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Slight Risk of Severe Storms 8/19


IsentropicLift

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Shear is weak. So t-storms will probably be slow-moving and very hit and miss. But with steep mid-level lapse rates, some CAPE, we see large hail and damaging wind gusts. Flash flooding will be big issue as well.

This is similar to yesterday, but honestly a little better. The cold pool aloft is even more impressive, a clear trigger in western PA where storms are already getting warned..

For whatever reason, our best severe weather days this season have been low shear days too it seems. Perhaps a seasonal trend, but coupled with the cold pool/mid-level lapse rates we've seen some tremendous storm stuctures in this area (even if they are of the pulse variety).

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Yesterday definitely overperformed especially after what the radar looked like around 3 or 4:00 compared to 4 hours later.

This is similar to yesterday, but honestly a little better. The cold pool aloft is even more impressive, a clear trigger in western PA where storms are already getting warned..

For whatever reason, our best severe weather days this season have been low shear days too it seems. Perhaps a seasonal trend, but coupled with the cold pool/mid-level lapse rates we've seen some tremendous storm stuctures in this area (even if they are of the pulse variety).

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Right and almost every county in NJ/NYC metro was under a warning at one point. We've had days where we were in tornado or Severe tstorm watches and ended up with practically nothing

Yeah I have to agree, we weren't even slight risked yesterday and I saw quarter sized hail. It seems the days that should be more likely to see severe weather we don't get much of anything.

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Yeah I'm not going to be fooled again just because of low shear. Like a seasonal trend in the winter, sometimes you just gotta go with it. Today is looking really good in my opinion if past severe days this season have meant anything.

Your right I gotta say this summer has been quite the opposite of what you'd be expecting. We get the severe storms on days that really weren't all that favorable for them and when we get tornado/severe storm watches its practically been a bust quite a few times this year. Today is looking good today as far as severe potential again though

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This is similar to yesterday, but honestly a little better. The cold pool aloft is even more impressive, a clear trigger in western PA where storms are already getting warned..

For whatever reason, our best severe weather days this season have been low shear days too it seems. Perhaps a seasonal trend, but coupled with the cold pool/mid-level lapse rates we've seen some tremendous storm stuctures in this area (even if they are of the pulse variety).

I agree. I don't think we'll see any organized squall line or tornadoes. But any t-storm would have potential to go severe quick and reach high severe levels.

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mcd2017.gif

MESOSCALE DISCUSSION 2017

NWS STORM PREDICTION CENTER NORMAN OK

1143 AM CDT FRI AUG 19 2011

AREAS AFFECTED...PARTS OF CNTRL/ERN PA...SRN NY...NJ

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 191643Z - 191745Z

TRENDS ARE BEING MONITORED FOR THE POSSIBILITY OF A SEVERE THREAT

THAT COULD REQUIRE A WATCH.

