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October 19 Severe Obs/Disc


Ellinwood

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So this happened:

day1probotlk_20111019_1200_torn_prt.gif

day1probotlk_20111019_1200_wind_prt.gif

...CAROLINAS/MID-ATLANTIC STATES/DELMARVA/PA...

THE BRUNT OF A BROAD/DEEP LONGWAVE TROUGH WILL GENERALLY SHIFT

EAST-NORTHEASTWARD FROM THE LOWER/MIDDLE MS RIVER VALLEY TOWARD THE

OH VALLEY/APPALACHIANS THROUGH TONIGHT. INITIALLY TODAY...SEVERE

POTENTIAL WILL BE FOCUSED ACROSS AREAS SUCH AS THE COASTAL

CAROLINAS...WHERE STRONG/MODESTLY VEERING LOW/MID TROPOSPHERIC FLOW

WILL COINCIDE WITH AN INLAND DEVELOPING MOIST/UNSTABLE NEAR-COASTAL

AIRMASS. IN THIS CASE...CONCERN EXISTS INTO THE MIDDAY HOURS FOR THE

POSSIBILITY OF SUPERCELLS CAPABLE OF A TORNADO OR TWO AS WELL AS

DAMAGING WINDS MAINLY FOR COASTAL AREAS.

INTO THE UPSTATE CAROLINAS/MID-ATLANTIC REGION AND A BIT LATER

TODAY...POTENTIAL FOR STRONG/SEVERE TSTMS IS EXPECTED TO INCREASE

THIS AFTERNOON/TONIGHT AS A MOIST INFLUX CONTINUES AND THE PARENT

CYCLONE UNDERGOES A DEEPENING PHASE/BECOMES NEGATIVELY TILTED. WHILE

A SHALLOW NEAR-SURFACE STABLE LAYER MAY TEND TO PERSIST ACROSS THE

REGION AND DESTABILIZATION SHOULD OTHERWISE REMAIN

MODEST...PRONOUNCED HEIGHT FALLS/DPVA AND DRAMATICALLY STRENGTHENING

DEEP LAYER SOUTH-SOUTHWESTERLY FLOW PROVIDES CONCERN FOR THE

DEVELOPMENT OF A LOW-TOPPED/FAST-MOVING CONVECTIVE LINE IN VICINITY

OF AN EAST-NORTHEASTWARD ACCELERATING COLD FRONT FROM MID/LATE

AFTERNOON THROUGH TONIGHT. EVEN WITH RELATIVELY MODEST

BUOYANCY...THE DEGREE OF FORCING/VERTICAL SHEAR MAY YIELD SOME

SUPERCELLS /ESPECIALLY EARLY IN THE CONVECTIVE CYCLE/ ASIDE FROM THE

EVOLUTION OF A FAST-MOVING CONVECTIVE LINE WITH EMBEDDED BOWS. IN

THIS SCENARIO...DAMAGING WINDS/POSSIBLE TORNADOES AND PERHAPS SOME

HAIL WILL BE POSSIBLE...WITH THE RELATIVELY GREATEST POTENTIAL

EXPECTED TO SPREAD/INCREASE FROM CENTRAL/NORTHERN NC INTO CENTRAL

VA/MD THIS AFTERNOON/EVENING. AT LEAST A MARGINAL/ISOLATED DAMAGING

WIND THREAT COULD VERY WELL CONTINUE WELL THROUGH THE NIGHT INTO

PORTIONS OF PA/DELMARVA AND EVEN SOUTHERN NY.

...OH VALLEY TO THE APPALACHIANS...

WITHIN THE UPPER JET EXIT REGION...LOW-TOPPED STORMS ARE EXPECTED TO

DEVELOP THIS AFTERNOON ACROSS THE REGION IN VICINITY OF THE SURFACE

COLD/OCCLUDED FRONT. WHILE BOUNDARY LAYER MOISTURE/INSTABILITY WILL

BE MODEST...STEEP LOW/MID LEVEL LAPSE RATES AND CONSIDERABLE

VERTICAL SHEAR MAY YIELD AN AFTERNOON/EARLY EVENING RISK FOR SEVERE

HAIL/WIND AND PERHAPS EVEN A BRIEF TORNADO. UNCERTAINTY REGARDING

THE DEGREE OF DESTABILIZATION PRECLUDES A FURTHER EXPANSION OF THE

CATEGORICAL SLIGHT RISK AT THIS TIME.

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Latest SREFs from the SPC put eastern VA and NE NC in the hot zone for TORs, so long as stuff can form with the drier air rushing into the mid/upper levels. NAM is decent, RUC is crap WRT instability.

