mid July onward, that would favor a major, prolonged warming in the tropical Atlantic. If this verifies I'll certainly start to have faith in a head fake to warm neutral ENSO, classic late 19th-early 20th century behavior (again)... We also just completely lost whatever +PMM we had going into the summer granted it usually fades after the spring, but this doesn't help my confidence in a weak-moderate NINO this year. Really need the tropical Atlantic to stay cold to keep this solution alive...

jimcThLS.jpg


Interesting information. Does Dr. Maue have that EPS hovmoller plot available for 0-10N, by chance?

I’d be curious to see how far north those westerly anomalies extend across the Atlantic..since the trade wind variations that modulate the AMM seem to focus somewhat north of the equator.
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#1386
Phil

Posted 07 July 2018 - 08:39 AM

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I posted this last night in the western thread, but another factor that might play into the midsummer progression is the completion of this round of poleward +AAM propagation. Does it recycle fast enough? The previous cycle of -AAM propagation certainly affected the tropical forcing through boreal spring.

We were depositing easterly momentum above the zero wind line following the SSW, which along with the transitioning QBO at/below 50mb could have preconditioned the system for this recoiling vacillation.

ZVCSc3d.jpg

I think the evacuation of easterlies from the tropical tropopause could (theoretically) stabilize the Walker Cell, or it could also undercut it and/or bump it eastward and allow for more WWB activity west of the dateline. Hard to know.

Might even depend on the state of subseasonal wave activity! So fascinating.
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#1387
Phil

Posted 07 July 2018 - 08:57 AM

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Yeah 2009 says hi, the dateline trade wind burst in July was somewhere in the ballpark of 8-10 m/s, pretty close to what's forecasted in the next week or so. It still amazes me that this year found a way to produce a borderline strong El Nino, you wouldn't know that from looking at the U850 evolution. Like this year however 2009 had a huge OKW early in the game to get it thru the summer (this year's was bigger actually) and like w/ most weak-moderate events (although it could be argued 2009-10 was strong), the trades relaxed after the September equinox and that was all she wrote. This pretty remarkable east-central Pacific trade wind burst this late in the game still would not be enough to convince me of a head fake given what happened in 2009-10. It's actually borderline scary how similar the trade wind evolution this July looks to July 2009.
64.118.103.72.187.7.30.33.png


Hmm..that one is interesting. Definitely had the WWB activity over the IPWP, but those are some hefty dateline trade bursts as well.

I wonder if, when the QBO is negative @ 50mb, the reduction in off-equator convection during the -PMM can actually aid El Niño development in some circumstances. Would definitely help keep the Pacific ITCZ/Hadley Cell retracted equatorward and stronger/tighter.

Could also explain why 2014 temporarily stepped back despite the favorable early season forcing, and it could also explain why 2009 went “all-in” with little push.

And 2012 had almost zero mechanical support, yet it nearly pulled off a canonical event. I sort of think there’s a bug hidden deep within the climatology that applies specifically to -QBO 50mb cases, as it relates to the PMM and EPAC ITCZ structure. But I’m not sure yet. Could be coincidence or something temporary and confined to recent decades only.
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#1388
Webberweather53

Posted 07 July 2018 - 09:44 AM

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You have a point re: it being difficult to avoid some type of recovery in the AMM following record lows. So I’m not going to try and claim that I was “correct” if the recovery is modest. ;) Obviously I’m expecting something bigger, more similar to what happened in 1989. If I’m wrong I’ll be the first one to admit it.

And yeah, it would be interestino to repeat the “slow walk” to El Niño again, after it just happened in 2014. Might be time to consider the effects of low solar on ENSO tendencies (paleo data unanimously indicates that more frequent niños and +PDO/ weak Asian monsoons are the typical climatological responses to minimums in solar activity).

I’ve taken a deeper look into this and I am somewhat convinced the North African monsoon has a lot to do with the recent and projected slackening of the east-central Atlantic trades, we’ve observed a long term trend since the 1970s towards a wetter Africa and this year is continuing that trend. Large-scale convergence into North Africa usually means there’s anomalous westerly flow over the tropical Atlantic which shuts down the stronger easterlies we’ve observed in and immediately after winters dominated by a +NAO due in part to AGW, long term trend towards more E hem forcing, and the preceding winter ENSO (Niña)

