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December 2021


MJO812
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Most of us have a shot at maybe a dusting to an inch tonight through tomorrow morning. Then maybe something wintry on Monday. These could be our best threats for a while. Even if the Pacific ridge shifts east, the trof axis will still be pretty far west. Without a helpful NAO phase, we could be looking at a lot of cutters and rain. Most of us would probably be willing to roll the dice, but there's no guarantee that a "pattern change" will increase our snow threats.

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1 hour ago, bluewave said:

EPS weeklies continue the Aleutians ridge  and - PNA for the whole run. The -AO slowly weakens over time.  This could turn out to be one of the most impressive December into January -PNA patterns on record.

Dec 27 to Jan 3

AE4AB634-3C5B-4266-97F9-18B8E3138A56.jpeg.fed01dadb4f2b7d483287207374f57d5.jpeg

 

Jan 3 to Jan 10

 

CDDFE2C5-54FC-4E38-9006-8D8050E827F7.jpeg.3965cdd698ab12dea828b94b1fe9fe05.jpeg

 

Jan 10 to Jan 17

 

CADAF528-C999-436B-9BC3-DCDFC3F2B999.jpeg.dca9a24109891ee266c1be26ec19c270.jpeg

 

 

 

 

 

That's gonna be a historic winter out west. Really good for the drought situation. 

Highs in the teens possibly and single digits lows for Seattle. Below zero for Vancouver. This after 115-120F temperatures last summer. 

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Overnight, a system could bring a coating of snow north and west of Philadelphia, Newark and New York City. There is a small chance that one of these cities could pick up a measurable amount. It will then turn milder tomorrow. Afterward, a generally mild remainder of December lies ahead.

It will be a different story in the Pacific Northwest. Near record to record cold, along with snowfall, is possible during the closing days of December in such cities as Portland, Seattle, and Vancouver.

January will likely commence with an AO-/PNA- pattern. That typically favors somewhat cooler than normal readings in the East. For NYC, the January 1-10, 1991-2020 mean temperature for such cases was 33.5° (normal: 34.8°).

The latest guidance suggests that temperatures could head toward seasonal levels and then periodically below seasonal levels as the first week of January progresses. The coldest air will likely remain confined to the Pacific Northwest, Northern Plains, and western and central Canada. No severe cold is likely through at least the first week of January. There are some hints that a milder pattern could begin to develop around mid-January.    

In the Midwest, through 4 pm CST today, Chicago has yet to receive its first measurable snowfall. The old record latest first measurable snowfall was December 20, 2012.

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.7°C and the Region 3.4 anomaly was -1.1°C for the week centered around December 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.15°C and the ENSO Region 3.4 anomaly has averaged -0.93°C. La Niña conditions will likely persist through meteorological winter.

The SOI was +8.46 today.

The preliminary Arctic Oscillation (AO) figure was -1.419 today.

On December 21 the MJO was in Phase 7 at an amplitude of 2.341 (RMM). The December 20-adjusted amplitude was 2.099 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 43.1° (4.0° above normal). That would tie 2021 with 1998 as the 6th warmest December on record.

 

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1 hour ago, bluewave said:

The EPS weeklies were pretty consistent since early December in showing a strong -PNA continuing into January. But there was a quick flip to more of -AO in mid-December. So some people took this a good change. But several of us were pointing out that we needed improvement on the Pacific side to make things work. There were even a couple EPS runs that tried to push the ridge a little closer the the West Coast that backed off after only a few runs. While models can see an important signal like the -PNA long range, it verified much stronger the closer we got. The whole Aleutians ridge feedback process really took off. 
 

Dec 23 EPS run for Dec 27 to Jan 3

 

14DE7C4C-0609-4EA6-9F93-C158C6FEF7A0.jpeg.7c23720c55bc3ec70bdf82d56edcf6b7.jpeg

 

Dec 6 run for Dec 27 to Jan 3


862BE38B-220F-433A-B1A2-2405CE5FF412.jpeg.ef37d9807baf534b2def9b1f89949882.jpeg

 

 

I still think we get our snow chances once the NAO relaxes and allows a few cutters to get the colder air east. This would allow for weaker trailing waves to produce.

The NAO is hurting us here.

Hey if we can snow in Feb 2018 when it was 70 the day before......

 

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1 hour ago, jfklganyc said:

I think it was an echo chamber of wish-casting…but Im not the prediction expert others are.

Very early on seemed like a tail chasing the dog

I don't think the METS on the forums were wish casting when they said January held promise. The ensembles we're heading there. It just fell apart to some extent. 

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46 minutes ago, EastonSN+ said:

I don't think the METS on the forums were wish casting when they said January held promise. The ensembles we're heading there. It just fell apart to some extent. 

Exactly

All the long range models had a nice December and that's typical  for a lil Nina winter 

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