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Winter 2020-21 Discussion


CAPE
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1 hour ago, poolz1 said:

Agreed.  I dont see how we avoid significant bouts of a very unfavorable pac.... We'll be constantly teased with models showing an eastward progression of the MJO and therefore a better looking long range signal in the Pac. 

At least in this weenie mind, trying to find a silver lining, the 2 main features that seem to stick around on ensembles are the low heights west of the Aleutians and the higher heights in the Scan region.  If we can maintain the features somewhat, maybe we can periodically offset what will be occurring in the Pac. Keeping the PV in check and giving us bouts of HLB.  As the MJO tries to push into more fav areas, dies and then reemerges over unfavorable areas....these occurrences may be our windows of opportunity this winter?

Or, maybe nothing works out as planned (like last year) and we end up with these looks on the regular! :weenie:

509KFe2.png

I did read from a couple of sources that at least for the time being the likelyhood of the trop and stat pv linking is low. Also some overall lack of structure.  AO still progged to decline after November 6 th. 

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3 hours ago, poolz1 said:

Agreed.  I dont see how we avoid significant bouts of a very unfavorable pac.... We'll be constantly teased with models showing an eastward progression of the MJO and therefore a better looking long range signal in the Pac. 

At least in this weenie mind, trying to find a silver lining, the 2 main features that seem to stick around on ensembles are the low heights west of the Aleutians and the higher heights in the Scan region.  If we can maintain the features somewhat, maybe we can periodically offset what will be occurring in the Pac. Keeping the PV in check and giving us bouts of HLB.  As the MJO tries to push into more fav areas, dies and then reemerges over unfavorable areas....these occurrences may be our windows of opportunity this winter?

Or, maybe nothing works out as planned (like last year) and we end up with these looks on the regular! :weenie:

 

Been tracking this for awhile on the extended GEFS and EPS weeklies for mid to late Nov. Good to see it showing up on recent op and ens runs now that they are in range.

The look on the12z run today would probably suppress the storm track so far south we would miss all the cold rain.

 

 

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On 10/30/2020 at 4:41 PM, DTWXRISK said:

I haven't been  through  the entire thread in this group or in the general forums but I am increasingly bothered by the amount of groupthink regarding the winter.

 it seems the data is overwhelming that the La Nina  whether it's moderate or strong …  only reaches that intensity for short interval of time  -  DEC - and that the La Nina is going to significantly weaken in the second half of the winter. Again I do not know if others have mentioned this but seems to me that this  is being overlooked buy a lot of folks and I think this is a huge mistake

 The second issue has to do with the amount of incredibly warm water that is piled up in the Eastern Pacific  along the immediate west coast of Canada and the Gulf of Alaska. I have looked on the SST maps   on  weatherbell and  weathermodels   sites  along with other sources and so far I have yet to see a La Nina  with that much warm water piled up with that sort of intensity along the west coast of North America.

 Maybe somebody else has found something that matches it but so far I haven't seen anything. So I am concerned that these the two things are being overlooked by a lot of people. 
 

I’m not sure how much the former factor will help. There is often a lag effect between enso and pattern and even a weak to moderate Nina isn’t exactly great snow climo in our area.  But I am very much in agreement on the latter. The pacific SST is really in contradiction between the enso regions and PDO regions. There aren’t very many good analogs to this configuration at all. I’m still being pessimistic but that’s probably just me not wanting to set myself up for a disappointment.  I could see a scenario where this year does not behave like a typical Nina. 

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1 hour ago, psuhoffman said:

I’m not sure how much the former factor will help. There is often a lag effect between enso and pattern and even a weak to moderate Nina isn’t exactly great snow climo in our area.  But I am very much in agreement on the latter. The pacific SST is really in contradiction between the enso regions and PDO regions. There aren’t very many good analogs to this configuration at all. I’m still being pessimistic but that’s probably just me not wanting to set myself up for a disappointment.  I could see a scenario where this year does not behave like a typical Nina. 

Man, after stuff not working the way it does...it would be nice to have a GOOD "this didn't behave the way it should have" happen...shoot, stupid weak nino of 2018-19 didn't behave the way we it should have, so any good fluke would balance it out! :D

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As October comes to a close, it’s interesting that the temperature profile across the US For October 2020 did not match the average profile for October La Ninas over the last 10-15 years.  Throw into the mix that long range climate outlooks from the JAMSTEC and Cansips crapped the bed for the October temperature forecast (made in Sept) and maybe this upcoming winter won’t be as predictably bad as many are expecting. 

