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August 2012 Severe Thunderstorm/Convection Discussion


earthlight

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Guest Pamela

12z NMM amazingly wet with 7 inches + of rain forecast for SW CT, southern Westchester, and northern Long Island...

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12z NMM amazingly wet with 7 inches + of rain forecast for SW CT, southern Westchester, and northern Long Island...

seems like several of the hi-res models have been taking turns highlighting this area...taking a cluster with the pre-frontal trough and pulsing it up over this area, I think last nights hi-res NAM showed something similar.

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Guest Pamela

seems like several of the hi-res models have been taking turns highlighting this area...taking a cluster with the pre-frontal trough and pulsing it up over this area, I think last nights hi-res NAM showed something similar.

IIRC both models did a nice job with last weekends rains...

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post-187-0-60142100-1344193281_thumb.gif

MESOSCALE DISCUSSION 1708

NWS STORM PREDICTION CENTER NORMAN OK

0149 PM CDT SUN AUG 05 2012

AREAS AFFECTED...PORTIONS OF SRN NY...CENTRAL/ERN PA...NJ...MD...ERN

WV...NRN VA AND NRN DE

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 051849Z - 052015Z

CORRECTED FOR GEOGRAPHIC REFERENCES

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTMS DEVELOPING IN CLUSTERS/LINE SEGMENTS WILL LIKELY

CONTINUE TO INTENSIFY THROUGH REMAINDER OF AFTN WITH A SVR WIND AND

ISOLATED HAIL THREAT. AREA IS BEING MONITORED FOR A POSSIBLE WW.

DISCUSSION...TSTMS CONTINUE TO DEVELOP ACROSS CENTRAL/ERN PA SWD

INTO WRN VA IN DIFFERENTIAL HEATING ZONE AND AIDED BY OROGRAPHIC

FORCING. OBJECTIVE ANALYSIS INDICATED MLCAPE VALUES OF 1500 TO

LOCALLY 2500 J/KG. AREA IS ON THE SRN FRINGE OF STRONGER MID-LEVEL

FLOW ASSOCIATED WITH UPPER TROUGH ROTATING THROUGH ERN GREAT

LAKES/WRN NEW ENGLAND...HOWEVER SHEAR SHOULD BE SUFFICIENT FOR

MULTICELL STORMS/CLUSTERS CAPABLE OF PRODUCING DAMAGING WINDS. POOR

LAPSE RATES SHOULD LIMIT LARGE HAIL THREAT...BUT AN ISOLATED LARGE

HAIL REPORT IS POSSIBLE. CONVECTIVE TRENDS WILL CONTINUE TO BE

MONITORED AND A WW IS POSSIBLE IN THE NEXT FEW HOURS.

..BUNTING/THOMPSON.. 08/05/2012

ATTN...WFO...OKX...ALY...PHI...BGM...AKQ...CTP...LWX...

LAT...LON 40767804 42127746 42507629 42607508 41987366 40627381

39407499 38727607 38217698 38017780 38267841 38687886

40767804

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i disagree with okx not including at least essex/union in the watch. that line looks solid and instability/moisture isn't going anywhere

The storms are riding the periphery of decent 0-6km shear with values over 30 kts just back to the west over PA. But currently over our area, per the mesoanalysis, values are very unimpressive. In addition the guidance has some CIN building in by 22-00z. But EWR continues with a SW wind. I think it could've gone either way. But they're probably betting on the instability axis weakening by the time the storms get here. With meager ML Lapse rates it could be the right call by sunset. We'll see.

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The storms are riding the periphery of decent 0-6km shear with values over 30 kts just back to the west over PA. But currently over our area, per the mesoanalysis, values are very unimpressive. In addition the guidance has some CIN building in by 22-00z. But EWR continues with a SW wind. I think it could've gone either way. But they're probably betting on the instability axis weakening by the time the storms get here. With meager ML Lapse rates it could be the right call by sunset. We'll see.

unfortunately NAM bufkit is almost useless right now due to the model having too much early convection stabilizing us, but it hints at instability lasting til about midnight

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unfortunately NAM bufkit is almost useless right now due to the model having too much early convection stabilizing us, but it hints at instability lasting til about midnight

Yeah it had like .25" for a big area of NJ prior to 21z..didn't work out and it messes with the entire profile and environment afterwards.

The SPC WRF is encouraging...and the SBCAPE forecast for +2hrs on the RAP has 3500 joules over much of Northern NJ. So long as the better shear keeps sliding east with the convection, we should be ok.

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Yeah it had like .25" for a big area of NJ prior to 21z..didn't work out and it messes with the entire profile and environment afterwards.

The SPC WRF is encouraging...and the SBCAPE forecast for +2hrs on the RAP has 3500 joules over much of Northern NJ. So long as the better shear keeps sliding east with the convection, we should be ok.

True...but this cape stays over NJ, doesnt move east and dissipates around 7 pm, with CIN increasing afterwards...the cape really drops off big time by 8-9 esp city on east...looks like the line will die out in eastern nj, so i think the SPC has nailed this...but who knows.

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Cloud tops warming substantially as the convection is moving eastward, so weakening will ensue. We'll need to watch redevelopment ahead of the line if there is any severe to be sustained in the next couple of hours.

Why is this?

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Cloud tops warming substantially as the convection is moving eastward, so weakening will ensue. We'll need to watch redevelopment ahead of the line if there is any severe to be sustained in the next couple of hours.

Perhaps the southern portion, but I'm not seeing it in the northern.

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