#1389
Phil

Posted 07 July 2018 - 10:06 AM

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I’ve taken a deeper look into this and I am somewhat convinced the North African monsoon has a lot to do with the recent and projected slackening of the east-central Atlantic trades, we’ve observed a long term trend since the 1970s towards a wetter Africa and this year is continuing that trend. Large-scale convergence into North Africa usually means there’s anomalous westerly flow over the tropical Atlantic which shuts down the stronger easterlies we’ve observed in and immediately after winters dominated by a +NAO due in part to AGW, long term trend towards more E hem forcing, and the preceding winter ENSO (Niña)


Interesting take. The presence of this +IOD cell would also lend support to the African monsoon, so you might be onto something.
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#1390
Phil

Posted 07 July 2018 - 11:21 AM

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FWIW, there are indications that the -AMO type SSTA signature has been decreasing in frequency during the summer through most of the Holocene, thanks to a strengthening LTG under declining obliquity.

It so happens that this is the inverse of our (ongoing) shorter term climate state (weaker LTG/+NAO/warm globe).

Zr9bu1x.jpg
Zr9bu1x.jpg

Which makes sense if warm periods bias towards +NAO/poleward jets during the cold season.

u7mSckF.jpg

So the increased seasonality of the AMM is something pretty typical of warm periods. Note the early/mid Holocene behavior w/ the weaker insolation gradient (analogous to periods of weaker LTG for other reasons).

VpUCK3G.jpg

And the long term effects of the strengthening LTG through the Holocene also fits the structure for cold climate periods w/ the increased ENSO frequency and weaker Asian monsoons/smaller IPWP.

kYCUgjQ.jpg
f8T7yvl.jpg

Note the transition out of the MWP/into the LIA featured a matching tendency.

keyah9F.jpg
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Warm Season 2018
90+ degree days: 5
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Severe Days: 1
Total rainfall: 1.77”
Highest Gust: 54mph
Warmest High: 94.6*F
Warmest low: 65.5*F

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#1391
Phil

Posted 10 July 2018 - 08:42 AM

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Shoot, this was supposed to be the second image.

DkZDrCc.jpg
Personal Weather Station, Live Stream on Wunderground: https://www.wundergr...BETHE62#history

Warm Season 2018
90+ degree days: 5
Thunderstorm Days: 5
Severe Days: 1
Total rainfall: 1.77”
Highest Gust: 54mph
Warmest High: 94.6*F
Warmest low: 65.5*F

Live Weather Stream

#1392
Phil

Posted 10 July 2018 - 08:59 AM

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Mike Ventrice is going all-in on the ECMWF monthly depiction of an El Niño standing wave developing after this MJO passage.

Color me skeptical. For now.
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Personal Weather Station, Live Stream on Wunderground: https://www.wundergr...BETHE62#history

Warm Season 2018
90+ degree days: 5
Thunderstorm Days: 5
Severe Days: 1
Total rainfall: 1.77”
Highest Gust: 54mph
Warmest High: 94.6*F
Warmest low: 65.5*F

Live Weather Stream

#1393
Phil

Posted 13 July 2018 - 05:01 PM

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The ongoing trade surge has taken a big bite out of the WPAC/Dateline SSTs.

This is one of the reasons I avoid relying too much on seasonal/climate modeling of tropical forcing (especially regarding low frequency transitions). They have a rough time simulating this type of air/sea interactivity on the intraseasonal scale. They don’t “see” it. All parameterized.

fdzFFnO.gif
Personal Weather Station, Live Stream on Wunderground: https://www.wundergr...BETHE62#history

Warm Season 2018
90+ degree days: 5
Thunderstorm Days: 5
Severe Days: 1
Total rainfall: 1.77”
Highest Gust: 54mph
Warmest High: 94.6*F
Warmest low: 65.5*F

Live Weather Stream

#1394
weatherfan2012

Posted 13 July 2018 - 06:21 PM

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The ongoing trade surge has taken a big bite out of the WPAC/Dateline SSTs.
This is one of the reasons I avoid relying too much on seasonal/climate modeling of tropical forcing (especially regarding low frequency transitions). They have a rough time simulating this type of air/sea interactivity on the intraseasonal scale. They don’t “see” it. All parameterized.fdzFFnO.gif

The ongoing trade surge has taken a big bite out of the WPAC/Dateline SSTs.
This is one of the reasons I avoid relying too much on seasonal/climate modeling of tropical forcing (especially regarding low frequency transitions). They have a rough time simulating this type of air/sea interactivity on the intraseasonal scale. They don’t “see” it. All parameterized.fdzFFnO.gif

yeah I don't get the moderate El Nino talk from many this year This has a warm neuturl feel to it El Nino most likey holds off until spring summer 2019.