SCATTERED STORM DEVELOPMENT IS NOW WELL UNDERWAY ACROSS MUCH OF THE

NORTHEAST...BENEATH GENERALLY LIGHT...BROADLY CYCLONIC MID/UPPER

FLOW. A MID-LEVEL COLD POCKET WITHIN THIS REGIME APPEARS TO PROVIDE

THE FOCUS FOR ONE CLUSTERING OF STORMS NOW SPREADING INTO/THROUGH

THE NORTHERN ALLEGHENY MOUNTAINS AREA OF PENNSYLVANIA. EAST OF THIS

ACTIVITY...AND IN FACT THROUGH MUCH OF THE NORTHEAST...A MOIST

BOUNDARY LAYER CONTINUES TO GRADUALLY DESTABILIZE...WITH LOW-LEVEL

LAPSE RATES STEEPENING IN RESPONSE TO INSOLATION...AND MIXED LAYER

CAPE BECOMING MODERATELY LARGE. THIS SHOULD CONTINUE TO SUPPORT

INCREASING/INTENSIFYING THUNDERSTORM ACTIVITY THROUGH THE AFTERNOON

HOURS. THERMODYNAMIC PROFILES MAY BE SUFFICIENT FOR SOME HAIL AND

LOCALIZED DOWNBURSTS IN STRONGER STORMS...BUT VERY WEAK DEEP LAYER

MEAN FLOW AND SHEAR WILL PROBABLY MINIMIZE THE RISK FOR ORGANIZED

SEVERE STORMS. IT MAY BE POSSIBLE THAT CONSOLIDATING COLD POOLS

COULD SUPPORT UPSCALE CONVECTIVE GROWTH ACROSS THE REMAINDER OF

CENTRAL AND EASTERN PENNSYLVANIA INTO NEW JERSEY AND PORTIONS OF THE

LOWER HUDSON VALLEY BY THE 21-22Z TIME FRAME. IF THIS OCCURS

...THERE MAY BE SOME POTENTIAL FOR BROADER SCALE STRONG WINDS ALONG

A DEVELOPING GUST FRONT. BUT PEAK WINDS MAY GENERALLY REMAIN BELOW

SEVERE CRITERIA...EXCEPT PERHAPS WHERE LOCALLY ACCELERATED BY

TERRAIN FEATURES.

..KERR.. 08/19/2011

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SEL1

URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 791

NWS STORM PREDICTION CENTER NORMAN OK

105 PM EDT FRI AUG 19 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

EXTREME WESTERN CONNECTICUT

EXTREME NORTHERN DELAWARE

EXTREME WESTERN MASSACHUSETTS

NEW JERSEY

SOUTHEAST NEW YORK

EASTERN PENNSYLVANIA

COASTAL WATERS

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 105 PM UNTIL 900

PM EDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 90

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES WEST

NORTHWEST OF PITTSFIELD MASSACHUSETTS TO 35 MILES SOUTH SOUTHEAST

OF HARRISBURG PENNSYLVANIA. FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.

DISCUSSION...SCATTERED PULSE-TYPE STORMS WILL CONTINUE TO INCREASE

IN COVERAGE/INTENSITY DURING THE NEXT FEW HOURS IN CONJUNCTION WITH

DAYTIME HEATING/DESTABILIZATION...AS WELL AS STORM/OUTFLOW MERGERS.

THOUGH DEEP-LAYER VERTICAL SHEAR WILL REMAIN WEAK ACROSS THE WATCH

AREA...MLCAPE OF 1500-2000 J/KG AND RELATIVELY COOL MIDLEVEL

TEMPERATURES WILL SUPPORT MARGINALLY SEVERE HAIL WITH THE STRONGER

UPDRAFTS. AS THE STORMS COLLAPSE...ISOLATED DAMAGING DOWNBURSTS

WILL ALSO BE POSSIBLE.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM

MOTION VECTOR 27015.

...THOMPSON

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WWUS40 KWNS 191704WWP1

SEVERE THUNDERSTORM WATCH

PROBABILITIES FOR WS 0791

NWS STORM PREDICTION CENTER

NORMAN OK

1204 PM CDT FRI

AUG 19 2011WS 0791

PROBABILITY TABLE:

PROB OF 2 OR MORE TORNADOES : <05%

PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : <02%

PROB OF 10 OR MORE SEVERE WIND EVENTS : 50%

PROB OF 1 OR MORE WIND EVENTS >= 65 KNOTS : 10%

PROB OF 10 OR MORE SEVERE HAIL EVENTS : 50%

PROB OF 1 OR MORE HAIL EVENTS >= 2 INCHES : 10%

PROB OF 6 OR MORE COMBINED SEVERE HAIL/WIND EVENTS : 90%

&&ATTRIBUTE TABLE:

MAX HAIL /INCHES/ : 1.5

MAX WIND GUSTS SURFACE /KNOTS/ : 60

MAX TOPS /X 100 FEET/ : 450

MEAN STORM MOTION VECTOR /DEGREES AND KNOTS/ : 27015

PARTICULARLY DANGEROUS SITUATION : NO

&&FOR A COMPLETE GEOGRAPHICAL DEPICTION OF THE WATCH ANDWATCH EXPIRATION INFORMATION SEE WOUS64 FOR WOU1.$

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If you take a look at the storm evolutions in PA right now its very similar to what happened last night. Big slow movers and when one storm pulses down another one takes over out ahead of the last one. They go briefly severe and if your lucky enough to be under one on the way up, you have a decent shot at seeing some hail today I think.

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