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Severe weather thread number ...I think X ?


Typhoon Tip

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MESOSCALE DISCUSSION 1608

NWS STORM PREDICTION CENTER NORMAN OK

0237 PM CDT THU JUL 26 2012

AREAS AFFECTED...PORTIONS OH...NERN KY...WV...PA...SERN NY...SRN NEW

ENGLAND...NJ.

CONCERNING...SEVERE THUNDERSTORM WATCH 524...

VALID 261937Z - 262130Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 524

CONTINUES.

SUMMARY...CONTINUE WW ALONG/AHEAD OF STG-SVR TSTMS NOW OVER NRN/WRN

PORTIONS. NEW WW WILL BE ISSUED SOON...DOWNSHEAR FOR ERN PA EWD

TOWARD SWRN NEW ENGLAND AND LONG ISLAND INCLUDING NYC METRO AREA.

DISCUSSION...INCREASINGLY WELL-ORGANIZED SQUALL LINE...WITH EMBEDDED

BOW/LEWP SEGMENTS...WAS EVIDENT AT 1930Z FROM STEUBEN COUNTY NY SWWD

TO COLUMBIANA COUNTY OH...BECOMING MORE BKN SWWD OVER SERN OH. THIS

ACTIVITY CONTINUES MOVING EWD 40-50 KT...WITH LOCAL VARIATIONS AS

COLD-POOL SURGES OCCUR...AND WILL MOVE INTO FAVORABLY

UNSTABLE/BUOYANT AIR MASS ACROSS CENTRAL/ERN PA AND EVENTUALLY EWD

TO SRN NEW ENGLAND. MIDLEVEL LAPSE RATES WILL CONTINUE TO DIMINISH

WHILE CINH INCREASES WITH EWD EXTENT...PER 18Z RAOBS.

HOWEVER...STG BOUNDARY-LAYER HEATING IS FCST...WITH LOW-LEVEL WLYS

ALSO CONTRIBUTING TO CAPE THROUGH MOISTURE ADVECTION/TRANSPORT. AS

SUCH...FAVORABLE AIR MASS WILL SPREAD/DEVELOP EWD OVER CT/RI/LONG

ISLAND. THIS CORRIDOR WILL REMAIN BENEATH SRN RIM OF STRONGEST

MIDLEVEL WINDS...CONTRIBUTING TO EFFECTIVE SHEAR MAGNITUDES 40-50

KT. DIFFUSE SFC WARM FRONT WILL CONTINUE TO MOVE NEWD OVER ERN/NRN

PA INTO SERN NY. NEARLY UNIDIRECTIONAL WIND PROFILES SHOULD

CONTINUE...BUT WITH SLGT VEERING IN LOWEST 1-2 KM AGL INVOF WARM

FRONT.

..EDWARDS.. 07/26/2012

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The better dewpoints are starting to make more progress into CT/RI now...which is good for trying to maintain the storms because the ML lapse rates are pretty lousy and we can't really count on those for help.

We'll have to see how far north they get as the evening wears on.

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What do you guys make of the apparent boundary along the Hudson? Not oriented right for WF, which we've identified as elsewhere anyway, so what is it? Seems like more than just the usual river valley effect, is this an OFB? Shows up best here:

vtm_sf.gif?1343332301023

Note: time sensitive image, because I haven't completely figured out how to upload and display stuff yet...

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Likelihood of 65 kt+ Wind: "High"

WWUS40 KWNS 262000

WWP7

SEVERE THUNDERSTORM WATCH PROBABILITIES FOR WS 0527

NWS STORM PREDICTION CENTER NORMAN OK

0300 PM CDT THU JUL 26 2012

WS 0527

PROBABILITY TABLE:

PROB OF 2 OR MORE TORNADOES : 20%

PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 10%

PROB OF 10 OR MORE SEVERE WIND EVENTS : >95%

PROB OF 1 OR MORE WIND EVENTS >= 65 KNOTS : 70%

PROB OF 10 OR MORE SEVERE HAIL EVENTS : 40%

PROB OF 1 OR MORE HAIL EVENTS >= 2 INCHES : 20%

PROB OF 6 OR MORE COMBINED SEVERE HAIL/WIND EVENTS : >95%

&&

ATTRIBUTE TABLE:

