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Friday, January 21st Storm Discussion II


Baroclinic Zone

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GFS seems to really like ORH through ne mass where ccb hangs for a couple of more hours.

Its amazing how quickly we've trended into a nice a little ccb, at this time yesterday it was looking like a quick shot of WAA with very little moisture actually being circulated into it via cold conveyor processes.

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Its amazing how quickly we've trended into a nice a little ccb, at this time yesterday it was looking like a quick shot of WAA with very little moisture actually being circulated into it via cold conveyor processes.

It just took a further south vortmax and a quick developing low. That's what we were talking about yesterday.

It does kind of make sense. I understand the whole 500 pattern and how it looked ugly, but the low seemed very displaced from the vortmax. Also, no big high to the north to force any WAA well to the south. Without that, WAA could take place further nw, and thus enhance baroclinicity further nw.

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It just took a further south vortmax and a quick developing low. That's what we were talking about yesterday.

It does kind of make sense. I understand the whole 500 pattern and how it looked ugly, but the low seemed very displaced from the vortmax. Also, no big high to the north to force any WAA well to the south. Without that, WAA could take place further nw, and thus enhance baroclinicity further nw.

It was good to get a little more southern stream involved too, that probably enhances all those processes. A little more initial moisture to work with as well instead of trying to start from scratch with only Atlantic moisture trying to revive a fairly dry system....its already got some juice to it coming out of the OH Valley. Probably helps pump up ridge in front of it...sort of a lot of positive feedback processes in this particular setup.

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I am speachless with the GFS, completely just made my day. I should crack a beer open during lunch time to celebrate.

I was expecting a nudge to the north from yesterday's 12z runs, but this is exceeding that expectation. I'm still keeping that 3 or 4" mby prediction pending the foreigners but I'm leaning pretty hard towards 6-10.

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Definitely expect warnings to go up for much of the region based on 12Z models and statements from the recent forecast discussion by BOX

WE ARE NOT READY TO COMPLETELY JUMP ON THE NAM AS THIS STILLREMAINS AN OPEN WAVE AT 850/700 MB WHICH WILL RESULT INPROGRESSIVE SYSTEM WITH LIMITED DURATION OF HEAVY BANDED SNOWHOWEVER...THERE ARE STRONG SIGNALS FOR A BRIEF PERIOD OF HEAVYSNOW AROUND 12Z WITH EXCELLENT SNOW GROWTH OMEGA AND CROSSSECTIONS INDICATING -EPV ABOVE MODEST LOW/MID LEVEL FRONTOGENESIS.THIS WILL RESULT IN A PERIOD OF HEAVY SNOW AROUND THE MORNINGCOMMUTE. SNOW EXPECTED TO DEVELOP BY MIDNIGHT IN THE CT VALLEYTHEN QUICKLY SPREAD EWD ACROSS REST OF SNE.WE ISSUED WINTER WX ADVSY FOR ALL BUT S NH FOR GENERAL ACCUM 3-6".HEAVIEST QPF EXPECTED SE NEW ENG BUT HIGHER SNOW TO LIQUID RATIOSIN THE DISTANT INTERIOR WILL MAKE UP FOR LESS QPF. HOWEVER...THISSTORM STILL HAS THE POTENTIAL FOR HIGHER SNOW AMOUNTS AND EVENTUALUPGRADE TO A WARNING FOR THE I95 CORRIDOR TO CAPE COD GIVEN 06ZNAM TREND AND ALSO 03Z SREF WHICH ALSO INCREASED QPF AND SHOWEDDRAMATIC INCREASE IN PROBS FOR 4" NEAR THE S COAST AND EVEN A LOWPROB FOR 8". A FURTHER NW TRACK WOULD ALSO INTRODUCE PTYPE ISSUESOVER ACK AND OUTER CAPE WITH A BRIEF MIX OR CHANGE TO RAIN FRIMORNING.GIVEN THAT THE TREND BEFORE THIS WAS FOR DECREASING QPF ANDFURTHER OFFSHORE TRACK WE WERE NOT CONFIDENT ENOUGH TO GO WITH AWARNING. WE WILL LET NEXT SHIFT VIEW 12Z GUIDANCE TO DETERMINE IF THIS TREND IS FOR REAL.
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Exactly our point...BOS and Tolland (so as not to include eastern MA only) FTW....you FTL...:weight_lift:

If you can get your weenie goggles off long enough to look at H5 map depiction's you will be able to see that most all these storms have trended NW in the last 36 hrs on most of the models and this one looks like it will be no different..

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It was good to get a little more southern stream involved too, that probably enhances all those processes. A little more initial moisture to work with as well instead of trying to start from scratch with only Atlantic moisture trying to revive a fairly dry system....its already got some juice to it coming out of the OH Valley. Probably helps pump up ridge in front of it...sort of a lot of positive feedback processes in this particular setup.

Yeah that was big key. Those were the other small things I was looking at that I guess could have facilitated the trend.

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All the changes thus far have been a product of the northern stream digging more, which allows the surface low to start deepening further southwest and is thus stronger at our latitude. Problem is, without a clean phase, we get diffuse differential vorticity advection, uniformly lowering pressures across a wide area, and the surface low is therefore not getting any more intense with each model run (i.e. the low level vorticity is remaining about the same). In addition, this is why we aren't getting a low closing off at 700mb -- heights are being more dependent on temperature advection rather than DVA.

So really a simply NW trend (and nothing else) continuing today wouldn't yield much more QPF than is advertised currently, and would just result in some mixing issues.

Obviously excellent movements thus far in the model runs, that were to some extent anticipated (kudos Will and Kev).. Just saying what we might like to see to make things even more interesting.

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All the changes thus far have been a product of the northern stream digging more, which allows the surface low to start deepening further southwest and is thus stronger at our latitude. Problem is, without a clean phase, we get diffuse differential vorticity advection, uniformly lowering pressures across a wide area, and the surface low is therefore not getting any more intense with each model run (i.e. the low level vorticity is remaining about the same). In addition, this is why we aren't getting a low closing off at 700mb -- heights are more dependent on temperatures advection rather than DVA.

So really a simply NW trend (and nothing else) continuing today wouldn't yield much more QPF than is advertised currently, and would just result in some mixing issues.

Obviously excellent movements thus far in the model runs, that were to some extent anticipated (kudos Will and Kev).. Just saying what we might like to see to make things even more interesting.

Getting a little more southern stream involved (partially as a product of northern stream digging) is key for concentrating the vortmax is a little better. Those two pieces of energy seem to be feeding off eachother...as northern stream digs more, southern stream wants to get more involved....as southern stream wants to get more involved, it forces northern stream to dig a little more and consolidate the vortmax further south near the OH river valley.

You can see it happening well on the 12z NAM if you look at the 12h chart and then the 18h chart...the vortmax have combined forces.

nam500012l.gif

nam500018l.gif

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All the changes thus far have been a product of the northern stream digging more, which allows the surface low to start deepening further southwest and is thus stronger at our latitude. Problem is, without a clean phase, we get diffuse differential vorticity advection, uniformly lowering pressures across a wide area, and the surface low is therefore not getting any more intense with each model run (i.e. the low level vorticity is remaining about the same). In addition, this is why we aren't getting a low closing off at 700mb -- heights are being more dependent on temperature advection rather than DVA.

So really a simply NW trend (and nothing else) continuing today wouldn't yield much more QPF than is advertised currently, and would just result in some mixing issues.

Obviously excellent movements thus far in the model runs, that were to some extent anticipated (kudos Will and Kev).. Just saying what we might like to see to make things even more interesting.

You are right, We need this to close off and wrap up sooner rather then later, Low track is pretty optimum right now if we can get it to cooperate in the upper levels...

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