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Met Winter 20-21: Pattern Drivers & Evolution


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While there's reasonable agreement on a -AO and -NAO persisting into early January, there is some uncertainty WRT whether or not the Pacific side offers any help or not. The EPS develops a +EPO into e

I'm starting to get a little more excited for early-mid December. It looks like the Pacific jet will retract significantly, which is the real reason for the retrograding Alaskan LP. Upper level diverg

I think that we are going to see a pretty impeccable 500mb pattern after January 10th.    The -NAO originally forced by wave breaking (which is occurring in the very near future) will become

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1 minute ago, PB GFI said:

 

There's nothing left. 

 

image.png.6e5d069e3148ead87032d96ecfa9d8ff.png

I'm a big fan of the notable ridge in the Beaufort Sea extending poleward out to 324! Is there some destructive interference underneath? Maybe a bit. But you're getting quality PNA ephemeral spikes in there for sure with the possibility of cross polar flow rearing it's head with that look. 

 

Naturally I'd like the ridge axis to be centered a bit west, but who's complaining at that look at this lead time. :)

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3 minutes ago, PB GFI said:

Widen out its working towards a full latitude ridge 

 

image.png.5e5bcfbc94d5bb4df87a8500ed0b140d.png

Chef's kiss. 

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Just now, CCB! said:

I'm a big fan of the notable ridge in the Beaufort Sea extending poleward out to 324! Is there some destructive interference underneath? Maybe a bit. But you're getting quality PNA ephemeral spikes in there for sure with the possibility of cross polar flow rearing it's head with that look. 

 

Naturally I'd like the ridge axis to be centered a bit west, but who's complaining at that look at this lead time. :)

 

I would like this displaced further E , but this is clearly aided by the killing of the 70/90 by the ridge. 

 

image.png.ae230b96b31f7689f33cdbaa7804b216.png

 

So the higher heights are just filling in. 

I just like shutting off the PAC flow into W Canada.

 

 

Screenshot_20210101-190852_Chrome.jpg.86d9fdd3c4423f011975d82beae2796a.jpg

 

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1 minute ago, PB GFI said:

 

I would like this displaced further E , but this is clearly aided by the killing of the 70/90 by the ridge. 

 

image.png.ae230b96b31f7689f33cdbaa7804b216.png

 

So the higher heights are just filling in. 

I just like shutting off the PAC flow into W Canada.

 

 

Screenshot_20210101-190852_Chrome.jpg.86d9fdd3c4423f011975d82beae2796a.jpg

 

Ok, yeah, I was looking at the one snapshot. But I read you here. If we were splitting hairs, I guess I was referring to the "top" of the ridge would be ideal if it were placed further W. The base, I see your point optimally being a bit east. But again, we're not splitting hairs anyway, so it's all good, lol. 

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Just now, CCB! said:

Ok, yeah, I was looking at the one snapshot. But I read you here. If we were splitting hairs, I guess I was referring to the "top" of the ridge would be ideal if it were placed further W. The base, I see your point optimally being a bit east. But again, we're not splitting hairs anyway, so it's all good, lol. 

 

The amount of SWs forecast in the flow is just off the charts. 

There's one on the SE and one dropping out of the N branch 

 

 

image.png.e069ff25c9e39cb06aac194d34cb93e7.png

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15 minutes ago, Nick Psomaras said:

Man, you guys are great! What's a good weather discussion without some debate? I will always encourage people to not only contribute their own thoughts but also to feel comfortable enough to argue against the majority. @Allsnow Keep doing what you're doing my friend, you seem very knowledgeable!

Well said 

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17 minutes ago, Nick Psomaras said:

Man, you guys are great! What's a good weather discussion without some debate? I will always encourage people to not only contribute their own thoughts but also to feel comfortable enough to argue against the majority. @Allsnow Keep doing what you're doing my friend, you seem very knowledgeable!

Those are very kind words coming from someone who has dedicated their life/future to this craft. I’m just a hobbyist who learns from quality posts from smart individuals like yourself. I thank you for that 

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I’ll play. There’s a lot of confidence here on the pattern - but I’d ask everyone to think “why might I be wrong?”   I’ve read this board over the last three years and with good interest.  My technical background is another field - but one that also requires probabilistic thinking.  I’d be interested to hear more of what the pros think the soft parts in their arguments are.  And if not, that’s cool too. 

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Most important thing here is ensembles are continuing to focus the highest heights from mainland Greenland and points SW...This will not be the Atlantic thumb ridge (east based) that we've been dealing with the past few days. The storm track in result will shift east. Simple h5 --> surface translation  

floop-gefs-2021010118.500h_anom.nh.gif

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I have never seen this many SWs in the flow. 

 

By day 16 , the flow is completely log jammed and there's no way at this distance which of those lobes are real. 