MAX HAIL /INCHES/ : 2.0

MAX WIND GUSTS SURFACE /KNOTS/ : 70

MAX TOPS /X 100 FEET/ : 500

MEAN STORM MOTION VECTOR /DEGREES AND KNOTS/ : 27045

PARTICULARLY DANGEROUS SITUATION : NO

&&

FOR A COMPLETE GEOGRAPHICAL DEPICTION OF THE WATCH AND

WATCH EXPIRATION INFORMATION SEE WOUS64 FOR WOU7.

$$

As an aside, 90%+ chances haven't always worked out for us in the past...

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The better dewpoints are starting to make more progress into CT/RI now...which is good for trying to maintain the storms because the ML lapse rates are pretty lousy and we can't really count on those for help.

We'll have to see how far north they get as the evening wears on.

90/74 on south shore of long island

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SWCT NYC NJ under the gun from this line it seems

Sure does.

I expect the line to expand north. The atmosphere is going to rapidly destabilize for sfc based parcels as for north as Albany with warm front racing north.

Awesome.

There goes the Severe Thunderstorm Watch for much of Western MA and CT

I typicallly cringe when I'm on the edge of a watch zone. But, when the adjacent ones 8 miles and 12 miles away have a tornado watch, I take comfort. :)

Good luck everyone!

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Hmmm...

OH TO SRN NEW ENGLAND

ADJUSTED MODERATE RISK TO ALONG AND AHEAD OF INITIAL QLCS IN SWRN NY

TO ERN OH AND UPSTREAM DEVELOPMENT OCCURRING BACK IN WRN OH.

ALTHOUGH SEVERE WIND GUSTS HAVE YET TO BE MEASURED BY ANY ASOS/AWOS

OBSERVATIONS...50-55 KT EWD MOVEMENT HAS BEEN NOTED WITH THIS

INITIAL LINE AND 18Z PIT/OKX RAOBS ARE CERTAINLY SUPPORTIVE OF FAST

ELY PROPAGATION. CONSIDERED UPGRADE TO HIGH RISK BUT RELATIVELY

MODEST MID/HIGH-LEVEL LAPSE RATES SAMPLED IN REGIONAL 18Z RAOBS

SUGGEST MODERATE RISK APPEARS MOST APPROPRIATE ATTM.

NEVERTHELESS...NUMEROUS TO WIDESPREAD COVERAGE OF DAMAGING WINDS IS

LIKELY AS THE NUMBER OF BOWING SEGMENTS INCREASE WITH AN ASSOCIATED

THREAT OF ISOLATED INTENSE WIND DAMAGE AND BRIEF TORNADOES.

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Hmmm...

OH TO SRN NEW ENGLAND

ADJUSTED MODERATE RISK TO ALONG AND AHEAD OF INITIAL QLCS IN SWRN NY

TO ERN OH AND UPSTREAM DEVELOPMENT OCCURRING BACK IN WRN OH.

ALTHOUGH SEVERE WIND GUSTS HAVE YET TO BE MEASURED BY ANY ASOS/AWOS

OBSERVATIONS...50-55 KT EWD MOVEMENT HAS BEEN NOTED WITH THIS

INITIAL LINE AND 18Z PIT/OKX RAOBS ARE CERTAINLY SUPPORTIVE OF FAST

ELY PROPAGATION. CONSIDERED UPGRADE TO HIGH RISK BUT RELATIVELY

MODEST MID/HIGH-LEVEL LAPSE RATES SAMPLED IN REGIONAL 18Z RAOBS

SUGGEST MODERATE RISK APPEARS MOST APPROPRIATE ATTM.

NEVERTHELESS...NUMEROUS TO WIDESPREAD COVERAGE OF DAMAGING WINDS IS

LIKELY AS THE NUMBER OF BOWING SEGMENTS INCREASE WITH AN ASSOCIATED

THREAT OF ISOLATED INTENSE WIND DAMAGE AND BRIEF TORNADOES.

50-55 knot eastward progression? Zoinks--any sense of reference for what is more typical?

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