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40/70 Benchmark

December 2020 Discussion

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Early signs are that that the PNA may begin the month a bit more favorable than expected.. There is also some support for perhaps some subtle disruptions of the PV during the month, which would be congruent with what was expected during the month of December. I do not expect the early month PNA to bare much if any fruit for the coast, as climo is relatively hostile and Canada is still largely void of cold. After about the 10th. cold reservoir be more replenished and climo will be less adversarial. 

I like the chances for a white xmas across a lot of the region....especially pike points north and outside of rt 128.

 

December 2020 Outlook

 
The polar vortex is likely going to begin the season quite consolidated near the pole during the month of November. However, the polar domain should become slightly less hostile to the development of periodic higher heights during the month of December, which may bring the AO and NAO closer to neutral, as dictated by previously referenced la nina climatology. This is when the more canonical, eastern pacific la nina regime will try to flex its muscle. Note the Aleutian high displaced to the northwest, and protruding poleward. The greatest positive height anomalies will likely be biased over the Aleutians, and to the east of Greenland, perhaps similar to the Ural blocking of October. This does not mean to imply excessive blocking for the period,  which is not constituted by higher Ural heights, but more likely at least some transient periods of positive heights at higher latitudes. Alaska should also predominately feature some higher heights, especially across the western portion. There should be continuous RNA, so there is warmer bust potential should the vortex remain more consolidated than forecast.
 

December Forecast H5 Composite:

 
Screen%2BShot%2B2020-11-03%2Bat%2B12.52.
 
 

December Forecast Temperature Composite:

There has only been one winter (DM) month, March 2018, that has averaged a negative NAO since February and March 2013. It is postulated that there is a high likelihood that we will add to that list this season. Most likely in December, but possibly March or even both. The month of December should average 1-2 degrees below normal for northern New England, near normal to a degree above normal for central southern New England, and 1-2 degrees above normal from north to south near New York City points southward into the mid atlantic. Cold will dump over the high plains and bleed eastward.
 
 
 
 
Screen%2BShot%2B2020-11-03%2Bat%2B12.58.
 

December Forecast Precipitation Composite:

 
It should be an active period marked by above average precipitation, especially for points north of Washington, DC. Primary modes of cyclogenesis include Alberta clippers, southwest flow events, and Miller B redevelopers, the latter of which especially prevalent during periods of negative NAO. New England should be favored for snowfall, especially central and northern parts of the region. The mid atlantic will need breaks in the RNA to coincide with negative NAO flex for significant snowfall, which is not exceedingly likely, but possible. A White Christmas is more probably than climatology would suggest this season. While the month is likely to average a negative NAO in the mean, this is not meant to imply that excessive blocking will reside for the entirety of the month.
 
 
 
 
Screen%2BShot%2B2020-11-03%2Bat%2B1.07.0
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1 minute ago, MJO812 said:

December actually looks good ( well the 1st half )

Not sure why you keep repeating this...it doesn't look that good. Especially further south where you are. Maybe into the 2nd week of December it's not a terrible look, but the first week looks like crap....you'd have to get lucky from the ULL in early December to get anything.

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1 minute ago, 40/70 Benchmark said:

I think "the first half of December shows signs of improvement" is more accurate.

 

Yes this is more accurate

 

20201123_124252.jpg

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1 minute ago, ORH_wxman said:

Not sure why you keep repeating this...it doesn't look that good. Especially further south where you are. Maybe into the 2nd week of December it's not a terrible look, but the first week looks like crap....you'd have to get lucky from the ULL in early December to get anything.

With the help of the PNA, we might squeeze something in.

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1 minute ago, 40/70 Benchmark said:

I think "the first half of December shows signs of improvement" is more accurate.

 

Right. The irony is that we’d have a better chance at snow with near blood red at 500mb and big surface cold like Dec ‘07. 
The beginning of the month looks like blues at 500 with 38F NE winds at the surface. :lol: 

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Of course yea the overall look gets better, but need money in the bank first. We start off broke.  If that look happened a month later that’s a different ballgame. 

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Man. Will went nuts on deleting solid posts. 
 

This Dec reminds me of one a couple years ago when everyone got excited about a + PNA , but Canada never cooled . And then the pig came back and never allowed the cold into Canada. I forget the year, but this looks eerily similar 

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Agree, Ray.

We’re really just using the first 1/3 to half of December to hopefully set the stage for a good latter half. I’m by no means a seasonal prediction guy but I’m looking at winter being a 4-6 week period starting in mid December. No clue how March turns out but wouldn’t be shocked if it got us to normal snow here. 

