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Feb. 18-20, 2012 Disco/Analysis


Poimen

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This system is exciting me no doubt. Reminds me a lot of the December 19 2009 system. I think Allan mentioned this yesterday. The most important feature IMO, when examining the models is the cutoff low forming over the northeast later this week. Once that forms, the stronger/further south it is, the colder this system will be.As of now it appears just strong enough to keep this system on the coastline perhaps a bit offshore. Of course the question of phasing will also be in play as to what happens with this as it heads offshore into the atlantic. I think if you live in central/east NC you want as little phasing as possible, b/c a track from the southern deep south up the coastline is not a good climo track east I77.

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Boy the NAM just doesn't want to move that energy out west much but it looks potent that's for sure at 84 on the 12z NAM

Hmmm. I wonder what Robert's (Foothills) thoughts are concerning the overall timing of the vort. It seems as though as its slowing down there is more separation between systems allowing it to retain it's strength. Robert discussed a few times this year how many anomalous deep south ULL's have come through the SE this year. It's the 84HR NAM, but still something to look for on the coming runs of the globals.

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Hmmm. I wonder what Robert's (Foothills) thoughts are concerning the overall timing of the vort. It seems as though as its slowing down there is more separation between systems allowing it to retain it's strength. Robert discussed a few times this year how many anomalous deep south ULL's have come through the SE this year. It's the 84HR NAM, but still something to look for on the coming runs of the globals.

FWIW the 6z dgex did not bring the system in until Monday.

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It is all about timing as others have stated. Players include the Great Lakes shortwave (GL s/w) and the upstream Pac-NW trough. The latter will influence the all important timing (and perhaps strength) of the system of interest kicking out of Texas. Simple explanation of the 00/06Z GFS differences is just timing. The 00Z was the first GFS run to show a Euro-like solution with our Texas system kicking with/ahead of the GL s/w. Perhaps the 12Z GFS and subsequent runs will go back to the Euro, but one can't just throw out the 06Z as rubbish. This far out it is perfectly acceptable for a human or a computer to be forecasting the Texas system behind the GL s/w which is what the 06Z does. That puts our system in subsidence behind the jet streak associated with the GL s/w. Short wave ridging is another way to put it. The 00Z GFS and Euro have our Texas system coming out with/ahead of the GL s/w which is at least neutral. if slightly ahead that puts our Texas system in ascent ahead of the GL s/w and also gives the system a slight negative tilt. All are fine and good, but not if the 06Z GFS is correct. Remember the GFS had been consistently like the 06Z in prior runs except the 00Z.

I'd wait for the timing issue to work out before even addressing cold air. Maybe when our system is completely onshore today? Of course "better" timing would also generate a little local dynamic cooling with better lift, but not enough to overcome issues in the boundary layer elsewhere. Unfortunately NC may be hosed outside the mountains. Piedmont is not even looking that good with the sfc high back over the Midwest. I don't see a way to deliver cold air east of the Apps. Of course the mountains would do well. Cold air supply may be there for lower elevations of northeast Tennessee, but middle Tenn prolly misses out on best QPF. Looks like another typical Southern forecast (2010 was an exception): When in doubt between rain and snow just go rain.

Totally different story in the mountains, regarding cold air, but even the mountains need the better timing. If the system comes together, timing and interaction with the GL s/w, the mountains will be set. :ski:

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The 00Z was the first GFS run to show a Euro-like solution with our Texas system kicking with/ahead of the GL s/w. Perhaps the 12Z GFS and subsequent runs will go back to the Euro, but one can't just throw out the 06Z as rubbish. This far out it is perfectly acceptable for a human or a computer to be forecasting the Texas system behind the GL s/w which is what the 06Z does. That puts our system in subsidence behind the jet streak associated with the GL s/w. Short wave ridging is another way to put it. The 00Z GFS and Euro have our Texas system coming out with/ahead of the GL s/w which is at least neutral. if slightly ahead that puts our Texas system in ascent ahead of the GL s/w and also gives the system a slight negative tilt. All are fine and good, but not if the 06Z GFS is correct. Remember the GFS had been consistently like the 06Z in prior runs except the 00Z.

