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12/1/10 convective threat

weatherwiz

By weatherwiz,
in New England

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Tropopause_Fold

Tropopause_Fold

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WOW...Wednesday looks like it could be pretty sick, NAM bufkit at BDL has 50-70 knots well below 5,000ft as does the GFS...both models also don't really show much if an inversion at all so when that intense of area with embedded convection occur it could get quite windy.

there isn't much of an inversion really but the profile is essentially isothermal so we'll really need some strong convective elements to produce much wind. like most of the S wind situations, we'll have to keep an eye for an embedded fine line of downpours or just some pockets of very heavy rain to produce much more than 35 knot gusts. somebody higher up might make out better....like the greens or berks...maybe ORH hills or someplace like MQE.

it'll be ripping good, no doubt, but i wouldn't count on anything tooo crazy.

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weatherwiz

weatherwiz

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there isn't much of an inversion really but the profile is essentially isothermal so we'll really need some strong convective elements to produce much wind. like most of the S wind situations, we'll have to keep an eye for an embedded fine line of downpours or just some pockets of very heavy rain to produce much more than 35 knot gusts. somebody higher up might make out better....like the greens or berks...maybe ORH hills or someplace like MQE.

it'll be ripping good, no doubt, but i wouldn't count on anything tooo crazy.

The one thing to watch for will be if a fine line can develop just out ahead of the cold front...the forcing/dynamics are there for it to happen but will once develop? The mid level lapse rates also don't appear to be that great but they do try to steepen some as the trough/front move closer and some colder air in the mid levels tries to work in. With the lapse rates being on the weaker side though elevated instability may not be all that great...I believe on the 17th (or whatever the date was) the ML lapse rates were on the steeper side so there was a bit more in the way of elevated instability and this really helped out areas to our south and west where they had a few tornadoes and some impressive convective winds.

The higher elevation areas may work out better...the strongest winds aloft aren't really all that high up and winds are pretty strong, even just above the sfc so anyone with elevation will have a much better chance.

We'll just have to see how high we can get those sfc temps to go...sometimes in these setups models tend to underdo them but we'll see.

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weatherwiz

weatherwiz

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Check out the swath of moisture transport. (For sake of brevity and save bandwidth radar omitted) IMPRESSIVE!

I think it's going to rain :arrowhead:

PWAT's are through the roof...like 1.5'' to 2''. Not sure where to find the anomaly maps and standard deviation maps for this type of stuff but I'd bet they would be pretty impressive.

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weatherwiz

weatherwiz

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Looks like b/c of the progressive nature of the system the best threat for any convection will remain off to our SW and then scout to our south across the Atlantic ocean...maybe...possibly some convection will hit eastern sections. Looks like though we don't truly get into the warm sector and this will tend to limit elevated instability.

This doesn't mean though we can't see any strong winds. While I'm not a huge fan of reflected radar simulations I think they are hitting this potential really good. They are showing a HUGE area of very heavy rainfall...given the anomalously high PWATS (as much as 3-4 SD above normal) and strong LLJ (as much as 3-5 SD above normal) there will be an incredible amount of moisture being drawn into the system and with such strong lift this should lead to some very heavy rainfall.

There certainly could be some pockets of wind gusts in the 55-65 mph in the HEAVIEST of the precip bands but this may not be a widespread occurrence, higher elevation areas would also stand a much better chance.

Flash flooding could certainly be a threat, even though the system is rather progressive, given the potential rainfall rates we could see as much as 1-3'' of rain in just a short amount of time, possibly in as little as 4-6 hours...this would certainly lead to at least poor drainage flooding and potentially some flash flooding in low-lying areas.

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moneypitmike

moneypitmike

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Posted this in the threat thread:

snapback.pngmoneypitmike, on 30 November 2010 - 05:25 AM, said:

Not to forget the "non-chrystaline" event on our doorstep, here's an interesting statement:

1.25 TO 1.5 INCH PW VALUES ACROSS WESTERN NEW ENGLAND INTO EASTERN NY STATE BY 18Z WEDNESDAY.

LOOKING AT THE NWS RAPID CITY PW CLIMATOLOGY STUDY AT KALB...NOTING

THESE VALUES ARE OVER THE 99TH PERCENTILE FOR EARLY DECEMBER.

I guess that would fit the definition of anamalous.

31.4/27. Temp rising since the 28.1 low at 1:30a.m.

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weatherwiz

weatherwiz

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If we are able to manage steeper low-level lapse rates, which we'd have to see higher sfc temps that would really help to increase the wind threat. At least there is a decent pressure gradient though and winds aloft are quite strong, even down to just above the sfc so pockets of intense rainfall could certainly help to draw some winds down.