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This is a pretty solid look if we can reach this.....you actually have some cold replenish happening by this point. But again, this is near the end of the run....granted, it starts to look better by D12ish, but the EPS are still a little grouchier on the idea of that much amplification that soon.

 

 

Nov23_GEFS372.png

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1 minute ago, ORH_wxman said:

This is a pretty solid look if we can reach this.....you actually have some cold replenish happening by this point. But again, this is near the end of the run....granted, it starts to look better by D12ish, but the EPS are still a little grouchier on the idea of that much amplification that soon.

 

 

Nov23_GEFS372.png

Ha, was just going to post that. Bit of a split flow, but stout ridging in NW Canada was starting to get colder air into the US. Actually, in this case it would help to have a more +NAO as shown, otherwise too much garbage air is recycled in. 

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1 minute ago, CoastalWx said:

Ha, was just going to post that. Bit of a split flow, but stout ridging in NW Canada was starting to get colder air into the US. Actually, in this case it would help to have a more +NAO as shown, otherwise too much garbage air is recycled in. 

Do you mean due to the stagnation of a neg NAO...IE, not allowing the old Pac puke to bleed out?

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1 minute ago, CoastalWx said:

Ha, was just going to post that. Bit of a split flow, but stout ridging in NW Canada was starting to get colder air into the US. Actually, in this case it would help to have a more +NAO as shown, otherwise too much garbage air is recycled in. 

This is actually how December 1975 turned good for New England after starting off the month like garbage. Despite being a strong Nina, we got an Aleutian low and western ridging with a +NAO/+AO. Hopefully we can get something similar

 

 

 

Dec1975_15-25.gif

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21 minutes ago, ORH_wxman said:

This is actually how December 1975 turned good for New England after starting off the month like garbage. Despite being a strong Nina, we got an Aleutian low and western ridging with a +NAO/+AO. Hopefully we can get something similar

 

 

 

Dec1975_15-25.gif

I only used it as a secondary analog because of the ONI and MEI criteria that I employed, but that season is one of the better sensible weather analogs for how I see this winter playing out. Even the blocking just east of Greenland was a very prevalent feature in my composite.

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31 minutes ago, 40/70 Benchmark said:

Do you mean due to the stagnation of a neg NAO...IE, not allowing the old Pac puke to bleed out?

Yeah, see Will’s post below yours.

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Funny, the Euro is trying to thread the needle the first few days of December. It's an unlikely scenario, but you can sort of see how it would be done....timing the southern stream with a northern stream wave, and that will be marginally cold enough.

EPS show a hint of it too.

 

Nov23_EPS216.png

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7 minutes ago, qg_omega said:

Pattern would favor NC for multiple chances

Agree as it stands today. Blocking looks too strong. 

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Best wishes and hopes for marine interests ...

 

Fwiw, this cycle of the oper. Euro taking steps toward expected correction... Still ends up odd-ball looking at the end of the run, but it's sequencing through a more progressive N/stream now, and I suspect that full stalled Lakes look is in trouble...

We're likely to see an r-wave signal pass through the east with this +PNA ...but that's different than the previous Euro/GGEM attempting to conserve it into a singular gyre like previous runs.

Not that anyone's paying attention - lol... just sayn'

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9 minutes ago, Typhoon Tip said:

Best wishes and hopes for marine interests ...

 

Fwiw, this cycle of the oper. Euro taking steps toward expected correction... Still ends up odd-ball looking at the end of the run, but it's sequencing through a more progressive N/stream now, and I suspect that full stalled Lakes look is in trouble...

We're likely to see an r-wave signal pass through the east with this +PNA ...but that's different than the previous Euro/GGEM attempting to conserve it into a singular gyre like previous runs.

Not that anyone's paying attention - lol... just sayn'

Euro ensembles are kind of a mess....not very cold, but there is a chance if things line up perfect. You can see the PNA ridge which has been there all along, but the plethora of waves to the east are kind screwing with the solutions. I agree with you that the stemwinder cutoff in the lakes is unlikely.

 

 

Nov23_EPS204H5.png

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1 minute ago, Damage In Tolland said:

Just bags and bags full of them tossing them off the sleigh into S Wey, Brooklyn and Metheun

More like Brooklyn and Bolton Landing. Tony rolls his window down in his patrol car, and piles of hotdogs roll out along with this laptop stuck at hr 240 on the euro op. 

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