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Met Winter 20-21: Pattern Drivers & Evolution


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A relatively quiet weather pattern remains in place. The dry weather could last through much of this week.

 

A strong flow of Pacific Air will push much milder air eastward. High temperatures could approach or break records in the Northern Plains tomorrow. The temperature could make a run at 50° on either Thursday or Friday in New York City before somewhat cooler air returns.

 

The first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada overall. After January 10, the EPS continues to shows a transition during which a trough will move into the East. During the second half of January, there will be some potential for snow events in the Middle Atlantic and southern New England regions. Afterward, the evolution of the AO will determine whether such potential continues into February. Uncertainty about the long-range has increased. There is emerging ensemble guidance showing that the AO could go positive in the closing week of January. That outcome would likely lead to a warmup near the beginning of February.

 

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.77°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through the winter.

 

The SOI was +17.39 today.

 

Today, the preliminary Arctic Oscillation (AO) figure was -0.705.

 

On January 11 the MJO was in Phase 3 at an amplitude of 1.243 (RMM). The January 10-adjusted amplitude was 1.384.

 

Following a significant stratospheric warming event, the stratosphere is now cooling. The mean zonal winds have reversed at 1 mb and 10 mb. They could still reverse at 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia.

 

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. Blocking appears likely to continue through at least the first half of January. There is emerging ensemble guidance suggesting that blocking could fade during the last week of January but there remains considerable uncertainty.

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 85% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.7°.

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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 hour ago, Grace said:

 

To me its just reckless for a professional weather outlet to make a tweet like this. With the exception of one single update (week before last) after week 3 the weeklies have consistently been showing typical climo moderate La Nina default look with +EPO, +NAO, +AO since mid-NOV. 

 

If one disagrees with a cold, blocky look I cannot think of a worse way for a professional met to argue their point by tweeting that. 

 

That outfit has consistently been doing this since mid-fall. 

 

1 hour ago, PB GFI said:

 

They have been pretty good, but their contention is that the LR GEFS is biased cold and the truth is, it is.

 

Except they fail to tell you how warm biased the LR EPS is.

I bit on the same EPS 1st 10 days of the month in January and it's plus 8 that they did. 

 

If you scroll through their site you will find a 7 day anomaly of plus 8 in NYC 

I saw the same EPS run and I didn't think the trough would be in the east until the 10th and I agreed.

( it got here by the 8th in the means ) just w N air. - 1 etc.

 

Well those 1st 10 days in NYC ended plus 3.

So the EPS busted by 5 degrees and that's massive.

But there was no mention of that. 

 

The story going forward isn't a 30 day mean of plus 2/3 in the east its the massive block in conjunction with a NEG EPO / WPO  that's going to make things very wintry in the MA and NE.

 

Mike Clarke is good and I get it there hate the GEFS bias which is real but there are bigger things in the means that could cause increased NG usage, like dropping 20 inches of snow on someone over a 25 day period and they aren't even looking at that. 

You’d probably need to read their actual report before contending much, they are a business after all, they try to get it right.

 

Doing long range is hard. I’m not going to blame anyone for trying.

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2 minutes ago, Snowy Hibbo said:

 

You’d probably need to read their actual report before contending much, they are a business after all, they try to get it right.

 

Doing long range is hard. I’m not going to blame anyone for trying.

 

I complimented Mike in my post. 

 

I said they were critical of the GEFS bias but omitted the EPS bias.

 

Not sure what you mean. 

 

 

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6 minutes ago, Snowy Hibbo said:

 

You’d probably need to read their actual report before contending much, they are a business after all, they try to get it right.

 

Doing long range is hard. I’m not going to blame anyone for trying.

Copying and pasting the euro weeklies is hardly making a forecast.

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2 minutes ago, Allsnow said:

Classic Colin  lol

 

 

Its pretty bad that BAMWX actually agrees with him. That doesn't say much about them.

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2 minutes ago, Jake302 said:

 

IIRC a PV lobe over eastern Canada is the best spot to get the most out of it. I remember DT saying something about that.

Correct

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No one had any of their core beginning before January 15th.

 

Now on Jan 12th, we are seeing threats emerge on the 19th and 23rd.

 

Not sure people could have pinned this period start better. 

So anyone complaining just isn't reading and if they are, simply not comprehending. 

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2 minutes ago, Allsnow said:

I hope we don’t waste on this blocking. Once in a lifetime in the heart of winter 


 

 

Wow!  If we can get the blocking to continue through February we are bound to start scoring some points.  

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I will take mid Jan through the end of February in a heart best.

A full 6 weeks is all anyone could dream up.

 

That would be occurring during the snowiest and Coldest climo wise.

 

Even if March is a stretch, any kind of blocking out there with short wavelengths would work. 

 

But Mid January through Feb , WOW

 

 

 

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1 minute ago, PB GFI said:

I will take mid Jan through the end of February in a heart best.

A full 6 weeks is all anyone could dream up.

 

That would be occurring during the snowiest and Coldest climo wise.

 

Even if March is a stretch, any kind of blocking out there with short wavelengths would work. 

 

But Mid January through Feb , WOW

 

 

 

Goes back to the guy that @Analog96talked to the older gentleman waiting on the great pattern to deliver the goods lol

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