 

 

Screenshot_20210101-192459_Chrome.jpg

Screenshot_20210101-192520_Chrome.jpg

Screenshot_20210101-193103_Chrome.jpg

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1 minute ago, PB GFI said:

I have never seen this many SWs in the flow. 

 

By day 16 , the flow is completely log jammed.

 

Screenshot_20210101-192459_Chrome.jpg

Screenshot_20210101-192520_Chrome.jpg

Screenshot_20210101-193103_Chrome.jpg

-NAO magic right there, as the traffic piles up in the Atlantic you get longer lived and more frequent stormy activity. Just need that western ridge to advect cold air into the region and deter against cutter activity and then you've got a potentially productive pattern

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It's like a Rose Bowl Parade of floats the way the log jam of storms will occur. Traffic Jam on nay rush hour highway in a big city is another analog.

AS usual lets all be optimistic but add a touch of caution - just a touch.

 

 

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8 minutes ago, NotSparta said:

-NAO magic right there, as the traffic piles up in the Atlantic you get longer lived and more frequent stormy activity. Just need that western ridge to advect cold air into the region and deter against cutter activity and then you've got a potentially productive pattern

 

If the block gets back between HB and Baffin we are good.

 

Look at the crud thumb ridge in 3 days kept that SW east of the Mountains.

I think a HB axis will push them under. 

 

Now I have made no secret on how I have been super stoked about the pattern so where could this go sideways ?

Suppression, not cutters , not warm air and not Pac issues.

 

The risk is that the press is more than what you're seeing modled and some of the maxes gets squeezed south. 

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An area of sleet changing to rain moved into the big cities of the northern Middle Atlantic region this afternoon. Overnight, periods of rain are likely and the temperature will likely hold steady and then begin to rise. Tomorrow will become partly sunny and much milder. Readings will likely rise into the 50s in much of the region.

 

The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait.

 

Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPO continues to show a possible transition that could lead to a trough's moving into the East.

 

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter.

 

The SOI was +15.27 today.

 

Today, the preliminary Arctic Oscillation (AO) figure was -2.950.

 

On December 31 the MJO was in Phase 3 at an amplitude of 0.566 (RMM). The December 30-adjusted amplitude was 0.460.

 

A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere could begin to cool.

 

The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January.

In large account due to a very warm start to the month, January will likely feature above to much above normal temperatures across the northern Middle Atlantic and southern New England regions.

 

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5 minutes ago, donsutherland1 said:

An area of sleet changing to rain moved into the big cities of the northern Middle Atlantic region this afternoon. Overnight, periods of rain are likely and the temperature will likely hold steady and then begin to rise. Tomorrow will become partly sunny and much milder. Readings will likely rise into the 50s in much of the region.

 

The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait.

 

Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPO continues to show a possible transition that could lead to a trough's moving into the East.

 

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter.

 

The SOI was +15.27 today.

 

Today, the preliminary Arctic Oscillation (AO) figure was -2.950.

 

On December 31 the MJO was in Phase 3 at an amplitude of 0.566 (RMM). The December 30-adjusted amplitude was 0.460.

 

A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere could begin to cool.

 

The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January.

In large account due to a very warm start to the month, January will likely feature above to much above normal temperatures across the northern Middle Atlantic and southern New England regions.

 

 

Don, the EPS first 15 days are now roughly plus 3.

It's cooled considerably.

 

I think the back 2 weeks have the ability to get those anomalies to N 

 

 

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15 minutes ago, PB GFI said:

 

If the block gets back between HB and Baffin we are good.

 

Look at the crud thumb ridge in 3 days kept that SW east of the Mountains.

I think a HB axis will push them under. 

 

Now I have made no secret on how I have been super stoked about the pattern so where could this go sideways ?

Suppression, not cutters , not warm air and not Pac issues.

 

The risk is that the press is more than what you're seeing modled and some of the maxes gets squeezed south. 

Totally agree, the Atlantic blocking is a little overbearing on the guidance so I could see the +PNA spikes only serving to produce further south. By then the NE might be willing to get a cutter so it can get a little further north lol

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20 minutes ago, donsutherland1 said:

An area of sleet changing to rain moved into the big cities of the northern Middle Atlantic region this afternoon. Overnight, periods of rain are likely and the temperature will likely hold steady and then begin to rise. Tomorrow will become partly sunny and much milder. Readings will likely rise into the 50s in much of the region.

 

The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait.

 

Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPO continues to show a possible transition that could lead to a trough's moving into the East.

 

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter.

 

The SOI was +15.27 today.

 

Today, the preliminary Arctic Oscillation (AO) figure was -2.950.

 

On December 31 the MJO was in Phase 3 at an amplitude of 0.566 (RMM). The December 30-adjusted amplitude was 0.460.

 

A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere could begin to cool.

 

The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January.

In large account due to a very warm start to the month, January will likely feature above to much above normal temperatures across the northern Middle Atlantic and southern New England regions.

 

Bunch of bold calls in here, good luck Don.  Against the grain of this board for sure

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