Monday, February 13, 2012

major east coast snowstorm? no. Major mid-atlantic snowstorm? maybe

I can't remember a time I've ever seen this much hype for a snowstorm thats still over 120 hours away. That's five days! It must be the kind of winter we're in. Snow lovers are ready to pounce on any sign of a winter storm, myself included. Before you read on, remember that the maps I show are just what the computer models are showing right now. Everyone knows it is foolish to predict exactly how a storm will act that far away. The models even did poorly on this past weekend's storm within 24-48 hours! With that being said, I must admit I'm excited with the prospects of snow we have going for us here in Virginia next weekend. Even if my house (Mcgaheysville just southeast of Harrisonburg) gets ripped again, as always, I'll enjoy the fact that you central VA folks get yours. I really hope you do. Maybe we all will. There are two main scenarios that I'm looking at right now, not to say that a compromise somewhere in the middle is out of the question, because this often times ends up being the case. The first scenario I'm going to show is what the GFS has indicated the past several runs.
Yes, the GFS does have the low.  Yes the GFS does take it up the eastern seaboard.  So what's the problem?  Look how elongated and weak that low pressure system is.  It's only a 1009 mb low off the coast of NC Sunday morning.  This low would not be able to provide an expansive precipitation field even worth noting.  Sure, eastern VA could see a few snow showers during the first half of the day Sunday, but that's about all it would be.  Winter weather lovers would be pounding themselves in the head.  So do I think this is going to happen?  This exact solution? No, I really do not.  I believe the GFS is failing do to one of its known biases, over doing the cold air spilling out of canada.  You can notice this over the great lake's area.  This essentially, in weather terms, suppresses the low.  Kills it.  Is the GFS ALWAYS overdone with the cold air?  No, of course not.  Sometimes its right.  So why do I feel like this time it is wrong?  This is the operational run of the GFS.  Ensemble runs of the GFS are ran by inserting slightly different data during the initializing steps of the GFS model run.  Why?  This is the exact reason why.  It can point out when the model may be a little off its hinges (in this case-over suppressing).  So lets take a look at the 18z GFS average of ensembles. 

So what's important here?  Well first, notice how the low is a bit more consolidated, and ALREADY a 1008 mb low over SC.  But most importantly..notice how the ensemble run averages are less aggressive with the cold air surging south from canada.  The operational run is indeed failing due to its known bias.  This shows it.  The GFS ensemble images end up tracking much closer to the coast before making its NE change in direction.  Could the GFS ensemble images be the the incorrect ones?  Well lets look at all the backup we have gathered from other models today in support of the GFS ensembles.

Here is the 12z Euro from earlier today.  It's track is favorable for Virginia.  Once again, notice how it is much like the gfs ensembles when it comes to the cold air invading from Canada. 

12z UKMET very similar..somewhat stronger...996mb....

 The NOGAPS, DGEX, , and JMA are also all favoring this track.  I wont post because you get the point.  So those were the 850 mb maps.  Here's what that would translate to at the surface.

18Z GFS Operational:
12z Euro :

18z gfs ensembles:


18z DGEX (my favorite lol)

So I'm breaking this down into two scenarios right now:
Scenario # 1:GFS Operational
Scenario #2: Pretty much every other model

So with this being said, and the only model in disagreement being played to its known bias, I have to say that I'm leaning more towards scenario 2.  Low placement will still be key, and the position and strength of the 50/50 low in Southeastern Canada will determine this.  Everything's heading in the right direction.  But as always the case, a storm 5 days away is not written in stone, and what you see above likely will not be exactly what happens..for better or for worse.

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