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Met Winter 20-21: Pattern Drivers & Evolution

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1 hour ago, PB GFI said:


Just look at what I have been saying that the retrograting positive just kicks those negatives back towards the dateline. 

That's how the " pac weakens ".


Then you have a massive block centered over HB and Baffin.


Then the negatives get forced under. It's a process but the process is now underway and in the very early stages. 


It will begin to influence in 10 to 12 to 14 days and then it's off to the races. 


East Asia Rule suggests a trough in east somewhere in the JAN 6-10 time frame. 6-10 day correlation from the 30th




More in context of your comments, East Asia Rule suggests another trough somewhere in the JAN 13-17 time frame, which is close to the timeframe you're suggesting. 




Another teleconnection I use suggest the same as EAR. These teleconnections have performed so much better than the models have. 

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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, PB GFI said:


I agree 100% 


The 1st 10 days of the month really is a hostile regime, and even so you see snow chances from NNJ into NE during this horrible period, well because it's January and not December or March where you need a better source region and much colder anomalies.


But I said in the 30 day evolution post that the 1st signs that the block would be showing up and becoming an influencer would somewhere between the 8th and 10th where you would begin to see cutters get shredded.

Thats pretty much before any of this is even set.


If we look at the 0z operational runs tonight that's all you saw was weakening LP to the lakes getting forced to the Atlantic and forced to redevelop.


The 1st ones have to go to New England because even though the anomalies there are plus 8 they can snow in that regime in January with a good track.

As the block moves west our anomalies could be in the plus 4 for all I care but when you're in mid January all that matters is the mid level flow and the block at 500 over HB will find a way for you to snow. 


As we get deeper between the 10th through 15th, this all begins to come together.


So this morning the Canadian Jan 10 - 15 mean is beautiful.




When we get to the EPS day 13 14 15 which is only the BEGINNING and it is equally beautiful.







Oh and how fast could we couple? 










So the idea was the block would begin to influence the NE and obviously the mid latitudes in general around the 10th and really kick off my 15th to 15th period. 


One only has to see as the block retrogrades during the 1st week in January and see how it is KICKING that negative in ALASKA out and back towards the dateline.


The warm air that we and Central Canada eat early on is an actual precursor to one of the best mid January blocks I have seen in a long time.


Now once this block establishes itself its really game on and by that I mean we go from shredded out cutters to bowling balls to coastals as this gets back to its best Western axis.


And I agree with your assessment, its a matter of when not if and personally I can't wait until we get into the pattern of its either snow or no because that is what massive positive anomalies over Baffin Island can do.


Lastly for those yelling about the PAC, we said the block would solve this for you. One can already see the positive height anomalies creeping into ALASKA and  that's represented quite well with the AN anomalies there between the 12th and 15th and will create a - EPO over time. 


430 AM back to bed for a nap. But everything is on target except now the EPS is actually building the colder anomalies at the end of the forecast period and that is a positive for us.

PB and this to your arsenal I know it it is the 6ZGFS but you go from this


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Just now, Webberweather said:


We won't necessarily need a legit -EPO or a fully retracted Pacific jet to crank out a storm in this patter. The physical process of the jet pulling back from its most extended state is all it can take to trigger a transient +PNA & crank out a KU event w/ the giant west-based -NAO overhead. 


With a that grand of a - 2/3 SD NAO centered in that region I 100% agree and invite SWs in under the block .

In fact just wave space correctly and it's a party. 

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17 minutes ago, Snowy Hibbo said:


Just a short and sharp driver discussion on the blog about the two simultaneous situations, that are the SSW/Arctic and Pacific (but of course connected in their special way...).


Yes, I’m very positive, particularly about the Pacific for the latter two thirds of Jan and early Feb for the Eastern US snowfall forecast.


But yes, the SSW will be important to track, have added a few words of caution about the need for that block to hold in.



Snowy,  I understand better now with your detailed blog post regarding the Pac and how it will progresses to an improved state. Nice update.


Do you feel the SSWE can over-power any orbit into the IO, if it were to occur?  ( Based on the update from on your site).    Have you done any research on this ?  


  "We might see an orbit in the Indian Ocean, that could be a little destructive (for the Eastern US) to the current forecast if it comes to be later in January."



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6 hours ago, Dsnowx53 said:

The big NAO block retrograding is already helping lead to higher heights backing into Western Canada at the end of the ECMWF OP. Yes, the Pacific sucks right now, and maybe it does not necessarily get "great," but I am fairly confident that the pattern evolving will improve the Pacific enough so that when combined with the AO and NAO blocking, we should get our fair share of MECS threats.



We haven't seen a block this strong since January 2011.

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20 minutes ago, Webberweather said:

We don't need to change the N Pacific. Look at some of these monsters and how bad the N Pacific looked (esp Feb 78).


If you get a legit west-based -NAO like we're going to see by the 2nd week of January, there's almost always going to be a fighting chance of a big KU event regardless of what the Pacific is doing.






And the commonality continues to be that a SW dove in under a block with a well timed PNA spike during the " coldest time " of the season.


So even if the surface prior was meh, the mid level flow in mid January to mid February is more than cold enough as the block helps buckle the flow to cool the surface and bring you a KU.


That's what those blocks tend to during this time of the year. 


I think people keep missing the climo surrounding this blocking event and how a less than perfect set-up could still bring you a grand result. 





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