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I’d be ok with Cosgroves thoughts....

 

MONTHLY FORECASTS
 
NOVEMBER
 
Most of the analog years present a fairly standard +PNA signature with a warm West vs. cool Central, East alignment. But a recurrent issue is that all model guidance is solidly warmer than normal over most of North America. Given that the comparison test looks almost exactly like the same September 1 - October 16 of this year, I kept the temperature forecast very close to the twelve-year mean.
 
If shortwave injections into the Mid-Continent mean trough are as strong as what is shown now over the northern Pacific Ocean, potential for high wind events will be high from the Rocky Mountains into the Mississippi Valley and Great Lakes in November.
    
DECEMBER
 
A more difficult forecast, since there is a prominent warm-up across the Old South and Mid-Atlantic regions which may not be viable. Note the positive height anomaly in the -NAO position (Baffin Island and Greenland) which in many cases could be construed as a block that triggers southward deviation of the jet stream. That said, the numerical model guidance is very aggressive in presenting a Southeast ridge. That feature is normally linked to very warm conditions east of the Rocky Mountains. The gradient set-up between recurrent storms over MT and WY vs. the ridging implies repeated high surface wind potential from the Great Plains and Texas into the Corn Belt.
 
Caveat: Should the high-latitude anticyclone be the stronger of the two ridges, temperatures will be much colder across the Midwest and Northeast than what is shown here.
    
JANUARY
 
A much colder outlook than the previous attempt. The presence of ridging in the -EPO, -AO, and -NAO positions normally favors relocation of the cA vortex at 500MB into Ontario and James Bay. Indeed, with the core negative height anomaly aloft centered roughly over MN and W ON cold pooling will probably relocate to between the Rocky Mountains and Appalachia. The surface storm track may stay inland over the Piedmont and Atlantic Coastal Plain, so the major cities may have cases of rain and not snow. All things considered, there will likely be some very wintry moments in the Midwest and Great Lakes. The western states seem warmer and drier than normal outside of a few frontal passages along the Pacific Coast.
 
Caveat: It would not take much, with the widespread ridging at higher latitudes, to turn the Eastern Seaboard into a winter wonderland as we start 2021.
    
FEBRUARY
 
Similar in many ways to the January upper air pattern, but with more extensive cyclonic curvature and cold air through the eastern two-thirds of the nation. If there is going to be a major snowstorm along the East Coast, it probably will be in February. Note the stability of the blocking ridge complex above the Arctic Circle.
 
Caveats: If ridging builds into British Columbia, we could see cases of severe cold and more frequent frozen precipitation from the Great Plains to the East Coast. Conversely, if the blocking signature is weaker, there may be some merit in the very warm outlooks posted by the CFS and ECMWF series.
    
MARCH
 
Yet another example of a back-ended winter forecast. Note that there is very little change in high-latitude ridge position and strength. In theory, if this forecast verifies, abundant snow in the Great Lakes, Mid-Atlantic, and New England could help to maintain substantial cold to the right of the Continental Divide.
 
Caveats: The very warm numerical models continue to concern me, and are a reason that I moderated temperatures somewhat from the Mid-Atlantic to the Eastern Seaboard.
 
Curiously, all analog and modeled guidance suggests a turn to much warmer weather nationally as we enter April. But March should be cold.
 
SUMMARY     
 
Snow cover in the Northern Hemisphere does not look like anything special now. But given time, and ridging spaced about the North Pole and Arctic Circle, the strong polar westerlies acting in concert with a La Nina signal should produce vigorous storms in the middle latitudes. The dryness in the middle of the continent could limit snow in the Great Plains and Rocky Mountains. But if the analog predictions verify for the winter months, there will be a great deal of snow in the Great Lakes and Appalachia. The best odds on snow impacts along the Interstate 95 corridor appear to be for February and March. The two most active storm track threats: Alberta Clippers and "Miller B" Hatteras Lows (one of which could be a memorable winter storm). 
    
