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February 8-12 model Discussion II


Isopycnic

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Folks,

The 18Z NAM gives ATL-AHN a major snow on Wed. night/Thu. morning of ~4" from ~0.35 (north)-0.40" (Tony's abode) of qpf. This makes it the 4th straight run giving them a sig. snow. Bring it on!

For ATL/AHN's sake, I hope there never is a strong surface low as this is close to the best case scenario. Otherwise, we'd likely have to worry about it being too warm from a too far north track.

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Care to explain or post some pictures for the visual learners? Thanks!

The trailing 500mb vort max acts to keep light precip going as you get closer to the SE coast, rather than the precip just zipping out to sea. Probably won't amount to much, but it could mean some areas closer to the coast have a shot at seeing some flakes as the precip winds down.

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Folks,

The 18Z NAM gives ATL-AHN a major snow on Wed. night/Thu. morning of ~4" from ~0.35 (north)-0.40" (Tony's abode) of qpf. This makes it the 4th straight run giving them a sig. snow. Bring it on!

For ATL/AHN's sake, I hope there never is a strong surface low as this is close to the best case scenario. Otherwise, we'd likely have to worry about it being too warm from a too far north track.

You seem a lot more excited over this one than the last one, are you going to be back up here instead of savannah?

Nam is a little drier than the last run for north ga but it has more to do with it being slightly further south than anything I think.

For fun, let's just assume the nam is right and we get 0.35 to 0.40. Most, if not all, of the snow falls in a 6 hour window, so there would be some respectable rates for a few hours. But after it's over, it will melt thursday just about as fast as it fell. Nam has temps in the 40 to 45 degree range thursday afternoon. On top of that, both the nam/gfs keep my area above freezing until just a few hours before sunrise friday. So I'd be surprised if there is much left by friday. Now this fits the definition of a southern snow..falls and melts within the same 24 hours. :axe:

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18z NAM -- 5h maps looked better, surface looked worse.

That's why they call it the 18z NAM.

I think the problem with this run is that piece of energy rounding the Polar vortex is much further south on this run and thus leaves less room for our shortwave. Compare 12z to 18z with respect to the vorticity around the great lakes area and you will see what what I mean.

We need all that crap up there to stay farther north.

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You seem a lot more excited over this one than the last one, are you going to be back up here instead of savannah?

Nam is a little drier than the last run for north ga but it has more to do with it being slightly further south than anything I think.

For fun, let's just assume the nam is right and we get 0.35 to 0.40. Most, if not all, of the snow falls in a 6 hour window, so there would be some respectable rates for a few hours. But after it's over, it will melt thursday just about as fast as it fell. Nam has temps in the 40 to 45 degree range thursday afternoon. On top of that, both the nam/gfs keep my area above freezing until just a few hours before sunrise friday. So I'd be surprised if there is much left by friday. Now this fits the definition of a southern snow..falls and melts within the same 24 hours. :axe:

I'd say that scenario would be very nice this time. The January snow cost us a pretty penny at my company (down time). Low impact, high aesthetics!

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Folks,

The 18Z NAM gives ATL-AHN a major snow on Wed. night/Thu. morning of ~4" from ~0.35 (north)-0.40" (Tony's abode) of qpf. This makes it the 4th straight run giving them a sig. snow. Bring it on!

For ATL/AHN's sake, I hope there never is a strong surface low as this is close to the best case scenario. Otherwise, we'd likely have to worry about it being too warm from a too far north track.

Okay, I have to ask. Do you live in Atlanta or Athens? Just wondering because I've yet to see a post of yours without the phrase "ATL-AHN" in it.

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I think the problem with this run is that piece of energy rounding the Polar vortex is much further south on this run and thus leaves less room for our shortwave. Compare 12z to 18z with respect to the vorticity around the great lakes area and you will see what what I mean.

We need all that crap up there to stay farther north.

Yeah, we should be paying just as much attention to that parcel over the Great Lakes. Get that out of the way a little more and get our southern wave a little stronger, and that can lead to more QPF. It's a fine line though. A few days ago we were worried about too little blocking with the Polar Vortex and an apps runner.

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My car really needs washed but I've been putting it off because of the "snow potential". Now that it looks like northern NC won't be in on any action, I think I'll wash it. That usually guarantees a change in the forecast....so how about all you northern North Carolinians get out there and wash your car today or tomorrow! :thumbsup:

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FFC:

BIG QUESTION CONCERNING THE SHORT TERM FORECAST PERIOD REMAINS THE

WINTER WEATHER POTENTIAL FOR LATE WEDNESDAY. ECMWF...AND MORE SO THE

GFS... CONTINUE TO TREND FARTHER SOUTH AND SOMEWHAT WEAK WITH THE

SURFACE LOW DEVELOPMENT WITH THIS SYSTEM. FAST MOVING SHORT WAVE IS

CORRESPONDINGLY WEAK. TIMING STILL APPEARS TO BE CONCENTRATED ON

WEDNESDAY NIGHT INTO EARLY THURSDAY...AND THICKNESS VALUES CONTINUE

TO SUPPORT A MOSTLY SNOW EVENT FOR NORTH GEORGIA...BUT THERE IS STILL

QUITE A BIT OF UNCERTAINTY CONCERNING AMOUNTS. WITH THE RELATIVELY

WEAK AND MORE SOUTHERLY TRACKING SURFACE LOW...QPF AMOUNTS FOR NORTH

GEORGIA CONTINUE TO REMAIN FAIRLY LOW. I WILL BE ISSUING ANOTHER

SPECIAL WEATHER STATEMENT TO ADDRESS THIS SYSTEM...BUT HOLD OFF ON

ANY WATCHES AT THIS TIME.

Suprised they were considering a watch already. Pretty impressive for them IMO...

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You seem a lot more excited over this one than the last one, are you going to be back up here instead of savannah?

I doubt it. If there were a feasible way I could take a quick trip there, I'd do it as I've missed the Xmas and Jan. snows due to being in Sav. As of now, I'd say I won't be there. One of the reasons for the excitement even without being there is that it is so exciting from a climo point of view and it tells me that we may be into a new era of more frequent snows (due to the sun/volcanoes/colder Pacific??) similar to the late 1800's/early 1900's. IF so, that would bode well for the next couple of decades. Another reason for the excitement: I have a sis there and some friends there who ask me to forecast for them. I surely "picked" the wrong winter to be in Savannah the entire time, but in reality had no choice.

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I think the problem lies in the GFS OP bias and IMO major failing in shearing waves as they move west to east. Does it every time. Hence, the vort is weaker than any other model and does much less than any other model. Yes, the wave will weaken as it moves west to east. But will it just disappear? Just amazing though to see it still @ the 48-60 hour window.

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