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Central PA Thread - Summer 2012


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On a serious note, NWS isn't really talking in specifics about tomorrow. Guess I can't blame them though, it's tough forecasting severe weather.

Yea, they did update the near term recently to talk about the first chance of storms in the early dawn/daylight hours. Earlier today some models had suggested a severe line coming through western and central PA during that time, but the new NAM and HRRR runs has suggested that the convection stays mainly north but still suggests some scattered thunderstorms trying to form. This is with the initial surge of the warm front. Per mesoanalysis the major influx of CAPE and moisture is just starting to reach western PA. Pretty likely the next short term update will include some detail on trying to hash out the plethora of threats we have later tomorrow... most likely coming after SPC updates their D1 map soon, and I'm really curious to see it. I personally think it is a tough forecast just from the aspect of that pretty much all severe options are on the table tomorrow so to speak... from discrete supercells that could produce some very large hail and tornadoes, to clusters/bows, and of course the threat of an organized MCS/full blown derecho. Regardless of storm type, the enhanced high wind threat is pretty real.

I'm not sure what to think about any tornado threat quite yet. The NAM moves a core of decent EHI values (at least 2-3) from western PA thru northern PA as the afternoon wears on. Those are pretty high values, and coupled with the other parameters in place I would be wary of discrete cells, as they could drop a tornado. SPC might paint western/northern PA in as much as a 10% risk IMO, which is pretty decent for our area but technically a high end slight risk in regards to that particular threat. Otherwise, I expect SPC to maintain their overall moderate risk as well as their hatched area for enhanced threats, specifically for wind... but I don't think damaging hail should be forgotten about either and i just covered how I felt about the tornado threat. Don't think we'll see the rare high risk unless we get something organized rolling towards us tomorrow.

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Yea, they did update the near term recently to talk about the first chance of storms in the early dawn/daylight hours. Earlier today some models had suggested a severe line coming through western and central PA during that time, but the new NAM and HRRR runs has suggested that the convection stays mainly north but still suggests some scattered thunderstorms trying to form. This is with the initial surge of the warm front. Per mesoanalysis the major influx of CAPE and moisture is just starting to reach western PA. Pretty likely the next short term update will include some detail on trying to hash out the plethora of threats we have later tomorrow... most likely coming after SPC updates their D1 map soon, and I'm really curious to see it. I personally think it is a tough forecast just from the aspect of that pretty much all severe options are on the table tomorrow so to speak... from discrete supercells that could produce some very large hail and tornadoes, to clusters/bows, and of course the threat of an organized MCS/full blown derecho. Regardless of storm type, the enhanced high wind threat is pretty real.

I'm not sure what to think about any tornado threat quite yet. The NAM moves a core of decent EHI values (at least 2-3) from western PA thru northern PA as the afternoon wears on. Those are pretty high values, and coupled with the other parameters in place I would be wary of discrete cells, as they could drop a tornado. SPC might paint western/northern PA in as much as a 10% risk IMO, which is pretty decent for our area but technically a high end slight risk in regards to that particular threat. Otherwise, I expect SPC to maintain their overall moderate risk as well as their hatched area for enhanced threats, specifically for wind... but I don't think damaging hail should be forgotten about either and i just covered how I felt about the tornado threat. Don't think we'll see the rare high risk unless we get something organized rolling towards us tomorrow.

I think 10% tornado, 30% hatched hail and 45% hatched winds in 130 update. As max values.

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mcd1597.gif

MESOSCALE DISCUSSION 1597

NWS STORM PREDICTION CENTER NORMAN OK

1215 AM CDT THU JUL 26 2012

AREAS AFFECTED...FAR NORTHERN OH/NORTHWEST PA/WESTERN NY

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 260515Z - 260715Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...AT LEAST ISOLATED DAMAGING WIND/SEVERE HAIL POTENTIAL IS

LIKELY TO DEVELOP INTO PORTIONS OF FAR NORTHERN OH AND /MORE SO/

NORTHWEST PA AND WESTERN NY OVERNIGHT. A SEVERE TSTM WATCH MAY BE

NEEDED.

