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Nowcasting Thread 12/25-12/27 Storm

SEVAsNOwSTORM

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varicweather

varicweather

Posted
Posted

Wow, over running snow already entering SW VA at this time and looks to reach central VA by morning. Could this area receive 1"-3"

before the storm even gets going. Also looks like there has been some interaction between the Southern S/W and the Northern stream;

The snow in Kentucky looks as if it was enhanced by the thunderstorm activity in Texas via satellite loop:

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?wv_central_full+/24h/

Also ripples of low pressure running out along strung out cold front:

http://weather.unisys.com/index.html

Wonder when NWS posts advisories in VA? I am dreaming of a white X-mas...

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vinylfreak89

vinylfreak89

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Posted

Wow, over running snow already entering SW VA at this time and looks to reach central VA by morning. Could this area receive 1"-3"

before the storm even gets going. Also looks like there has been some interaction between the Southern S/W and the Northern stream;

The snow in Kentucky looks as if it was enhanced by the thunderstorm activity in Texas via satellite loop:

http://www.atmos.was...tral_full+/24h/

Also ripples of low pressure running out along strung out cold front:

http://weather.unisys.com/index.html

Wonder when NWS posts advisories in VA? I am dreaming of a white X-mas...

looks like there was a slight hand off with some of the southern branch energy based on that satellite loop... probably why we saw the southern shortwave open for a bit and elongate.

On another note, assuming the west trends verify, there's only one thing keeping this from being historic DC-PHI... the WAA gets cut off as the storm gets going and we get nealy all our precip from the CCB. I believe this is due to the placement of the two main shortwaves when the phasing occurs which causes the low level jet to basically die out when it hits the VA/NC border as a small 850 low closes off in SE PA... this is evidenced by the very light winds at 850 and 700 on the 00Z GFS.

already some minor errors on the 00Z GFS. the TX shortwave is too far SW by about 30 miles. also the IA shortwave is quite a bit stronger and the whole trough is a bit deeper than the 00z GFS. The NAM actually is doing a much better job with the 6 hr forecast, and while not focusing on the finer details of the NAM, the overall 500 mb pattern was better than the 00Z GFS with a slightly deeper and sharper trough. It also accomplished more of a true phase, with the southern shortwave being pulled back in to the base of the trough, rather than shearing out and the northern shortwave "catching it" (which is why my earlier point occurs). The main issue with the NAM is the convective feedback that causes energy to be displaced out front.

The RUC since 00Z is slowly trending away from the formation of the initial 850 low and keeping the low level jet stronger though still just S of DC... if we see this trend continue, this could easily become historic for the mid atlantic as well... having the usual warm air advection snows would up our amounts by at least 3-4" and with the more true phase, there will be less of a need for the storm to "hook" in which will put us down here in the heavy snow band for longer.

This is all a moot point by time you get to NYC and north as the storm is plenty consolidating by time it reaches NJ... this only has an affect from SW NJ town to the northern neck of VA... south and north of there this has no bearing. Note that no matter what happens, it is very likely NYC on north will see higher QPF than areas to the SW... but likely also with less dynamics as the storm occludes.

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varicweather

varicweather

Posted
Posted

looks like there was a slight hand off with some of the southern branch energy based on that satellite loop... probably why we saw the southern shortwave open for a bit and elongate.

On another note, assuming the west trends verify, there's only one thing keeping this from being historic DC-PHI... the WAA gets cut off as the storm gets going and we get nealy all our precip from the CCB. I believe this is due to the placement of the two main shortwaves when the phasing occurs which causes the low level jet to basically die out when it hits the VA/NC border as a small 850 low closes off in SE PA... this is evidenced by the very light winds at 850 and 700 on the 00Z GFS.

already some minor errors on the 00Z GFS. the TX shortwave is too far SW by about 30 miles. also the IA shortwave is quite a bit stronger and the whole trough is a bit deeper than the 00z GFS. The NAM actually is doing a much better job with the 6 hr forecast, and while not focusing on the finer details of the NAM, the overall 500 mb pattern was better than the 00Z GFS with a slightly deeper and sharper trough. It also accomplished more of a true phase, with the southern shortwave being pulled back in to the base of the trough, rather than shearing out and the northern shortwave "catching it" (which is why my earlier point occurs). The main issue with the NAM is the convective feedback that causes energy to be displaced out front.

The RUC since 00Z is slowly trending away from the formation of the initial 850 low and keeping the low level jet stronger though still just S of DC... if we see this trend continue, this could easily become historic for the mid atlantic as well... having the usual warm air advection snows would up our amounts by at least 3-4" and with the more true phase, there will be less of a need for the storm to "hook" in which will put us down here in the heavy snow band for longer.