GFS is similar to the NAM, with slightly more moisture in the mid/upper levels.

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Here is that line on the leading edge of the coldfront and upper level support. You can see the area of high RH in nrn VA. Maybe one of those fast moving lines with embedded stronger cells within it?

I've found those types of lines can sometimes perform well, if you have the instability. I guess time will tell on that. SPC WRF wasn't too enthused fwiw.

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I had a lot of questions regarding timing but I must say at this point in time its setting up rather nicely for some good storms. Clearing coming in from the south should bring no problems with innstability and there is an impressive amount of shear over the area with good height falls and rates. Don't see what will hold this one back.

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I had a lot of questions regarding timing but I must say at this point in time its setting up rather nicely for some good storms. Clearing coming in from the south should bring no problems with innstability and there is an impressive amount of shear over the area with good height falls and rates. Don't see what will hold this one back.

Mid-Atlantic fail bubble

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Well that was a surprising outlook to wake up to. Especially given the previous day 2 outlook from yesterday.......

The 500mb pattern was screaming this.

It'll probably not produce as well as the outlook makes it seem, but it shouldnt be that surprising.

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I had a lot of questions regarding timing but I must say at this point in time its setting up rather nicely for some good storms. Clearing coming in from the south should bring no problems with innstability and there is an impressive amount of shear over the area with good height falls and rates. Don't see what will hold this one back.

If something can go wrong, it will here.

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the only thing left in my morning is to troll DT about his coastal low

Was he claiming this would phase into a monster nor'easter??

There is a weak surface low embedded in an overall low ambient pressure pattern....but too bad we could get the upper level support closer to this low.

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Was he claiming this would phase into a monster nor'easter??

There is a weak surface low embedded in an overall low ambient pressure pattern....but too bad we could get the upper level support closer to this low.

Yeah.. he backed off a minor bit recently but was still calling for a nor'easter and making fun of those who didnt through the day before yesterday. Then yesterday he was talking about a 2nd major coastal low next week and telling his "fans" on FB that there was no storm risk today.

Sometimes it's shocking to me that a number of mets don't actually look at the pattern but just regurgitate model output. When there is a giant closed neg tilt progressive trough cutting to our west it's worth considering a tornado risk even if it does not happen based on our history of tornadoes down here.Not to mention the NW trend and La Nina (or sans La Nina)

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Yeah.. he backed off a minor bit recently but was still calling for a nor'easter and making fun of those who didnt through the day before yesterday. Then yesterday he was talking about a 2nd major coastal low next week and telling his "fans" on FB that there was no storm risk today.

Sometimes it's shocking to me that a number of mets don't actually look at the pattern but just regurgitate model output. When there is a giant closed neg tilt progressive trough cutting to our west it's worth considering a tornado risk even if it does not happen based on our history of tornadoes down here.Not to mention the NW trend and La Nina (or sans La Nina)

Given the shear at the surface, it's not ridiculous to think there could be cells rotating. When I first posted to you yesterday..I thought you guys would be wedged which you are...but we talked about that feature you described, maybe giving you guys a round late day/early evening. It still seems a little questionable to me, but good luck. Sometimes these things surprise. Hopefully you can get into a pseudo warm sector on se winds.

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Given the shear at the surface, it's not ridiculous to think there could be cells rotating. When I first posted to you yesterday..I thought you guys would be wedged which you are...but we talked about that feature you described, maybe giving you guys a round late day/early evening. It still seems a little questionable to me, but good luck. Sometimes these things surprise. Hopefully you can get into a pseudo warm sector on se winds.

We often don't do superb in high shear low cape setups. Certainly reason not to go all in etc. But I don't think most locals even mentioned the chance of storms today. As far back as late last week (timing was a day or so earlier) this looked like a potential outcome. Plus I think there is something to pattern memory.

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I see a bit of MUCAPE trying to move up into the region along with that batch of showers in the central Carolinas. Surface-based instability still offshore for now as the convection along the coast blocks the feed from getting into the region.

Nice to see some clearing this morning, though it looks rather cloudy to the south.

I'm starting to come around a little bit... feeling optimistic about the cold front stuff moving through central VA in the early-mid evening and through the DC region mid-late evening. Chasing would be hard as the timing would mean limited daylight, but we'll see how it looks in several hours when the decision to go has to be made.

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Latest SPC - Tornado threat pulled way back in terms of the 5% area. Wind still 30%.

Good thing I got my gloating in early.

Seriously their early outlook was surprisingly bullish on the 5%.

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