November 2017 PNW Discussion Thread

[Brian_in_Leavenworth]

That's the 2m temperature anomaly (mean of all 51 ensemble members) through the first four weeks of the run. I just posted snapshots of the control run.

So is the control run colder for the PNW than the ensemble mean, or am I reading your original post wrong and the low 500mb heights just means a lot of storms but normal temps? If it did show cold temps for us, it is different than the ensembles, so probably the ensembles would be more accurate? Not sure how the really long range models work.

[Geos]

Next 10 days plenty of rain and mountain snow.

 

 

[Phil]

So is the control run colder for the PNW than the ensemble mean, or am I reading your original post wrong and the low 500mb heights just means a lot of storms but normal temps? If it did show cold temps for us, it is different than the ensembles, so probably the ensembles would be more accurate? Not sure how the really long range models work.

The control run is colder for the PNW, but I mostly posted it for laughs. Probably won't be that extreme, as far as the blocking is concerned.

[ShawniganLake]

Frozen Turkeys?

[stuffradio]

Frozen Turkeys?

GFS doesn't go that far yet, but they will be frozen up here the week before.

[Timmy]

I'm not sure. My hunch is that January will be the coldest month relative to average in the PNW, but these blocking patterns can be tricky to forecast (as far as specifics are concerned).

how much snow at my house?

[ShawniganLake]

GFS doesn't go that far yet, but they will be frozen up here the week before.

It goes to the eve of thanksgiving.

[Phil]

how much snow at my house?

No precipitation anywhere except Tim's house. Sorry, man.

[Phil]

00z GFS flips the system state too.

 

Days 1-5 vs days 11-16:

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/8FC2CAA2-E421-420A-9FFC-3DCAAE0ABBF5_zpsiqzze07r.png

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/41A3435B-BA4E-4B0A-B5B8-11C0CA386AB9_zpsl6mjmg6s.png

[Phil]

We lose at least 0.7C off the NH temperature anomaly as a result of the NAO flip.

 

Days 1-5:

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/449EFBCD-57CA-40F5-B0EA-5AD48733DE40_zps1q9wjwax.png

 

Days 11-16:

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/386A0CC2-1D75-4185-9130-22A1A08C86F0_zpsmykdeaso.png

[snow_wizard]

00z GFS flips the system state too.

 

Days 1-5 vs days 11-16:

 

 

 

Love that negative NAO!  Given the overall blockiness being shown over the next two weeks a good outcome is hardly far fetched.

[Phil]

Love that negative NAO! Given the overall blockiness being shown over the next two weeks a good outcome is hardly far fetched.

Yeah, this might be the big year you've been waiting for.

 

I don't want to say too much and jinx it, though. Still, some of these cell configurations are throwbacks to the good 'ole days, so we're definitely heading in the right direction, from a large scale standpoint.

[Jesse]

So is that ridiculous looking high latitude blocking pattern just model porn at this point, or are there factors actually pointing to possible verification?

[Phil]

So is that ridiculous looking high latitude blocking pattern just model porn at this point, or are there factors actually pointing to possible verification?

It's more than model porn. Posted about this earlier tonight (and I think we discussed it in mid/late October).

 

Regarding the poleward propagating -AAM anomaly.

 

Mentioned this a few times already, but here's that slow poleward propagating -AAM anomaly. Pretty much a classic precursor to a poleward amplification of the surf zone/high latitude blocking.http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/FCB48B79-5D94-49F5-861F-C7F0D65DA334_zps8jxn46j8.jpg

Might be a bit overdone on some guidance, but given the preconditioning of the system state right now, we're almost certainly trending into a negative north annular mode (-AO) and a continuation of the -PNA starting around Thanksgiving and likely continuing into December.

 

Given the aforementioned -PNA/-ENSO background state, cold air is favored to be available/directed into western North America in the long run.

[Jesse]

It's more than model porn. Posted about this earlier tonight (and I think we discussed it in mid/late October).

 

Regarding the poleward propagating -AAM anomaly.

 

Might be a bit overdone, but given the preconditioning of the system state right now, we're almost certainly trending into a negative north annular mode (-AO) starting around Thanksgiving and likely continuing into December.

 

We also have a -PNA/-ENSO background state ongoing so this will favor cold being available/directed into western North America in the long run.

Great info. I must have missed it. Been plugging away at a lab write up the last several hours.

[snow_wizard]

Another interesting note is the sun has been spotless for a good part of the past month and the AP index is VERY low now.  Low solar will be our friend this winter.

[snow_wizard]

Yeah, this might be the big year you've been waiting for.

 

I don't want to say too much and jinx it, though. Still, some of these cell configurations are throwbacks to the good 'ole days, so we're definitely heading in the right direction, from a large scale standpoint.

 

Looks like we may be arriving at almost the same place using different methods again.  I've been watching these intense / relentless high pressure anoms over the NE Pacific.  Past history says we are in VERY good company.  Some of our coldest and blockiest seasons on record.

[Phil]

Another interesting note is the sun has been spotless for a good part of the past month and the AP index is VERY low now. Low solar will be our friend this winter.

The AP Index definitely dropped relative to September. Would still like to see it drop further this month, though.

 

http://services.swpc.noaa.gov/images/solar-cycle-planetary-a-index.gif

[Phil]

Looks like we may be arriving at almost the same place using different methods again. I've been watching these intense / relentless high pressure anoms over the NE Pacific. Past history says we are in VERY good company. Some of our coldest and blockiest seasons on record.

