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February 8-12 model Discussion II


Isopycnic

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It is also the NAM, which has been inconsistent and wrong for most of this winter. Based on these trends, I expect ECMWF 12z to be similar to 0z this morning and for the GFS to hint at a stronger system by today or early tomorrow morning.

Climo is on our side. Plus, if the cold air actually makes its way south as the GFS and Euro hinted a couple of days ago, that should be enough to provide a stronger system and higher QPF values. This is a very interesting storm. Storm #1 on Monday/Tuesday will likely set us up for this possible winter storm. Let's see how the models handle #1 and then we'll have a better idea about the setup of this upcoming system.

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It's the 84 hour NAM. Throw it out! Come on guys, you know how this works by now. :D

Not so fast. Last nights 96 hour ECMWF and todays 84 NAM are dead ringers. Match almost perfectly. If the Lakes wave can stay "not so diggy" then the Texas wave will be further north than shown. I'm undecided on this. Usually the Euro is too amplified on northern streams, so that argues for the Lakes s/w to not affect the southern one too much other than prevent a jump too far north. But if its even stronger than shown , then the Texas system will skirt mostly just south of of I-40 and maybe much of eastern Tn/w NC areas, before just hooking up the NC coast, much like the Euro was showing. That would benefit areas in Miss, Ala, Ga and SC a good deal. Only time will tell. There's a couple more s/w in the flow behind it that weren't there so that argues agains't an amplified system, however the lead system could still drop over .50 to .75" amounts qpf north of its track , and atually be enhanced precip thanks to the Lakes system offering more converegence on its north side, which then would actually benefit TN and NC (the northern side of the system). But so much would have to be timed perfectly and track just right. Way too far out yet to say for sure how this goes.

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For ATL-AHN's best shot at a sig. snow (say 2"+), I'd want a weak low as I don't think that area can afford a too wound up low as there's little room and would very likely mean a too far north track/too much warming. Climo largely agrees with this. A too wound up low is probably the enemy not the friend if you want snow there. So, think weak and supressed.

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Oh let me get one thing straight, I thought the 12z NAM was a step in the right direction compared to last night.

Sorry dude. I should have read the prior page. I thought folks were under the impression it was no good. If it's showing a better solution, then we should keep it, obviously. :). I'm just playing around anyway.

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Not so fast. Last nights 96 hour ECMWF and todays 84 NAM are dead ringers. Match almost perfectly. If the Lakes wave can stay "not so diggy" then the Texas wave will be further north than shown. I'm undecided on this. Usually the Euro is too amplified on northern streams, so that argues for the Lakes s/w to not affect the southern one too much other than prevent a jump too far north. But if its even stronger than shown , then the Texas system will skirt mostly just south of of I-40 and maybe much of eastern Tn/w NC areas, before just hooking up the NC coast, much like the Euro was showing. That would benefit areas in Miss, Ala, Ga and SC a good deal. Only time will tell. There's a couple more s/w in the flow behind it that weren't there so that argues agains't an amplified system, however the lead system could still drop over .50 to .75" amounts qpf north of its track , and atually be enhanced precip thanks to the Lakes system offering more converegence on its north side, which then would actually benefit TN and NC (the northern side of the system). But so much would have to be timed perfectly and track just right. Way too far out yet to say for sure how this goes.

[attachment=17217:Geopotential3250032hPa32an

Great post. I was just kidding with my previous post. Your post explains things nicely.

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More 12z gfs: Some snow E NC...2-3' Otherwise, largely storm cancel due to it being too weak. I still want supression for ATL-AHN's sake, but this run won't give snow of consequence to anyone outside of E NC.

See you folks at the 12Z Euro!

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The GFS is good for everyone with the eastern Canada vortex. And at 84 and 96 it doesn't allow the Lakes s/w to mess with the southern system so thats good (it gets pulled east due to the strong Eastern Can system) But whats wrong is the next s/w diving into the Rockies. The Euro had that as well, so now they're both weakening the southern system but for different reason's probably. It willtake the Euro to resolve this. On the one hand its good if we get the Lakes system to pull east toward New England , on the other hand we need a strong consolidated southern system and not much of anything behind it

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@93 the GFS is still suppression city and it's killing us on the transfer. If you believe the trends not bad right now.

The fact the the GFS is super suppressed might be a good thing, but the other models have been trending this direction as well. I think its important to think of the reason why though. It looks to me like the models are really keying in on the S/W diving south behind our storm, which is really killing our storm along with the suppressive affects of the vortex in Canada. I dont like the fact that the models have been showing this trailing shortwave stronger because we could potentially end up with no storm at all, which the 12z GFS is very close to showing already...

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The fact the the GFS is super suppressed might be a good thing, but the other models have been trending this direction as well. I think its important to think of the reason why though. It looks to me like the models are really keying in on the S/W diving south behind our storm, which is really killing our storm along with the suppressive affects of the vortex in Canada. I dont like the fact that the models have been showing this trailing shortwave stronger because we could potentially end up with no storm at all, which the 12z GFS is very close to showing already...