DISCUSSION...A QUASI-LINEAR MCS CONTINUES TO DEVELOP/EXPAND AND

GRADUALLY ACCELERATE SOUTHEASTWARD ACROSS LOWER MI/SOUTHERN ONTARIO

AS OF 05Z. THIS ACTIVITY SEEMS LIKELY TO PERSIST EAST-SOUTHEASTWARD

OVERNIGHT WITHIN A BELT OF MODERATELY STRONG LOW-MID LEVEL

FLOW...POTENTIALLY INTO PARTS OF NORTHERN OH/NORTHWEST PA/WESTERN

NY...PERHAPS AS EARLY AS 07Z-08Z NEAR THE LOWER LAKES. PRECEDING THE

MCS...IT IS YET RELATIVELY DRY/STABLE AS PER THE 00Z OBSERVED

SOUNDING FROM BUFFALO/PITTSBURGH. HOWEVER...A WARM FRONT CONTINUES

TO STEADILY APPROACH THE REGION FROM THE WEST WITH AID OF A 30-40 KT

LOW LEVEL JET PER REGIONAL WSR-88D VWPS ACROSS INDIANA/OH/MI...WITH

THE CONTINUED EAST-NORTHEASTWARD ADVECTION OF A POTENTIALLY UNSTABLE

AIRMASS AS SAMPLED BY THE 00Z WILMINGTON OH OBSERVED RAOB /5000+ J

PER KG MLCAPE/. WITH GREATER ACCESS TO WARM/MOIST ADVECTION JUST

ABOVE THE SURFACE...AT LEAST THE WEST-SOUTHWESTERN FLANK OF THE

APPROACHING MCS MAY POSE A DAMAGING WIND/PERHAPS SEVERE HAIL RISK

OVERNIGHT INTO PORTIONS OF OH/PA/NY.

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Update generally was what I was expecting from categorical and specific threats. Whiffed a bit on my expectation with tornado threat, with a 2% in western/north central and a 5% in northeastern PA/NY southern tier. Ultimately any enhanced tornado threat will likely evolve where we can get some separate supercells cranked with a combo of the max helicity and daytime heating. But yea, any way you slice it, we're looking at a pretty busy day tomorrow.

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Looking at my model, pretty consistent with the strong potential for significant winds possible across the OH-PA-NY regions. Anywhere from 70-85mph convective gusts possible. I am tracking highest potential based on indices for any type of tornadoes around the Jamestown,NY area. Seeing values around 17-18Z of LI's around -7, SFC CAPE aroudn 2,700 J/KG, 0-3KM ML CAPE around 164 J/KG, and EHI's right around 2. Posted matrix on update.htm link

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BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE PITTSBURGH PA

247 AM EDT THU JUL 26 2012

THE NATIONAL WEATHER SERVICE IN PITTSBURGH HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

SOUTHEASTERN CARROLL COUNTY IN EAST CENTRAL OHIO...

HARRISON COUNTY IN EAST CENTRAL OHIO...

JEFFERSON COUNTY IN EAST CENTRAL OHIO...

NORTH CENTRAL OHIO COUNTY IN NORTHERN WEST VIRGINIA...

HANCOCK COUNTY IN NORTHERN WEST VIRGINIA...

BROOKE COUNTY IN NORTHERN WEST VIRGINIA...

* UNTIL 330 AM EDT

* AT 244 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED

A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING QUARTER TO

GOLF BALL SIZE HAIL. THESE STORMS WERE LOCATED ALONG A LINE

EXTENDING FROM KILGORE TO FREEPORT...MOVING EAST AT 25 MPH.

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Some of those cells up to like 60-65 DBZ nearing PITT. Lots of lightning. Warm front action.

Yea these storms were predicted pretty well by the HRRR and in most of the recent runs they were the main action that tried to cross central PA. Still see hints of the mcs dropping se in the latest run as well but largely dissipated as it drops into the area. We'll have to see what we have left once it crosses the lake.

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