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NYC/PHL January 25-27 Potential Bomb Part 6


earthlight

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I'll tell you what. I initially doubted this storm tremendously given the height pattern and upper air blocking breakdown, but it's becoming clear that this could very well mean business if tonight's model guidance even has a semblance of a clue. I know there were plenty of people calling last weeks storm "mundane" (which it did end up being for most people), but this is the exact opposite of that should it come to fruition. The upper level shortwave is absolutely loaded with tons of vorticity--there's a very favorable baroclinic zone which the surface low's have been developing on all year. It's no coincidence the banding has liked to develop in the same areas. With the cyclone rapidly maturing and the favorable positions of the closed H7/H8/H925 lows which we have seen modeled (with a few bumps and jogs west and east here and there), there is some good support developing for more heavy deformation banding to develop underneath the Cold Conveyor Belt.

I would actually favor two areas of deformation that could legitimately make this a big snowstorm. One would be as the surface low initially develops off the coast--probably over West Virgina and in the immediate burbs of DC/BWI. Another should develop as the surface low undergoes rapid intensification along the aforementioned baroclinic zone. This is the big classic "comma-head" development the guidance is trying to key in on this evening. We can see it clearly on the NAM banding graphics which show the 800-600mb frontogenesis. This is a very useful tool for trying to pinpoint where the model guidance is actually trying to put the banding..not where the QPF shows it's heaviest. Regardless the NAM...in agreement with most other models (RGEM/MM5/etc) has the banding developing first near DC (click here for the DC banding image)...and then the big band developing overhead. That image is below. Trying to pinpoint the area this band will sit over is nearly impossible at this range...but it's safe to say that areas like Western LI...Central/Northern NJ..SE NY...SW CT and especially into Southern New England should be on high alert this point...for the potential for another one of those "classic" frontogenically forced bands which have the potential to dump prolific snow amounts in short periods of time.

51 hr banding over PHL (54 hrs is below)

frontb54.png

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I loved the "Western LI" line, John. :snowman: :snowman: :snowman:

I gave up hope on this a few days ago also, but this kind of banding signal and tremendous potential for lift/dynamics as the whole storm consolidates and congeals should be hugely thrilling for all of us at this point.

It's almost as if there are "two storms" before it comes together when the dynamics "catch" the surface storm late Weds, but when it all does, BOOM.

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I loved the "Western LI" line, John. :snowman: :snowman: :snowman:

I gave up hope on this a few days ago also, but this kind of banding signal and tremendous potential for lift/dynamics as the whole storm consolidates and congeals should be hugely thrilling for all of us at this point.

It's almost as if there are "two storms" before it comes together when the dynamics "catch" the surface storm late Weds, but when it all does, BOOM.

I had to throw you guys in there :thumbsup:

There's still plenty of bust potential on either side of the ballgame, although I think the mid level temperatures are becoming less of a concern at least during the banding. Most of the models have gotten so much colder the past few runs. My concern right now would be the usual deformation/subsidence and all that--and obviously the progression of the upper level trough/shortwave and the interactions of a few shortwaves which are embedded in the flow.

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I have a lot to look forward to with this storm, at least if the most recent model output is any indication. Being in center Chester county, the storm start (mixing issues) seems to be up in the air (possible start as ZR/IP seems likely, but how quick is the changeover.) But, we also seem to be right in the bulls-eye for snow totals (at least when it comes to the clown maps for the area.) Can't wait to see how this all plays out, after being on the western fringe of the recent major storms. Do we see a foot like recently suggested, how long does the warm air hold, how perfect is the setup for the balance of QPF and frozen precip? Time will tell, but man will I be on the edge of my seat til this gets going.

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I had to throw you guys in there :thumbsup:

There's still plenty of bust potential on either side of the ballgame, although I think the mid level temperatures are becoming less of a concern at least during the banding. Most of the models have gotten so much colder the past few runs. My concern right now would be the usual deformation/subsidence and all that--and obviously the progression of the upper level trough/shortwave and the interactions of a few shortwaves which are embedded in the flow.

It has to develop in time. That's my main concern-that the 700 and 850 features especially, and hopefully 500 close off and really develop the kind of lift and dynamics we need. And obviously the track matters, since there looks to be a huge punch delivered over a fairly consistent swath. We could trend colder at this point, but if the dynamics and lift weaken or trend south, a lot of us will be disappointed anyway.

Amazing how this winter continues to deliver though. EPIC.

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i'd be cautious with using the high res models past 18-24hrs... didn't really do to well the lats system outside that time range.. Just food for though. Awfully quiet for a snow storm potential in here..

Waiting for Dr No to say Yes; It is scary when the models are in this much agreement.

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The scary thing Earthlight is that @ 51 hours the Sunymm5 is just getting going. Temps have plummeted, and theres heavy precip from the ULL all the way out to the WVa/Va border.

Classic, awesome run.

Here is what I mean:

boomb.gif

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I agree there. The heaviest dynamically driven snow is still over NoVA then, and it looks thereafter to consolidate and intensify even more on its way NE. :snowman:

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Frankly it's remarkable just how much of a shift in guidance we have seen over the past 36 hours. A definitive cold conveyor belt signature is evident on the mesoscale models, along with major backlash snows in what ultimately amounts to a relatively mediocre synoptic setup. For that reason, I'm wary of the high bust potential with a these ingredients at play. I've mentioned already that many models have a tough time with dynamic cooling situations, especially from a cold conveyor belt which is bound to set up a significant deformation band somewhere.

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