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Central US 2014-15 Winter Preseason Discussion


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12z model run teleconnections: Euro now has the -AO in a steady fall until it reaches about -5 right before the end of the run. The -EPO goes off the chart at -6+. The 'old' GFS isn't as extreme with the -AO... It has it settling around -3 or so. The -EPO is similar to the Euro. Negative AO and EPO is cold cold cold.

 

The main difference between the Euro/GFS seems to be with the PNA (this is the western troughing/ridging). The GFS has the +PNA falling to around neutral by the 10th and then it rises to around +2 by the 16th. The Euro is different in that it has a similar fall to around neutral by the 10th, however it has more of an up/down pattern after that and it is under +1 by the 16th and continuing to fall after that.

 

A positive PNA features more ridging in the west while a negative PNA features more troughing. 

 

This makes sense considering the 12z Euro has a storm system developing in SW Canada and NW US at the end of the run, and a system out in the ocean west of California.

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the 12Z parallel GFS suggests a 1050mb Arctic high settling into E WY, NW NE, NE CO on Thursday. Very impressive for mid November.

Yep...some of the numerical output for Wed 11/12 is shocking.  

 

Unless I'm misreading it, MOS for Casper WY shows 2/-21 that day.  The normal high/low is 47/23...which means a -45 departure.  Not saying MOS will verify...but wow.

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Heh...Southern Plains storm signal and a Coastal developing in the NW Gulf in the medium to longer range.

11092014 12Z Euro 192 ecmwf_z500a_namer_9.png

11092014 12Z Euro 192 ecmwf_T850a_namer_9.png

Looks awesome. Think things may get a little crazier than currently anticipated? All I can say is bring it on.

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Truly an amazing pattern developing in the medium to longer range. The Omega Block is most impressive and with a potential  -4+ AO/-4+ EPO/+4.5 or greater PNA suggested by the guidance, the storm signal being depicted by the European scheme may not be that far fetched regarding a Winter like storm developing next weekend across portions of the Southern Rockies/Southern Plains. The fly in the ointment continues to be the data assimilation of the strong shortwave over the Pacific undercutting the PNA Ridge and dropping SE into the Great Basin and traversing E. The GFS is showing its typical bias for being too progressive in handling this feature and therefore suggests a less amped up or drier solution while the Euro keeps this disturbance more intact and attempts to wrap it up over New Mexico. A robust cckw  over the Pacific as well as a favorable MJO to me suggests the Euro may be doing a better job handling this feature which could have a significant impact on the sensible weather we may see next weekend. With the potential of a NW Gulf Coastal low/trough developing, it will be interesting to watch as the work week unfolds.

 

sat_wv_west_loop-12.gif

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Now if this turns into a Modoki like Joe D'Aleo has been forecasting for months and months, that would further enhance our chances for a good winter.

 

You can see some cooler waters trying to surface in the eastern regions. Assuming they surface, this would be the Modoki.

 

wkxzteq_anm.gif

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The weekend forecast is still somewhat murky other than a Coastal Low/trough developing along the Middle Texas Coast Saturday afternoon and moving NE toward Louisiana on Sunday. A quick return flow off the Gulf sets up as a fast moving shortwave/trough swings in from the SW into the Southern Rockies. This disturbance is currently S of the Alsatians and I'd like to see a bit more data as well as it enters the RAOB network  The Euro continues to be a bit stronger with this upper air feature increasing lift, but I am a bit skeptical of the boundary layers suggested by the P GFS. It will be interesting as I have mentioned to see how well the upgrade will compare with the Euro in the day 5 range. That said I believe the best shot of wintry weather will be across the higher terrain of New Mexico and possibly in a narrow stripe across the Panhandles of TX/OK, Southern KS into NW AR and MO. Further S if the dry layer can saturate enough, perhaps the a light wintry mix could develop. We will see.

 

 

 

sat_wv_hem_loop-12.gif

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This weekend will be the first big test for the PGFS. It is showing widespread frozen precip (seems to be snow) across the north half of Texas and areas to the north on Sunday into Sunday night.

I hope it's right. The old GFS seems to be getting on board finally as well. Looking more promising at least to see them agree a little better.

