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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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Yeah the only real problem with the Pacific right now is extended jet that's keeping the PNA positive. I also think that people are underestimating the Atlantic block especially getting further out in time. It's able to shred up cutters but the issue is the block only goes so far south so the cutters still go north of NYC/NJ. Still, other areas like New England getting snow potential out of former cutters is impressive and speaks to the power of this block. Once it retrogrades, and we have a more positive PNA, it'll be far easier to get a storm out of that pattern. At that point something like a -EPO is just gravy

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4 minutes ago, Webberweather said:

Basically uninterrupted 50-50 low on today's GFS beginning at day 4 lasting thru at least day 10. Many of the classic pieces are already in place.

 

50574867.gif.10cd89d5f640884c7722abf068c8d4a3.gif

This is one of the pieces to the classic "snow begets  snow" pattern.

When you get enough lows somewhere near the coast, they can move to the 50/50 position one after another.

Then you can basically have a semi permanent 50 50 in place.

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10 minutes ago, Webberweather said:

Basically uninterrupted 50-50 low on today's GFS beginning at day 4 lasting thru at least day 10. Many of the classic pieces are already in place.

 

50574867.gif.10cd89d5f640884c7722abf068c8d4a3.gif

You know there's a beefy -NAO when you can have lows sit and spin like that. And also adds to my point about a NAO block not being overrated. You can't freeze up the Atlantic like this and slow down storms near the coast with a -EPO, ideally you'd want both, but even as you have extensively pointed out it's not a must. Nice work with finding the west-based -NAO KU storms!

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10 minutes ago, Archerdude44 said:

You’ve been nailing this stuff. Look at that pac!

 

Thanks I think there has been more than several members in here who have been on this entire evolution and the retrograting block kicking this off.

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Oscillating Aleutian low looks to be pumping the developing ridge out west during mid month period. Would be a god sent for snow lovers in the East Coast as undercutting ULL's will be given a chance to reach the Atlantic. At first glance you'd think "oh no" the persistent Aleutian low creates a +EPO setup...However the counteracting west based -NAO/-AO would be the driver in reenforcing the cold air. You can have a +PNA AND a +EPO across that domain, but it's important to have the Atlantic teleconnections in your favor and that is being well advertised on ensemble means. Here is the last 6 run mean of the CFS valid  Jan 10-16 

 

floop-cfs-2020123000.500h_anom_tle_6.nh.gif

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1 hour ago, PB GFI said:

After Jan 10- it`s game on.

 

And obviously there`s the 3/4 system and probably something else that will get pushed under even before this takes hold. 

 

 

 

 

1610712000-f3XB2FjCS20.png

 

Agree! While PAC improvement is not necessarily needed for east coast weenies. A little improvement is needed for OV or TN Valley folks....and I think its coming. 

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2 hours ago, PB GFI said:

After Jan 10- it`s game on.

 

And obviously there`s the 3/4 system and probably something else that will get pushed under even before this takes hold. 

 

 

 

 

1610712000-f3XB2FjCS20.png

That's a wonderful look if you want a KU. 

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