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Central PA - Winter 2020/2021


MAG5035
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3 minutes ago, Itstrainingtime said:

Welcome to the week of pissed off, non- understanding wives. My wife wanted to know what was wrong while I was watching the GFS come in...

Yes, I already got a little grief today about the ramped up, non-stop tracking. I told her that this week will make up for No real tracking last year!

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For the LSV folks:

The 00z GFS has 2-2.5” liquid jackpot, all frozen, centered around Adams, York, and Lanc counties. Beautiful deform depiction with strong omega in the DGZ. Those aren’t 10:1 ratios after dark either. 
 

The 00z CMC shows a slight different solution, but the same shellacking on the thump, then a less robust deform band (at least in the LSV), but still puts down 2”+ liquid, all snow, in those same 3 counties - York, Adams, and Lanc. 
 

Pretty remarkable. 

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Just now, AllWeather said:

I remember Jan 2016 was showing up STRONG in the guidance at 6-7 days out. By day 4-5, there was this kind of consistency and it just locked in from there. 

Yes, I remember looking at the heavy snow totals about 1 week before that historic storm. Then, the NAM got into range and started producing the crazy amounts that ended up verifying!

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12 minutes ago, AllWeather said:

For the LSV folks:

The 00z GFS has 2-2.5” liquid jackpot, all frozen, centered around Adams, York, and Lanc counties. Beautiful deform depiction with strong omega in the DGZ. Those aren’t 10:1 ratios after dark either. 
 

The 00z CMC shows a slight different solution, but the same shellacking on the thump, then a less robust deform band (at least in the LSV), but still puts down 2”+ liquid, all snow, in those same 3 counties - York, Adams, and Lanc. 
 

Pretty remarkable. 

Thrilled to have you sharing your thoughts and analysis Matt. Man, I guess it's the year we've been dealing with, but I'm weenie-ing out excessively tonight. If we ever needed this type of diversion, this is the time. 

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1 hour ago, psuhoffman said:

@MAG5035 do you know what resolution the GEFS and EPS members are run at compared to the operational?  I have noticed that the ensemble members (of both the EPS and GEFS) are often warmer even with similar or further east tracks then the operational runs.  This has been a consistent correlation for several runs across both ensemble suits.  The track of the operationals has changed but the presentation of the thermal structure of the storm has remained fairly consistent...meaning where you expect the thermal boundaries to be wrt to mslp.  But that seems to be different on the ensembles.  I am wondering if they are run at a lower resolution...they may be warmer due to not modeling the meso scale features as well.  That may not be correct...just grasping at possible causality for the observation I noted.  

Hmm, well at least on the WeatherBell products it appears the op data for the GFS and Euro is 0.25º and 0.1º respectively while their ensembles are both at 0.5º resolution. Without getting into a whole thing on GIS/mapping/degrees to meters conversion, the short answer would be yea the ensembles are run at a lower resolution (higher degree number). The high res Euro at 0.1º would be a bigger resolution difference vs it's ensemble. 

So I guess it could be implied that the lower resolution could flatten mesoscale features and thermal boundaries a bit and that difference could show with coastal low development, especially with how warm the water is off the eastern seaboard. Also, ensembles aren't going to see CAD as well as an op or especially a meso model for that same general reasoning. The higher resolution of the ops might be promoting a more explosive coastal response (and also closer to the coastline) just simply on the premise of modeling a sharper clash of warm vs cold. Given the +SST anomalies present on the eastern seaboard and a fairly respectable cold air air mass being supplied by the Canadian high, it may be wise to lean that direction with trying to blend guidance. 

Ultimately, I'm not sure how much the resolution difference actually plays in the grand scheme of things, as an ensemble is made of individual members that have their own specific conditionals to form a mean within a range of possible outcomes, which pretty much can have a similar effect as lower resolution flattening features out. Thing with ensembles is we're typically looking at them to get a handle on overall larger scale things with these events (QPF fields, pressure/height fields, accumulation probabilities, etc).. especially at this middle range where we don't have our short range or meso models in range quite yet. 

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Yes, I remember looking at the heavy snow totals about 1 week before that historic storm. Then, the NAM got into range and started producing the crazy amounts that ended up verifying!
I remember us laughing our ass of at the NAM 84 hr, then laughing as it never budged from its insane amounts, then in legit shock when all the models caved to it

Sent from my LM-X210APM using Tapatalk

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On a run to run comparison, there was a big difference in heavier snowfall placement outside of the LSV (NW of H-burg into central/northern PA) with the 0z GFS vs 18z.

1786588251_ScreenShot2020-12-12at11_58_28PM.thumb.png.a3d7c429aec30991910a3fb55901439c.png

Not really reacting too much to it as it's one run on one model, just pointing out the difference. As a whole, this is becoming more of a figuring out how much of the subforum is going to get slammed with a big snowstorm type thing. The big forecast challenge to me right now is the actual central part of the state and how much of it gets into the more excessive snowfall. I just feel even if we had the more inside scenario that gets mixing into York/Lancaster, it would be a transient issue that goes back to snow as the low deepens and moves up the coast. 

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58 minutes ago, MAG5035 said:

Hmm, well at least on the WeatherBell products it appears the op data for the GFS and Euro is 0.25º and 0.1º respectively while their ensembles are both at 0.5º resolution. Without getting into a whole thing on GIS/mapping/degrees to meters conversion, the short answer would be yea the ensembles are run at a lower resolution (higher degree number). The high res Euro at 0.1º would be a bigger resolution difference vs it's ensemble. 

So I guess it could be implied that the lower resolution could flatten mesoscale features and thermal boundaries a bit and that difference could show with coastal low development, especially with how warm the water is off the eastern seaboard. Also, ensembles aren't going to see CAD as well as an op or especially a meso model for that same general reasoning. The higher resolution of the ops might be promoting a more explosive coastal response (and also closer to the coastline) just simply on the premise of modeling a sharper clash of warm vs cold. Given the +SST anomalies present on the eastern seaboard and a fairly respectable cold air air mass being supplied by the Canadian high, it may be wise to lean that direction with trying to blend guidance. 

Ultimately, I'm not sure how much the resolution difference actually plays in the grand scheme of things, as an ensemble is made of individual members that have their own specific conditionals to form a mean within a range of possible outcomes, which pretty much can have a similar effect as lower resolution flattening features out. Thing with ensembles is we're typically looking at them to get a handle on overall larger scale things with these events (QPF fields, pressure/height fields, accumulation probabilities, etc).. especially at this middle range where we don't have our short range or meso models in range quite yet. 

Thank you 

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