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Truly an amazing pattern developing in the medium to longer range. The Omega Block is most impressive and with a potential  -4+ AO/-4+ EPO/+4.5 or greater PNA suggested by the guidance,

Srain, do you think that the ex-Nuri superstorm helped pump up the ridge over Alaska/Arctic Circle, therefore helping the development of the cold vortex over Canada? Would this pattern have developed if there had been only 980mb over the Bering (with closer to normal 500mb heights there?)

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Srain, do you think that the ex-Nuri superstorm helped pump up the ridge over Alaska/Arctic Circle, therefore helping the development of the cold vortex over Canada? Would this pattern have developed if there had been only 980mb over the Bering (with closer to normal 500mb heights there?)

Clearly it did and the WPC/HPC made mention of just how much 'Nuri' changed the entire pattern in their extended update this morning...

 

...UNCERTAINTY ASSESSMENT...

SEVERAL REGIONS OF THE COUNTRY WILL BE A TEMPERATURE AND P-TYPE

CHALLENGE AS THE SHEETS OF LOW-LEVEL ARCTIC AIR SPREAD ACROSS THE

LOWER 48 AND UPPER-LEVEL FLOW IN THE WEST 'DE-AMPLIFIES' THROUGH

TIME. THE DE-AMPLIFICATION PROCESS OCCURRING OUT WEST CREATES A

'TANDEM' TRANSITIONAL FLOW DOWNSTREAM ACROSS THE SOUTHEAST AND

EAST CENTRAL STATES...AS THE UPPER-LEVEL TROUGH OVER SOUTHEAST

CANADA SLOWLY LIFTS NORTHEASTWARD.

STARTING IN THE WEST...THOUGHT THE ENERGY WHICH UNDERCUTS THE

RIDGE IN THE PACIFIC NORTHWEST DAY 4-6 AND BEYOND---IS MORE A

BY-PRODUCT OF THE LOW-LEVEL FLOW TRAJECTORIES ALONG THE WEST COAST

RATHER THAN A TOTAL COLLAPSE OF THE UPPER-LEVEL RIDGE AXIS BETWEEN

45N-50N ALONG 120W-125W. THE EFFECTS OF THE DEEP BERING SEA

CYCLONE (REMNANTS OF 'NURI' CANNOT BE UNDERSTATED) AND HAVE

TOTALLY DISPLACED THE LOW-LEVEL THERMAL PROFILES IN THIS REGION OF

THE WESTERN HEMISPHERE . IN THAT---THE H85-H7 TEMPERATURE REGIME

OVER INTERIOR ALASKA VERSUS THE SOUTHERN CANADIAN AND NORTHERN

ROCKIES ARE ESSENTIALLY REVERSED---WITH ROUGHLY A M18C AIRMASS

OVER MONTANA AND A +6C AIRMASS IN SOUTHEAST ALASKA AT MID-FORECAST

PERIOD! WHAT DOES LOOK A TAD DIFFERENT MID-PERIOD FROM THE

PROJECTED PATTERN AND SOLUTION FIVE DAYS AGO (NOV 6TH CYCLES) IS

HOW DISPLACED THE AIRMASS HAS BECOME OVER ALASKA'S ARCTIC CIRCLE.

MUCH OLDER RUNS AND MOMENTUM FROM 'NURI' AND ITS TROPICAL

INTRUSION HAVE MADE MORE OF A NORTHWARD RATHER THAN EASTWARD

ADJUSTMENT WITH THE MIGRATION OF TROPICAL MOISTURE INTO THE HIGH

LATITUDE AND SLOWED THE OUTCOME OF TROUGHING IN THE GULF OF

ALASKA. 

 

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The JMA Seasonal is out. Not looking too good. Has a +AO look to Dec/Jan but then brings the blocking in for Feb.

http://ds.data.jma.go.jp/tcc/tcc/products/model/probfcst/4mE/fcst/fcst_gl.php

I don't think the Aleutian low is too far east to cause issues... hmm.

http://ds.data.jma.go.jp/tcc/tcc/products/model/

I'm not saying it won't happen but that forecast just looks very unlikely. It does shift the cold air over the west though, which if you look at a temperature map, you can pretty well see where the coldest air is centered right now anyway. I think we'll be persistently cool this winter with brief warm ups. Most of the coldest air right over the spine of the Rockies to the central and southern plains. I haven't really changed my mind much over the last month.

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