From a snow disappointment angle, I'd rather have no storm at all than a strong storm that gives no wintry precip. to the ATL-AHN area because it is too far north/too warm at 850 mb. OTOH, there are other exciting things to watch for like IP/ZR and good drought busting rains even if no snow.

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The one thing that does look worrisome though are these sfc temps that have been trending warmer....but is that just because of the lack of moisture?

I wouldn't worry about temps until the Texas system gets much stronger than shown. For us to get accum. snow, we need that system to be much stronger than shown to allow some moisture and lift our way. The next system in the Rockies is probably de-amplifying the lead wave. It will take the Euro to resolve it. The one good bit of info, if youre hunting for snow here, is that the Lakes system doesn't act as too much of a supressor like the Euro was showing, and I bet it starts to follow the GFS lead in that regard. So far, still looks like a decent snow for Ok,Ark and probably western TN and northern Ms. before things start falling apart, which may or may not happen.

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The one thing that does look worrisome though are these sfc temps that have been trending warmer....but is that just because of the lack of moisture?

Yes. Not as much cooling without moisture. We've seen the GFS do this many times this year. Only if the Euro starts to show it getting sheared will I be worried as it keeps just enough separation between systems.

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You can see how the GFS just loses it after 84. At 84, it looks like a good setup. An 850 low is forming in n. LA and the s/w is strong and healthy, then it disintegrates shortly thereafter. May or may not be true. Also, the fact teh PNA out west is starting to break down around this time will have a huge impact on the amp. of this southern system. Its all about the timing of things around it. The Euro may actually hold this Texas system strong through the Southeast, which would be a pretty big impact Winter storm, and then it dies out and not goes up the coast, thanks to the timing on the decay of the PNA out west. I don't really see a lakes cutter or Apps runner threat for those reasons.

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You can see how the GFS just loses it after 84. At 84, it looks like a good setup. An 850 low is forming in n. LA and the s/w is strong and healthy, then it disintegrates shortly thereafter. May or may not be true. Also, the fact teh PNA out west is starting to break down around this time will have a huge impact on the amp. of this southern system. Its all about the timing of things around it. The Euro may actually hold this Texas system strong through the Southeast, which would be a pretty big impact Winter storm, and then it dies out and not goes up the coast, thanks to the timing on the decay of the PNA out west. I don't really see a lakes cutter or Apps runner threat for those reasons.

hasn't it been a model bias to dampen out the s/w too soon?

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hasn't it been a model bias to dampen out the s/w too soon?

maybe in the past, but this is different from our other storms this season where there was a strong ULL. This one is based on a northern stream dropping south because of PNA ridging, and that ridging on most models is shown to start flattening around the time the s/w is in Tex/La area...so its a timing issue of when it flattens. Its nothng for the models to be off a few hours to cople of days on that, so that means all the difference in the world here as it either means no storm, weak moisture or even a much bigger one if they're wrong on that PNA out west. Lots of complicated factors have to come right here like always.

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From a snow disappointment angle, I'd rather have no storm at all than a strong storm that gives no wintry precip. to the ATL-AHN area because it is too far north/too warm at 850 mb. OTOH, there are other exciting things to watch for like IP/ZR and good drought busting rains even if no snow.

I think i'll pass on the rain. We've had enough rain the past week to last 2 months. Lakes are full, so I doubt we're in a drought.

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maybe in the past, but this is different from our other storms this season where there was a strong ULL. This one is based on a northern stream dropping south because of PNA ridging, and that ridging on most models is shown to start flattening around the time the s/w is in Tex/La area...so its a timing issue of when it flattens. Its nothng for the models to be off a few hours to cople of days on that, so that means all the difference in the world here as it either means no storm, weak moisture or even a much bigger one if they're wrong on that PNA out west. Lots of complicated factors have to come right here like always.

Oh ok thanks hopefully that ridge stays strong :arrowhead:

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The threat of a too strong system bringing rain diminishes with each model run- that seems the least likely scenario. I am guessing te GFS weakens the short wave to much- which would meant at least a couple of inches for some folks, maybe more. Probably not a massive snow for anyone either. Hopefully the GFS and CMC hold the line on heavier precip.

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I don't see this system being more than a few flurries for western half of NC maybe even rain showers at this rate. Temps are trending warmer and warmer before, during, and after the storm. Just don't see anything to get this storm going qpf wise or even temp wise. Sorry folks maybe late Feb or early March we may get a little something

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I don't see this system being more than a few flurries for western half of NC maybe even rain showers at this rate. Temps are trending warmer and warmer before, during, and after the storm. Just don't see anything to get this storm going qpf wise or even temp wise. Sorry folks maybe late Feb or early March we may get a little something

Certainly a complete screw is possible but saying this given what the Euro and CMC showed last night is being too pessimistic IMO. Lets wait for at least a few more runs before commencing the Brick-style gloom and doom,

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