February Weather in the Pacific Northwest

[Poulsbo Snowman]

Most of this falls around day 9.

At least it's not day 10.

[Gradient Keeper]

Timing moved ahead a bit on 12z GEM, ECMWF Op. That was nice. 12z EPS a notch better. 12z CMCE looks good. We need to see timing move inside Day 6-7 with arctic air moving down into northern Washington or Columbia Basin. Then it becomes more believable.

 

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00z GFS in 6 hours 50 minutes

[snow_wizard]

FWIW this is the first time with this potential event that the CFS has picked up on a potential prolonged period of chilly weather.  Up until now it showed a brief cool period and then rapidly warmed it up.  The latest runs show it staying below normal for the next two weeks.  It's kind of interesting this model has been somewhat useful in forecasting cold in the short range.  It ignored all of the false alarms that we have seen with the other models earlier in the year.  This is only true out to day 20 or so.

[snow_wizard]

Maybe if we are lucky we will see the GOA ridge dominate right through spring and even into summer now.  It was sorely missed in January.

[TigerWoodsLibido]

Most of this falls around day 9.

Can someone post the Oregon map pls?

[Gradient Keeper]

Maybe if we are lucky we will see the GOA ridge dominate right through spring and even into summer now.  It was sorely missed in January.

I hope so. Snow in July would be terrific.

 

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00z GEM in 6 hours 54 minutes

[Deweydog]

47 at PDX at 1pm on 2-10 with full sunshine.

[Frontal Snowsquall]

The new 12z EURO looks great at day 10. Arctic air has already made its way into the PNW from Canada and is poised to encompass the whole region. Good positive tilt to the Arctic trough will deliver the goods. There's a truckload of frigid air ready to get tapped into.

 

http://maps1.pivotalweather.com/maps/models/ecmwf/2018021012/240/500h_anom.na.png

http://maps1.pivotalweather.com/maps/models/ecmwf/2018021012/240/850t.na.png

[tomas]

                                      
  

[snow_wizard]

The new 12z EURO looks great at day 10. Arctic air has already made its way into the PNW from Canada and is poised to encompass the whole region. Good positive tilt to the Arctic trough will deliver the goods. There's a truckload of frigid air ready to get tapped into.

 

 

That is certainly a classic snow setup with the jet looping out over the ocean.

[tomas]

                                                                                              http://wxmaps.org/pix/avnmr1.24hr.png
 

[snow_wizard]

The NWS forecast is a bit odd.  Highs near 50 all next week with a series of cold troughs dropping down from the north?

[TT-SEA]

The NWS forecast is a bit odd. Highs near 50 all next week with a series of cold troughs dropping down from the north?

 

Do not worry about what the NWS says. Completely irrelevant.

[seattleweatherguy]

Nws always conservative

[HighlandExperience]

The NWS forecast is a bit odd. Highs near 50 all next week with a series of cold troughs dropping down from the north?

Probably just jaded

[Front Ranger]

The mid 1950s was just an insanely cold period throughout. Every season of those years was cold.

And then 1958 happened.

[Phil]

Keep in mind the trends thru most of this winter. Strong Greenland vortex = PNW failure via wave dispersion.

 

That Greenland vortex will (finally!) die a slow, painful death over the next few weeks, as the PV sustaining it aloft is ripped to shreds. However, until it does, you guys are probably out of luck. I know some of you might disagree or hate me for saying this, but when you analyze the physics of it, there’s no denying it.

 

Some winters can deliver even with an ugly, baratropic mode Greenland vortex. However, the way the boundary conditions are stacked *this year*, it can’t happen unless the vortex is removed from the picture.

[SilverFallsAndrew]

Okay little trough there on the 18z.

[seattleweatherguy]

Keep in mind the trends thru most of this winter. Strong Greenland vortex = PNW failure via wave dispersion.

 

That Greenland vortex will (finally!) die a slow, painful death over the next few weeks, as the PV sustaining it aloft is ripped to shreds. However, until it does, you guys are probably out of luck. I know some of you might disagree or hate me for saying this, but when you analyze the physics of it, there’s no denying it.