That's funny, I want to see the shortwaves and troughiness in the Great Lakes get out of there and into the NE prior to our southwest wave kicking east, for a colder setup. More like the UKMet and NAM look.

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It is all about timing as others have stated. Players include the Great Lakes shortwave (GL s/w) and the upstream Pac-NW trough. The latter will influence the all important timing (and perhaps strength) of the system of interest kicking out of Texas. Simple explanation of the 00/06Z GFS differences is just timing. The 00Z was the first GFS run to show a Euro-like solution with our Texas system kicking with/ahead of the GL s/w. Perhaps the 12Z GFS and subsequent runs will go back to the Euro, but one can't just throw out the 06Z as rubbish. This far out it is perfectly acceptable for a human or a computer to be forecasting the Texas system behind the GL s/w which is what the 06Z does. That puts our system in subsidence behind the jet streak associated with the GL s/w. Short wave ridging is another way to put it. The 00Z GFS and Euro have our Texas system coming out with/ahead of the GL s/w which is at least neutral. if slightly ahead that puts our Texas system in ascent ahead of the GL s/w and also gives the system a slight negative tilt. All are fine and good, but not if the 06Z GFS is correct. Remember the GFS had been consistently like the 06Z in prior runs except the 00Z.

I'd wait for the timing issue to work out before even addressing cold air. Maybe when our system is completely onshore today? Of course "better" timing would also generate a little local dynamic cooling with better lift, but not enough to overcome issues in the boundary layer elsewhere. Unfortunately NC may be hosed outside the mountains. Piedmont is not even looking that good with the sfc high back over the Midwest. I don't see a way to deliver cold air east of the Apps. Of course the mountains would do well. Cold air supply may be there for lower elevations of northeast Tennessee, but middle Tenn prolly misses out on best QPF. Looks like another typical Southern forecast (2010 was an exception): When in doubt between rain and snow just go rain.

Totally different story in the mountains, regarding cold air, but even the mountains need the better timing. If the system comes together, timing and interaction with the GL s/w, the mountains will be set. :ski:

Wow, didn't want to hear that. Can't say I'm surprised though. Even yesterday's 12Z EURO surface temps looked too warm for good accumulation even though it showed snow verbatim. If I don't see a colder trend today I think I'll move on. EURO monthlies said something about not this weekend but next weekend; 2/25. I wonder if that will produce. :cry:

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Wow, didn't want to hear that. Can't say I'm surprised though. Even yesterday's 12Z EURO surface temps looked too warm for good accumulation even though it showed snow verbatim. If I don't see a colder trend today I think I'll move on. EURO monthlies said something about not this weekend but next weekend; 2/25. I wonder if that will produce. :cry:

Not sure why anyone would throw the towel in on this until around Friday or so. Still plenty of time for lots of things to happen. As others who are experts on our area have stated it could come down to some dynamic cooling and a little help with a sfc high. nrg could very well be right, but as he is just giving his opinion on what he thinks is a likely scenario. Let's see where the 12z is on Thursday before doing any cliff diving.

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This system is exciting me no doubt. Reminds me a lot of the December 19 2009 system. I think Allan mentioned this yesterday. The most important feature IMO, when examining the models is the cutoff low forming over the northeast later this week. Once that forms, the stronger/further south it is, the colder this system will be.As of now it appears just strong enough to keep this system on the coastline perhaps a bit offshore. Of course the question of phasing will also be in play as to what happens with this as it heads offshore into the atlantic. I think if you live in central/east NC you want as little phasing as possible, b/c a track from the southern deep south up the coastline is not a good climo track east I77.

Brandon,Forgive a uneducated question. Most of that storm was on the 18th here & we got 18" with a couple of hours of thundersnow. Our area looked like a war zone with downed trees and abandoned cars. We lost our power for 54 hrs. Are the dynamics looking the same or is it the track? Loved the snowfall total with that storm but I could do without the rest. Thanks Don

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0Z EMCWF:

NC: Limited to NC Mountains

VA: Good snow statewide down to near the NC Border with a sharp cutoff in southern VA

6z GFS

Nothing for anyone

6z DGEX:

NC: West of I-77/I-40 similar to the December 19 2009 Big Snow

VA: Western VA

Forgetting the 00z GFS last night which was snow for Central and northern NC into VA...and the 12z run of the Euro yesterday which was snow for many in NC.