 A colder winter, overall, than the five most recent DJFM periods.
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2 hours ago, CAPE said:

The November edition of the CanSIPS is out. Pretty meh overall, but not as bad as last month. Typical boilerplate Nina look with little to no help in the AO/NAO domain. December and March have the "better" h5 looks. Positive temp anomalies throughout.

It was noted that the shoulder months of the winter might have the best potential due to the weaker state of the polar vortex

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35 minutes ago, JakkelWx said:

Cosgrove using 2009-10 as an analog for this winter which is a moderate la nina :lol:

 

22 minutes ago, Maestrobjwa said:

09-10 has to be the most abused analog in the history if winter forecasting, smh This has gotten absurd!

It’s one of 10 winters he used (and two others are emphasized and weighted heavier), and it’s not like he’s predicting 5 feet of snow. Personally, of his analog years, I’ll take a February ‘79 repeat and be very happy.

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I don't like mixing analogs that are on the opposite side of the spectrum...2007-08  can't be mentioned in the same sentence with 1995-96...thats just me...I see Larry has some big years on that list...for the record I think the winter won't be like either of them years...I think snowfall will be near average along with temperatures...give me 59-60 and I'll be happy...

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CFSv2 versus the GEFS strat forecats 

I have been keeping a record and noticing the verification between them, and it seems that the GEFS is schooling the CFSv2 in regards to strat forecast accuracy. 

This is actually not great news because I see a trend lately with the GEFS strengthening the PV as it slowly gets closer and closer to the ERA5 max. 

Another nail in the coffin in regards to achieving any significant or long lasting HL blocking. 

 

 

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13 minutes ago, frd said:

 

CFSv2 versus the GEFS strat forecats 

I have been keeping a record and noticing the verification between them, and it seems that the GEFS is schooling the CFSv2 in regards to strat forecast accuracy. 

This is actually not great news because I see a trend lately with the GEFS strengthening the PV as it slowly gets closer and closer to the ERA5 max. 

Another nail in the coffin in regards to achieving any significant or long lasting HL blocking. 

 

 

The TPV is much more influential on sensible weather. We can go an entire winter with little to no connection between the SPV and the TPV. I think sometimes it is forgotten that these 2 features are entirely separate entities. Probably not likely to see a sustained -AO if the SPV is unperturbed, but it certainly does not preclude blocking episodes and cold air outbreaks. We had plenty of "visits" from pieces of the TPV during the winter of 2013-14, and it had everything to do with the sustained -EPO/WPO, and little to nothing to do with the state of the SPV.

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3 minutes ago, CAPE said:

The TPV is much more influential on sensible weather. We can go an entire winter with little to no connection between the SPV and the TPV. I think sometimes it is forgotten that these 2 features are entirely separate entities. Probably not likely to see a sustained -AO if the SPV is unperturbed, but it certainly does not preclude blocking episodes and cold air outbreaks. We had plenty of "visits" from pieces of the TPV during the winter of 2013-14, and it had everything to do with the sustained -EPO/WPO, and little to nothing to do with the state of the SPV.

I did mention a couple days back that at the present time there is no direct link between the two ( SPV and the TPV ) and if anything the organizational structures are not ideal for linkage at this time. As I mentioned too, other factors may come into play in December and Jan. I do know that the WPAC warm pool is the warmest it has ever been , much different than 2013-14 and the current background state has never really existed with the significant Pac warmth focused  in certain areas against the strengthening Nina . Very interesting to see how things play out.    

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11 minutes ago, frd said:

I did mention a couple days back that at the present time there is no direct link between the two ( SPV and the TPV ) and if anything the organizational structures are not ideal for linkage at this time. As I mentioned too, other factors may come into play in December and Jan. I do know that the WPAC warm pool is the warmest it has ever been , much different than 2013-14 and the current background state has never really existed with the significant Pac warmth focused  in certain areas against the strengthening Nina . Very interesting to see how things play out.    

Yes it will be. I stated this a few times itt, and just my opinion- our best hope for occasional cold air intrusions probably lies with the orientation/ placement of the EPAC ridge. Hopefully ridging can establish towards the EPO domain for a time. Maybe we see a few transient -NAO episodes, but given the run of +AO/NAO winters we are on, and other factors that aren't necessarily favorable, it's difficult to be optimistic about the development of persistent HL blocking this winter.

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