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Wx4cast

Wx4cast

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Posted this in the threat thread:

snapback.pngmoneypitmike, on 30 November 2010 - 05:25 AM, said:

Not to forget the "non-chrystaline" event on our doorstep, here's an interesting statement:

1.25 TO 1.5 INCH PW VALUES ACROSS WESTERN NEW ENGLAND INTO EASTERN NY STATE BY 18Z WEDNESDAY.

LOOKING AT THE NWS RAPID CITY PW CLIMATOLOGY STUDY AT KALB...NOTING

THESE VALUES ARE OVER THE 99TH PERCENTILE FOR EARLY DECEMBER.

I guess that would fit the definition of anamalous.

31.4/27. Temp rising since the 28.1 low at 1:30a.m.

3-4 iso 5" Berks and Greens /Catskills and 'Dacks NY, those pwats are close to +4 SD

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weatherwiz

weatherwiz

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I don't think the winds will be overly impressive. Maybe some 45mph gusts but no big deal.

I really wish we were able to get some steeper low-level lapse rates in here, that would certainly be a big help. Winds should be fairly gusty at times tomorrow although the most intense of the winds may stay off to our SW, like across the NJ area. We'll have to see what we can get to develop tomorrow, if we can manage to develop a fine line of convection that could certainly help and could make for some gusts close to 50-55 mph although this probably won't be a widespread thing.

If anything I think the rainfall threat is more impressive and we could potential see 1-3''...perhaps 2-4'' in many locations in such a sort amount of time so some localized flash flooding is certainly possible.

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Tropopause_Fold

Tropopause_Fold

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I don't think the winds will be overly impressive. Maybe some 45mph gusts but no big deal.

yeah that seems to be the best bet...45 might even be generous for a lot of locations. there will probably be an isolated gust or two stronger than that - there always seems to be one or two locales that manage a 50 mph gust or something in one of these situations - but as we see time and again pre-frontal S wind events tend to be NBD.

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Wx4cast

Wx4cast

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yeah that seems to be the best bet...45 might even be generous for a lot of locations. there will probably be an isolated gust or two stronger than that - there always seems to be one or two locales that manage a 50 mph gust or something in one of these situations - but as we see time and again pre-frontal S wind events tend to be NBD.

I'd watch in N-S valleys for possible spinups and also if the NCFRB splits I would be concerned about areas below in "the splits" seeing some downburst/microburst potential. But yes probably nothing too widespread for the low spots better potential for the higher terrain.

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weatherwiz

weatherwiz

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I'd watch in N-S valleys for possible spinups and also if the NCFRB splits I would be concerned about areas below in "the splits" seeing some downburst/microburst potential. But yes probably nothing too widespread for the low spots better potential for the higher terrain.

This is exactly what occurred a few weeks ago in eastern NY...Columbia county I believe/ The NCFRB split into two and right at the edge of where the line split you got some incredible rotation. Here is a radar shot... (Well I'm at the library so I can't get the images to post but just go here...

http://www.americanwx.com/bb/index.php?/topic/971-pretty-neat-to-see/

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weatherwiz

weatherwiz

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The low-level lapse rates try to steepen as the afternoon goes on but they still appear to be a bit pultry. NAM continues to insist though on an incredibly intense band of precip moving through sometime in the late afternoon hours...PWATS of 2'' work into CT...totally insane. LLJ of 60-70 knots overspreads the region as well. NAM also has as much as 23-30 knots of wind just off the coast of CT tomorrow afternoon. I think southern CT could see gusts over 40 mph tomorrow...perhaps close to 50 mph in some spots, then the same occurring across parts of RI and SE MA as well...these areas could get close to 60F tomorrow, if not maybe a few ticks higher and this will help to steepen the LL lapse rates some.

Don't think this will be a widespread wind event but there should be pockets of wind damage tomorrow.

The potential for pockets of flash flooding may actually be a bit of a bigger threat consdiering the amount of rain that will be falling in such short amount of time and with some drains probably clogged with leaves.

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weatherwiz

weatherwiz

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This is just sick...the 12z GFS has pockets of 80-100 knots at 850mb...I don't know if I've ever seen winds THAT strong at that level this close to an event...also consistent with the NAM in the 60-70 kt LLJ at 925mb over the region. The GFS also looks to have 30-40 kt sfc winds over Long Island sound and southern CT tomorrow afternoon and then out over SE MA late in the afternoon...this is looking at the MSLP/sfc wind map on UCAR.

GFS looks pretty awful with ML lapse rates though so we'll definitely need some intense rainfall to help with winds.

Have to look closer when I get home, 2 minutes left here at the library.

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