Yeah, usually a good sign when different methodologies give you the similar results.

 

I'm not saying I think this will necessarily be a 1949-50 repeat, but the potential for a very big winter appears to be present at this time, in my opinion. At least for your region.

[Phil]

Great info. I must have missed it. Been plugging away at a lab write up the last several hours.

Thanks man. Sounds like a pain in the brain..don't blow a fuse!

[stuffradio]

It goes to the eve of thanksgiving.

HAHA WHoops I thought for some reason it was the last week of November. My bad.

[MossMan]

Currently 29 degrees here.

[stuffradio]

There's a member tanking to -15C here.

 

 

AAM forecasting to tank around then

 

 

NAO forecast to go negative around the 18th.

[snow_wizard]

The AP Index definitely dropped relative to September. Would still like to see it drop further this month, though.

 

 

Indeed.  I was referring to the daily readings.  The last one was around 1.

[snow_wizard]

This composite of the big 3 troughs we have had over the past 6 weeks is absolutely insane.  You would be hard pressed to find another late September - early November period that had anything similar.  This captures a 3 day average from each trough.

 

 

[HighlandExperience]

This composite of the big 3 troughs we have had over the past 6 weeks is absolutely insane. You would be hard pressed to find another late September - early November period that had anything similar. This captures a 3 day average from each trough.

We need that in December and January

[TT-SEA]

40 at SEA and 38 here this morning.

 

Could be a long wait now for a hard freeze... which is interesting from a garden perspective here.  

[SilverFallsAndrew]

Salem hit 30 last night

[SilverFallsAndrew]

Ended up hitting freezing around 9pm last night, so picked up 2 freeze days in one night.

[TT-SEA]

Spectacular sunrise... and snow does not melt at 37 when the dewpoint is 22. 

 

[Kayla]

North American snowcover is pretty high right now.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/4A403051-1A0C-4F1D-BC02-F91ABD1FD7CE_zpssy3upewp.jpg

 

Yeah...and most of it is in Montana! Pretty incredible to see basically the entire state with significant snow cover this early in the season.

 

[MossMan]

Currently 29 with everything covered in frost here.

[Phil]

Impressive sea/ice surface temperatures for so early in the season..

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/D14CCF75-42BD-4C11-B117-4673A1EF4856_zps4xjg8rjs.png

[Phil]

Snow depth is above average across most of the NH. Should have no problem developing a cold core of Arctic air this winter.

 

[WeatherMan101]

Another update for us in Vancouver, Canada

 

 

Statements

4:26 AM PST Tuesday 07 November 2017

Special weather statement in effect for:

 

City of Vancouver - including Burnaby and New Westminster

Metro Vancouver - northeast including Coquitlam and Maple Ridge

Metro Vancouver - southeast including Surrey and Langley

Metro Vancouver - southwest including Richmond and Delta

North Shore - including West Vancouver and North Vancouver

A mix of rain and snow on the way...

 

A slow-moving cold front will approach the South Coast Tuesday night. As it nears, outflow winds will intensify through the Fraser Valley and Howe Sound. Bands of moisture will also accompany the front and with cold air in place, many areas could see snow or mixed rain and snow.

 

Current forecasts indicate that a weak band of precipitation will arrive over the South Coast early Wednesday morning followed by a more intense band later Wednesday afternoon or evening.

 

There remains considerable uncertainty regarding the timing of the precipitation and the likelihood of snow. During the day Wednesday, little to no accumulation is expected. On Wednesday night, the most likely areas to see small snowfall accumulations are the inland areas exposed to outflow winds and possibly higher elevations.

[WeatherMan101]

Spectacular sunrise... and snow does not melt at 37 when the dewpoint is 22.

 

Great picture!

[Jesse]

Strong winds kept temperatures in the upper 30s here this morning, but my first freeze was a week ago anyway.

 

The sunrise was spectacular, btw.

[Phil]

In other interesting news, the Antarctic O^3 "hole" has shrunk to its lowest level since 1988, after reaching record levels back in 2015. Is this just a blip, thanks to BDC recoil following the double +QBO (poleward propagation of tightened subtropical O^3 belts as TW's reverse)? Or are we finally be witnessing the demise of the increasingly potent +SAM (which has been trending positive for centuries)? Time will tell..my guess is it's mostly the former but it would be great if it were the latter.

 

Believe it or not, the SAM relationship to the tropical WPAC is very strong on decadal timescales. A -SAM pressure gradient really helps knock down the warm pool through increased equatorward deepwater subsurface fluxes. Takes decades but it's very evident in the paleo data.

[FroYoBro]

In other interesting news, the Antarctic O^3 "hole" has shrunk to its lowest level since 1988, after reaching record levels back in 2015. Is this just a blip, thanks to BDC recoil following the double +QBO (poleward propagation of tightened subtropical O^3 belts as TW's reverse)? Or are we finally be witnessing the demise of the increasingly potent +SAM (which has been trending positive for centuries)? Time will tell..my guess is it's mostly the former but it would be great if it were the latter.

 

Believe it or not, the SAM relationship to the tropical WPAC is very strong on decadal timescales. A -SAM pressure gradient really helps knock down the warm pool through increased equatorward deepwater subsurface fluxes. Takes decades but it's very evident in the paleo data.

 

Almost assuredly. 

[Timmy Supercell]

Looks like a low of 21 degrees this morning.