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Met Winter 20-21: Pattern Drivers & Evolution


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Atlantic Ridge and subsequently negative NAO regimes dominate today’s ECMWF extended-range through mid-February, with a relative absence of Scandinavian Blocking. This time last year, these charts were a sea of blue (NAO+)! A cold outlook for northwest Europe.
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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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2 hours ago, Allsnow said:

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I was just going to write how I would sign up for this type of look in a heart beat. Overdubbing galore with clipper and Miller B opportunities 

 

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2 hours ago, PB GFI said:

New week 3 

 

1612310400-rT2G7TxsZH4.png

 

Old week 4 

 

 

1612310400-LdblK8cJDyU.png

 

 

 

As I posted earlier. 

It's why I maintain the 15 to 15 period. 

 

image.png.658a209ce5734346cba417d75a5c25a5.png

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Definitely some good positive changes in the long range ensemble guidance today that have shifted further away from the concerns I posted earlier this week. Still plenty of time for further changes, but good looks today.

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10 minutes ago, brooklynwx99 said:

absolutely incredible pattern progression

 

the N Atlantic is completely blocked, and a large trough is forced over the NE

 

this will both allow arctic air to drain from the NW US, as well as stop systems from cutting and force them to redevelop 

 

as i’ve said before, the GEFS is also most likely breaking the block down too quickly, but the 120dam anomaly in Hudson Bay is still nothing to sneeze at

 

AF400016-5B0A-4324-9060-E23DE4831A07.gif

 

 

 

The retrogression in the Atlantic is classic.

 

A March 18 of Feb 10 set up may be taking shape in late January.

 

So the stakes get raised a little due to the nature of the coldest time of the year with a very similar set up. 

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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. On Wednesday, high temperatures could approach or break records in the Northern Plains. 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 +15.17 today.

 

Today, the preliminary Arctic Oscillation (AO) figure was -1.056.

 

On January 10 the MJO was in Phase 3 at an amplitude of 1.343 (RMM). The January 9-adjusted amplitude was 1.444.

 

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.

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 84% 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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2 hours ago, PB GFI said:

 

As I posted earlier. 

It's why I maintain the 15 to 15 period. 

 

image.png.658a209ce5734346cba417d75a5c25a5.png

 

 

This gives validity to week 3 of the weeklies.

 

Simon Lee (@SimonLeeWx) Tweeted:
Looking in 2D phase space (here for week 3), we can see confidence in the combined negative NAO (EOF1) and Scandinavian Trough (negative EOF2) https://t.co/7aBJNib9a1

 

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On 12/1/2020 at 4:56 PM, PB GFI said:

 

SSW is " forecast " in 20 plus days then there's a lag ( 30 days before we see the effects) and between now and then we have no way of knowing where the anomalies land. 

 

Dec 20 to Jan 10 probably has the ridge in the east and we go AN, that's why I am humping the period before then because the trough is retrograding in the means. 

 

We want to score some points before we go back to cutter cold cutter cold. 

 

I don't know if I have ever had a better season in here. 

 

Go check out my 30 day outlook posted 2 pages back 

I think every idea is on its way.

 

 

If anyone had better visibility this year I would love to see it so before you ever tell me to temper my ideas @Allsnow you should feel free to go back and read this stuff 

 

 

I have a core Jan 15 - Feb 15 and I think something very substantial is coming. 

 

But seriously don't tell people what they should forecast especially me , if stuff busts I will always take responsibility

 

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1 minute ago, MI Storm said:

Thing that excites me most is the EPO changing. Feels like it's been forever. 

 

EPO / WPO are game changers 

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Just now, Allsnow said:

I didn’t ask you to recap your ideas. Believe me, I think the forum is well aware of what you have called for this winter. My only suggestion was to not compare a favorable period to some of our historic stretches of winter weather. All we can ask is that a potential for winter weather looks to be coming. All that means is instead of no chance we have a better then that chance. Seeing terms like snowmaggeddon2 or March 2018 in January just sends off a unrealistic vibe. I don’t think people understand how lucky you need to get in some area for memorable stretches to happen

 

I think a very substantial period is coming.

Why shouldn't I put the data out that supports it .

 

Do I think a March 18 / Feb 10 option is on the table ?  I do.

 

Can it blow up and wreck everything I put out since late November ? Of course.

 

But imagine if I posted , Timmy stop posting your ideas because it makes people feel etc.

 

I am fairly confident that this is evolving into a really good period.

 

Some think it's 10 days and a cloud of dust and that's their right. 

 

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11 minutes ago, PB GFI said:

 

I don't know if I have ever had a better season in here. 

 

Go check out my 30 day outlook posted 2 pages back 

I think every idea is on its way.

 

 

If anyone had better visibility this year I would love to see it so before you ever tell me to temper my ideas @Allsnow you should feel free to go back and read this stuff 

 

 

I have a core Jan 15 - Feb 15 and I think something very substantial is coming. 

 

But seriously don't tell people what they should forecast especially me , if stuff busts I will always take responsibility

 

So your forecast for the end of the month is 09/10 or 2010? Noted.

 

 

i didn’t know you called for a ridge in the east from dec 20- Jan 10...wow 

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