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Winter 2020-21 Discussion


CAPE
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9 minutes ago, snowman19 said:

Wouldn’t it be totally unprecedented for the +QBO not to continue to downwell into the bottom of the stratosphere? As far as I know, every positive and negative event on record has downwelled into the lower stratosphere

QBO phase influences the strength of the SPV. The impacts it has on the stratosphere  do not necessarily couple down to the  troposphere.

The TPV and SPV are distinctly separate entities.

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2 hours ago, snowman19 said:

Wouldn’t it be totally unprecedented for the +QBO not to continue to downwell into the bottom of the stratosphere? As far as I know, every positive and negative event on record has downwelled into the lower stratosphere

Usually they do down well, but the timing can be a bit variable and the QBO as a whole has been a little funky the last 4 years for whatever reason (climate or other). 

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6 minutes ago, WxUSAF said:

Yeah, GEFS surface temps are warm for December but the 500mb pattern looks halfway decent for most of it? 

Pretty decent fwiw. I tend to take a peak at the week beyond D15, just to see how things look. All low skill at that range ofc.

Latest Euro weeklies are meh, at least from what I can glean from the really bad h5 graphics on the freebie site. Probably similar enough to the GEFS for the first week or so of Dec, but has at least some weak ridging in the east.

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39 minutes ago, CAPE said:

Pretty decent fwiw. I tend to take a peak at the week beyond D15, just to see how things look. All low skill at that range ofc.

Latest Euro weeklies are meh, at least from what I can glean from the really bad h5 graphics on the freebie site. Probably similar enough to the GEFS for the first week or so of Dec, but has at least some weak ridging in the east.

The Scandinavian-Greenland ridge pattern this fall and progged going forward is nice. Maybe we can hope for some occasional NAO help? If we can couple it with transient Pac ridging we could get some windows.

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3 hours ago, CAPE said:

QBO phase influences the strength of the SPV. The impacts it has on the stratosphere  do not necessarily couple down to the  troposphere.

The TPV and SPV are distinctly separate entities.

NAM state still looks uneventful.

Meanwhile

 

Today's 46-day ECMWF shows a +4-5°C anomaly for the full month of December in the north-central USA (vs 20-year climatology). At face value that would rival the warmest Decembers on record in Minnesota, such as 2015 and 1997 - both super El Niño winters
 
 
 
Image
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2 hours ago, frd said:

NAM state still looks uneventful.

Meanwhile

 

Today's 46-day ECMWF shows a +4-5°C anomaly for the full month of December in the north-central USA (vs 20-year climatology). At face value that would rival the warmest Decembers on record in Minnesota, such as 2015 and 1997 - both super El Niño winters
 
 
 
Image

That is one impressively large area of "warm" 2m temp anomalies. Not sure I would pay much attention to that 4-6 weeks out. Advertised h5 height anomalies are probably marginally better at that range, but still plenty of uncertainty.

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1 hour ago, StormchaserChuck! said:

My Summer N. Atlantic SST = Winter NAO index, is 9-1-4 in the last 14 years. It was more than 1.5SD off last Winter, but the average SD is 0.55. It comes in at -0.15 for the Winter, about Neutral. (Warm upper box is negative, Cold lower box is negative). I would say that's -0.10 even. 

LdwzrQe3t0.png

So you are predicting a neutral-slightly negative NAO overall for the winter months?

 

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4 hours ago, frd said:

NAM state still looks uneventful.

Meanwhile

 

Today's 46-day ECMWF shows a +4-5°C anomaly for the full month of December in the north-central USA (vs 20-year climatology). At face value that would rival the warmest Decembers on record in Minnesota, such as 2015 and 1997 - both super El Niño winters
 
 
 
Image

@frd Just to add to your post, evidence is certainly mounting for a +NAM this winter, here is the thread Griteater made today: 

 

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Capital Weather Gang going with slightly below normal snowfall.  Hopefully the link isn't paywalled.

Reagan National Airport (DCA): 10 to 14 inches (compared with a 15.4-inch average, 11-inch median)

Dulles International Airport (IAD): 14 to 18 inches (compared with a 22.0-inch average, 16 inch-median)

Baltimore-Washington International Marshall Airport (BWI): 14 to 18 inches (compared with a 20.1-inch average, 15-inch median)

Fairfax, Loudoun, Montgomery counties: 12 to 20 inches

Alexandria, Arlington and Prince George’s counties and the District: 10 to 16 inches

DEC +3

JAN +1-2

FEB +1-2

https://www.washingtonpost.com/weather/2020/11/18/washington-dc-winter-outlook-2020-21/

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10 minutes ago, jaydreb said:

Capital Weather Gang going with normal to slightly below normal snowfall.  Hopefully the link isn't paywalled.

Reagan National Airport (DCA): 10 to 14 inches (compared with a 15.4-inch average, 11-inch median)

Dulles International Airport (IAD): 14 to 18 inches (compared with a 22.0-inch average, 16 inch-median)

Baltimore-Washington International Marshall Airport (BWI): 14 to 18 inches (compared with a 20.1-inch average, 15-inch median)

Fairfax, Loudoun, Montgomery counties: 12 to 20 inches

Alexandria, Arlington and Prince George’s counties and the District: 10 to 16 inches

DEC +3

JAN +1-2

FEB +1-2

https://www.washingtonpost.com/weather/2020/11/18/washington-dc-winter-outlook-2020-21/

Surprised they went with that snowfall prediction. Would speculate lower. 

 

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1 hour ago, snowman19 said:

From HM earlier: 

 

Interesting read. I can't find it at the moment, but I believe HM tweeted earlier in the Fall about how smoke plumes tend to increase the stratospheric temperature gradient, and that, in turn, would lead to a stronger PV and +NAM state. The lack of heat flux in the polar stratosphere that has been observed this season would also likely contribute to that, although not sure of/if there's a relation between that and aerosols from the western US fires. 

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