This is all a moot point by time you get to NYC and north as the storm is plenty consolidating by time it reaches NJ... this only has an affect from SW NJ town to the northern neck of VA... south and north of there this has no bearing. Note that no matter what happens, it is very likely NYC on north will see higher QPF than areas to the SW... but likely also with less dynamics as the storm occludes.

Enjoyed the analysis. I agree the trough does seem to be deeper as it looks like the beginning stages of the phase are taking place. I like

how the base of the trough is coming in behind the shortwave. I would like to see more moisture break out ahead of the storm, but I

suppose this will happen in time.The s/w is also leaving a wake of dry air behind it on the water vapor loop acting as a snow plow pushing

up the warm, moist air (lift).

http://www.rap.ucar.edu/weather/satellite/displaySat.php?region=US&itype=wv&size=large&endDate=20101224&endTime=-1&duration=6

MERRY X-MAS to ya and to all!

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Stormpc

Stormpc

Posted
Posted

to me the water vapor presentation looks spectacular... i have slight concerns about the radar....heading a bit too ENE for my liking right now but might be starting to see the pivot in the last hour or so

Looks like the UL diving down is beginning to interact and start the pivot trend, to my eye.

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psuhoffman

psuhoffman

Posted
Posted

to me the water vapor presentation looks spectacular... i have slight concerns about the radar....heading a bit too ENE for my liking right now but might be starting to see the pivot in the last hour or so

you're going to have a LONG day if you are radar watching, guidance suggests that band continues to slide mostly east until tonight when the h5 low starts to cut off and the flow really backs. Then everything takes a left hook and heads due north, but before that there is a point where everything will be along the Carolina coast and appear to be heading OTS. Look at a loop of the radar from the January 2000 storm and how far east everything got before turning north. This is a very similar track.

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Reale WX

Reale WX

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you're going to have a LONG day if you are radar watching, guidance suggests that band continues to slide mostly east until tonight when the h5 low starts to cut off and the flow really backs. Then everything takes a left hook and heads due north, but before that there is a point where everything will be along the Carolina coast and appear to be heading OTS. Look at a loop of the radar from the January 2000 storm and how far east everything got before turning north. This is a very similar track.

ha yeah it went all the way into the panhandle before turning north

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PhineasC

PhineasC

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Posted

you're going to have a LONG day if you are radar watching, guidance suggests that band continues to slide mostly east until tonight when the h5 low starts to cut off and the flow really backs. Then everything takes a left hook and heads due north, but before that there is a point where everything will be along the Carolina coast and appear to be heading OTS. Look at a loop of the radar from the January 2000 storm and how far east everything got before turning north. This is a very similar track.

vinylfreak is an OCD weenie. He will be here all day and night worrying himself to death.

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vinylfreak89

vinylfreak89

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Posted

you're going to have a LONG day if you are radar watching, guidance suggests that band continues to slide mostly east until tonight when the h5 low starts to cut off and the flow really backs. Then everything takes a left hook and heads due north, but before that there is a point where everything will be along the Carolina coast and appear to be heading OTS. Look at a loop of the radar from the January 2000 storm and how far east everything got before turning north. This is a very similar track.

errr I'm not watching radar because I"m concerned about the overall storm.... I think 6-12 is a good bet for DC. I'm more interested on what goes on on the front end.... that will be the difference between this being major and historic.... my point is if the pivot happens sooner, there will be no need for "backing" and we can stay in the heavier precip longer... hence more accumulation.

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Jebman

Jebman

Posted
Posted

you're going to have a LONG day if you are radar watching, guidance suggests that band continues to slide mostly east until tonight when the h5 low starts to cut off and the flow really backs. Then everything takes a left hook and heads due north, but before that there is a point where everything will be along the Carolina coast and appear to be heading OTS. Look at a loop of the radar from the January 2000 storm and how far east everything got before turning north. This is a very similar track.

Gonna be a lot of weenies panicking over that apparent OTS trend until the hook and pcpn trends northward.

Also going to be a LOT of blowing/drifting of the snow as winds kick up all over Sunday night thru Tuesday. Many a driveway will have to be shoveled numerous times as the powdery snow keeps drifting 'em shut. Sucks to be us lol

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Jebman

Jebman

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vinylfreak is an OCD weenie. He will be here all day and night worrying himself to death.

Excellent analysis - That is what makes a good snowstorm great. I'll be putting on my own OCD program - meticulously recording every scrap of these analyses onto my own board and onto other media.

I will NEVER, EVER be "Easterned" again. Every radar picture, every analysis will be meticulously saved. I've been bitten by the snow bug pathologically badly. There is no cure - except to throw my sorry ass out into the Alaskan wilderness in -135 degree weather in 100 mph winds and in 79 feet of snow with a full on blizzard blowing, Bear Grylls style.I have already gotten a full treatment of DT's performance about the pooch and that epic picture of him in bed with the big dog.

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