 

Some winters can deliver even with an ugly, baratropic mode Greenland vortex. However, the way the boundary conditions are stacked *this year*, it can’t happen unless the vortex is removed from the picture.

Therefore no event in 10 days?

[Gradient Keeper]

18z GFS making moves towards GFS/GEM.

 

Animated GIF of past 4 GFS runs centered at 10 AM Sunday. Nice trend. https://imgur.com/Ep4IDAV

[Gradient Keeper]

Day 9 not bad. Now let's see if we have ensemble support and go from there. Onto 00z

[MossMan]

Therefore no event in 10 days?

Nope, better sharpen the blades and change the oil in your mower, you will be doing yard work in 10 days according to Phil!

[Deweydog]

It's our year!!!!

[seattleweatherguy]

Nope, better sharpen the blades and change the oil in your mower, you will be doing yard work in 10 days according to Phil!

I'm already doing yard work

[Farmboy]

Keep in mind the trends thru most of this winter. Strong Greenland vortex = PNW failure via wave dispersion.

 

That Greenland vortex will (finally!) die a slow, painful death over the next few weeks, as the PV sustaining it aloft is ripped to shreds. However, until it does, you guys are probably out of luck. I know some of you might disagree or hate me for saying this, but when you analyze the physics of it, there’s no denying it.

 

Some winters can deliver even with an ugly, baratropic mode Greenland vortex. However, the way the boundary conditions are stacked *this year*, it can’t happen unless the vortex is removed from the picture.

So you're saying models showing cold 9-10 days from now are garbage runs that we should ignore?

[Phil]

Therefore no event in 10 days?

No, I’m not saying that at all.

 

I’m saying it will probably take longer than is currently modeled, given the TPV filament isn’t sufficiently emasculated until d7/d8. Unless things speed up aloft, which is certainly possible.

[Front Ranger]

18z GFS making moves towards GFS/GEM.

 

Animated GIF of past 4 GFS runs centered at 10 AM Sunday. Nice trend. https://imgur.com/Ep4IDAV

 

Yeah, definite improvement. Within 7 days, too.

[Phil]

So you're saying models showing cold 9-10 days from now are garbage runs that we should ignore?

No. FWIW, the 18z GFS solution is plausible early on (verbatim) because it elongates the TPV quickly and continues the wave-2 WAFz forcing mode thereafter.

 

In regards to that, I think the ECMWF solution is mostly horsecrap, probably just it’s usual bias of digging troughs too far southwest over terrain in zonal regimes. The GGEM also over-plays retrogressions, in a similar manner.

[Phil]

[snow_wizard]

Okay little trough there on the 18z.

 

It actually gets respectably cold around day 9.  The big difference between the GFS and the other models is it never makes the block as massive as the GEM and ECMWF do.  That difference has even shown up on the respective ensemble means.  GFS and it's ensemble are the outlier right now.  Let's hope the more massive block verifies.

[snow_wizard]

Keep in mind the trends thru most of this winter. Strong Greenland vortex = PNW failure via wave dispersion.

 

That Greenland vortex will (finally!) die a slow, painful death over the next few weeks, as the PV sustaining it aloft is ripped to shreds. However, until it does, you guys are probably out of luck. I know some of you might disagree or hate me for saying this, but when you analyze the physics of it, there’s no denying it.

 

Some winters can deliver even with an ugly, baratropic mode Greenland vortex. However, the way the boundary conditions are stacked *this year*, it can’t happen unless the vortex is removed from the picture.

 

I'm becoming increasingly convinced the whole +NAO thing being good for the West is indeed horse .

 

The SSW should help us out with the coming pattern evolution.

[Phil]

[Phil]

I'm becoming increasingly convinced the whole +NAO thing being good for the West is indeed horse s**t.

 

The SSW should help us out with the coming pattern evolution.

Exactly.