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It is all about timing as others have stated. Players include the Great Lakes shortwave (GL s/w) and the upstream Pac-NW trough. The latter will influence the all important timing (and perhaps strength) of the system of interest kicking out of Texas. Simple explanation of the 00/06Z GFS differences is just timing. The 00Z was the first GFS run to show a Euro-like solution with our Texas system kicking with/ahead of the GL s/w. Perhaps the 12Z GFS and subsequent runs will go back to the Euro, but one can't just throw out the 06Z as rubbish. This far out it is perfectly acceptable for a human or a computer to be forecasting the Texas system behind the GL s/w which is what the 06Z does. That puts our system in subsidence behind the jet streak associated with the GL s/w. Short wave ridging is another way to put it. The 00Z GFS and Euro have our Texas system coming out with/ahead of the GL s/w which is at least neutral. if slightly ahead that puts our Texas system in ascent ahead of the GL s/w and also gives the system a slight negative tilt. All are fine and good, but not if the 06Z GFS is correct. Remember the GFS had been consistently like the 06Z in prior runs except the 00Z.

I'd wait for the timing issue to work out before even addressing cold air. Maybe when our system is completely onshore today? Of course "better" timing would also generate a little local dynamic cooling with better lift, but not enough to overcome issues in the boundary layer elsewhere. Unfortunately NC may be hosed outside the mountains. Piedmont is not even looking that good with the sfc high back over the Midwest. I don't see a way to deliver cold air east of the Apps. Of course the mountains would do well. Cold air supply may be there for lower elevations of northeast Tennessee, but middle Tenn prolly misses out on best QPF. Looks like another typical Southern forecast (2010 was an exception): When in doubt between rain and snow just go rain.

Totally different story in the mountains, regarding cold air, but even the mountains need the better timing. If the system comes together, timing and interaction with the GL s/w, the mountains will be set. :ski:

I've not fully analyzed anything yet because I'm of the belief that it's just silly to start fervently looking at every model run past 120 hours, but the large scale synoptic pattern supports what nrgjeff is saying here regarding the lack of a significant surface high. However, we do know that the ECMWF has a tendency to over-phase systems, so I actually thought what the 00z GFS showed last night was pretty reasonable. The question is which solution will win out? It's quite possible the ECMWF will undergo significant changes in the coming runs (probably to a less phased solution), but that's not to say it won't eventually come back to it's 00z solution. Once I get into the office today, I plan to really analyze the 12z model suite and I'll offer my full impressions then.

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I've not fully analyzed anything yet because I'm of the belief that it's just silly to start fervently looking at every model run past 120 hours, but the large scale synoptic pattern supports what nrgjeff is saying here regarding the lack of a significant surface high. However, we do know that the ECMWF has a tendency to over-phase systems, so I actually thought what the 00z GFS showed last night was pretty reasonable. The question is which solution will win out? It's quite possible the ECMWF will undergo significant changes in the coming runs (probably to a less phased solution), but that's not to say it won't eventually come back to it's 00z solution. Once I get into the office today, I plan to really analyze the 12z model suite and I'll offer my full impressions then.

We look forward to hearing your thoughts.

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Couple quick observations before the gfs rolls. The 6z op was a warm outlier compared to the ensemble suite. Also flatter with the wave than almost all the members. Several with good looks for NC, several not. Only counted two with a surface wave near the great lakes, most had high pressure setting up shop in the oh valley, several with a tap into central Canada building the high into the 1030 range as the system departs around 150.

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Couple quick observations before the gfs rolls. The 6z op was a warm outlier compared to the ensemble suite. Also flatter with the wave than almost all the members. Several with good looks for NC, several not. Only counted two with a surface wave near the great lakes, most had high pressure setting up shop in the oh valley, several with a tap into central Canada building the high into the 1030 range as the system departs around 150.

A met in NE said last night he felt we may start seeing a high pressure signal show up over the lakes with the way the ensembles have been trending

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Just comparing the 5h to 0z run it looks relatively close, the southern SW is taking a beating, really weakening, curious to see if this completely get's dampened out.

With that energy not as strong to our west, I would think this should be a lot better than the 6z...probably a colder solution with less moisture.

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