 

I also used to think +NAO helped (or was a non-factor) for PNW winters. However, as I’ve learned more about weather and climate dynamics over the years, the more I’ve realized that the NAO and PNA are literally a single, long-period wavetrain.

 

The low frequency asymmetric forcing states require that the NAO/PNA be coupled in the long term. Check out the PNA/NAO correlation since 1950 (below).

 

There’s absolutely NO DOUBT that a +NAO represents a detrimental state for the PNW winters, through a direct exchange with the PNA. Again, two parts of a single asymmetric forcing machine.

 

[Front Ranger]

I'm becoming increasingly convinced the whole +NAO thing being good for the West is indeed horse s**t.

 

The long term evidence is +NAO in and of itself is neither good or bad for the West. It depends on other large scale pattern factors. Sometimes the NAO/PNA are coupled as Phil is arguing, but at other times they are not. There have been plenty of examples given of times in the past when the PNW/West scored with a +NAO, and plenty of times we've scored with -NAO.

 

And there are different types of +NAO/-NAO. More important is how the high latitude blocking is configured across the northern hemisphere.

[Front Ranger]

Exactly.

 

I also used to think +NAO helped (or was a non-factor) for PNW winters. However, as I’ve learned more about weather and climate dynamics over the years, the more I’ve realized that the NAO and PNA are literally a single, long-period wavetrain.

 

The low frequency asymmetric forcing states require that the NAO/PNA be coupled in the long term. Check out the PNA/NAO correlation since 1950 (below).

 

There’s absolutely NO DOUBT that a +NAO represents a detrimental state for the PNW winters, through a direct exchange with the PNA. Again, two parts of a single asymmetric forcing machine.

 

 

I think the main takeaway from that graph is the trend towards less blocking since 1980. In both the PNA and NAO regions.

[Phil]

On the short term/yearly scale, the PNA/NAO can diverge via symmetric conduits (ENSO/QBO, etc).

 

Long term, however, asymmetric responses are dominant, and these are responsible for the long term changes to PNW climate (and global climate), including the trend to positive annular modes (+AO/+AAO, weaker BDC/chemical fluxes), the weakening and broadening of the tropospheric z-cell network, poleward shift in the jet streams, the weakening of tropical wind speeds and convection, the associated cloud cover decrease between 30N-30S, and the associated global heat uptake.

[Gradient Keeper]

18z GEFS says NOPE

 

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00z ECMWF in 6 hours 4 minutes

[Phil]

I think the main takeaway from that graph is the trend towards less blocking since 1980. In both the PNA and NAO regions.

Interesting tidbit here. Before this winter, the most persistently +NAO (DJF) on record was 2014/15. It looks like we could break that record this year. It’ll be close, but the fact we could even come close is astounding to me.

 

The good news, though, is that we’ll be diverging from 2015 (et al) in a significant way this spring/summer. At long last, the foundation of the 2013-2017 +PDO/+PNA is being compromised, as the huge WPAC heat bomb begins to shrink, and NE portion of the warm pool begins evacuating poleward (classic -PDO precursor).

[Phil]

And there are different types of +NAO/-NAO. More important is how the high latitude blocking is configured across the northern hemisphere.

I agree with this part. And you make a good point regarding the (shorter term) divergence between the PNA/NAO, which can certainly happen.

 

I’m speaking more long term, since the whole “climate deterioration” thing is often talked about here.

 

You look at the PNW climate of the 19th century, and compare it the climate of today, and it quickly becomes obvious that the 2*F rise in global temperature (less over the NPAC) cannot explain such a dramatic swing in temperature/snowfall. Not by itself. You need a significant change to the circulation and storm track. That’s where the long term, asymmetric wavetrain responses come into play.

[Phil]

This is amazing. Look how different the circulation was during the late 19th/early 20th century, towards the end of the LIA.

 

All of these 5-year blocks were west-based -NAO, and none of them have Hudson Bay vortexes.

 

1875-1880:

 

 

 

1885-1890:

 

 

1890-1895:

 

 

 

1895-1900:

 

 

 

1900-1905: