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More (Heavy?) Rain/T-Storms 8/18-8/21 Discussion/OBS


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Looks like my office and OKX basically requesting a watch box from SPC panned out fairly well this afternoon. Interestingly enough, the 12z SPC WRF actually had the convection exploding into a solid line across southeast PA then weaken as it moved into NJ. Based on radar loops posted earlier and latest radar trends, that is indeed what happened. Also on the radar loop posted earlier, impressive outflow boundary across Chester to Bucks counties then this collided with the ouflow moving northwestward from the storms in southern NJ. The added lift by these allowed new convection to develop and quickly form into a line before getting choked off. Interesting day!

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Looks like my office and OKX basically requesting a watch box from SPC panned out fairly well this afternoon. Interestingly enough, the 12z SPC WRF actually had the convection exploding into a solid line across southeast PA then weaken as it moved into NJ. Based on radar loops posted earlier and latest radar trends, that is indeed what happened. Also on the radar loop posted earlier, impressive outflow boundary across Chester to Bucks counties then this collided with the ouflow moving northwestward from the storms in southern NJ. The added lift by these allowed new convection to develop and quickly form into a line before getting choked off. Interesting day!

Good call, indeed.

Outflow boundaries were crazy colliding like they did.

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Localized, but very nasty storm in some areas. I was in Royersford, Trappe, Collegeville. Very heavy rain, high wind, many many close lightning strikes. Pretty strong in Collegeville and then did not do much in Worcester. Seems like it slid to the south. Flooding in Norristown, and then over into Plymouth, Whitemarsh and Upper Dublin area. Numerous fire calls. (wires, afa, flooded roads and at least one working fire in Upper Dublin.) One call - not sure what it really was once EMS arrived on the scene, but it was dispatched as an electrocution in the car on Rt 422.

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Storms in Mont Co. are sliding a mile or two south of me.....constant CG lightning to my south, bright skies to my north. Not even raining here (atleast not yet).

We got a 10 minute pounding in Royersford...f'n crazy lightning.

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Looks like my office and OKX basically requesting a watch box from SPC panned out fairly well this afternoon. Interestingly enough, the 12z SPC WRF actually had the convection exploding into a solid line across southeast PA then weaken as it moved into NJ. Based on radar loops posted earlier and latest radar trends, that is indeed what happened. Also on the radar loop posted earlier, impressive outflow boundary across Chester to Bucks counties then this collided with the ouflow moving northwestward from the storms in southern NJ. The added lift by these allowed new convection to develop and quickly form into a line before getting choked off. Interesting day!

Good call to go to bat requesting one...panned out pretty darn well.

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We got a 10 minute pounding in Royersford...f'n crazy lightning.

Looked like you were on the fence as well, but got hit a bit harder than me.

As Chief said in his post, those storms slid "just" south of Worcester/Skippack/Graterford. I could tell Trappe was getting nailed as pitch black skies and constant lightning could be seen to my south.

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Looks like my office and OKX basically requesting a watch box from SPC panned out fairly well this afternoon. Interestingly enough, the 12z SPC WRF actually had the convection exploding into a solid line across southeast PA then weaken as it moved into NJ. Based on radar loops posted earlier and latest radar trends, that is indeed what happened. Also on the radar loop posted earlier, impressive outflow boundary across Chester to Bucks counties then this collided with the ouflow moving northwestward from the storms in southern NJ. The added lift by these allowed new convection to develop and quickly form into a line before getting choked off. Interesting day!

well done.

love this capture

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I saw that on radar and witnessed it overhead! I live about 4 miles east of Lambertville and it was interesting to see happen. My wife coming home (from the east, from hopewell) encountered hail, 2 fallen trees on rt 518 and needed to pullover due to the intensity of the rainfall. I noticed that the sky kept getting darker and darker. Not the worst storm I experiencedsince moving in but interesting indeed.

Looks like my office and OKX basically requesting a watch box from SPC panned out fairly well this afternoon. Interestingly enough, the 12z SPC WRF actually had the convection exploding into a solid line across southeast PA then weaken as it moved into NJ. Based on radar loops posted earlier and latest radar trends, that is indeed what happened. Also on the radar loop posted earlier, impressive outflow boundary across Chester to Bucks counties then this collided with the ouflow moving northwestward from the storms in southern NJ. The added lift by these allowed new convection to develop and quickly form into a line before getting choked off. Interesting day!

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I saw that on radar and witnessed it overhead! I live about 4 miles east of Lambertville and it was interesting to see happen. My wife coming home (from the east, from hopewell) encountered hail, 2 fallen trees on rt 518 and needed to pullover due to the intensity of the rainfall. I noticed that the sky kept getting darker and darker. Not the worst storm I experiencedsince moving in but interesting indeed.

also, went into Lambertville to pick up dinner and York St was closed. Numerous firetrucks were on the street. Not sure if someone's house was unfortunatly hit by lightening or something

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SPC has a day 2 slight out for our area now, enhanced wording also.

...ERN NY/PA...MD/DE/NJ INTO SRN ME...

SHOWERS AND STORMS WILL BE ONGOING ALONG THE COLD FRONT EARLY IN THE

DAY ACROSS WRN NY/PA. AS THE ATMOSPHERE DESTABILIZES ACROSS THE WARM

SECTOR...ACTIVITY ALONG THE FRONT SHOULD REJUVENATE AND BECOME

SEVERE BY AFTERNOON. FORECAST SOUNDINGS SHOW VERY FAVORABLE DEEP

LAYER SHEAR PROFILES FOR SEVERE...INCLUDING DAMAGING WINDS AND LARGE

HAIL. WHILE FORCING WILL BE LINEAR ALONG THE FRONT...SHEAR PROFILE

ORIENTATION SUGGESTS THAT SUPERCELLS WILL BE LIKELY...PERHAPS SOME

SPLITTING GIVEN ONLY MODEST LOW LEVEL HODOGRAPH CURVATURE. MESOSCALE

DETAILS WILL DETERMINE TORNADO THREAT...WHICH MAY BE LOCALLY

ENHANCED ALONG THE RESIDUAL WARM FRONT WITH LOCALLY BACKED SURFACE

WINDS. HOWEVER...THE PRIMARY THREAT WILL BE HAIL AND WIND.

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Just before storm hit in West Chester, looking NW.

1.94" today

3.64" today and yesterday

6.11" last 7 days

Max rain rate of 11.29"/hr today (station record!).

Max wind - 23mph

I was in Royersford, and the sky also looked like it might produce a funnel. But just got caught in seemingly endless heavy rain and big lightning bolts.

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little excerpt from the spc on sundays svr risk

..ERN NY/PA...MD/DE/NJ INTO SRN ME... SHOWERS AND STORMS WILL BE ONGOING ALONG THE COLD FRONT EARLY IN THE DAY ACROSS WRN NY/PA. AS THE ATMOSPHERE DESTABILIZES ACROSS THE WARM SECTOR...ACTIVITY ALONG THE FRONT SHOULD REJUVENATE AND BECOME SEVERE BY AFTERNOON. FORECAST SOUNDINGS SHOW VERY FAVORABLE DEEP LAYER SHEAR PROFILES FOR SEVERE...INCLUDING DAMAGING WINDS AND LARGE HAIL. WHILE FORCING WILL BE LINEAR ALONG THE FRONT...SHEAR PROFILE ORIENTATION SUGGESTS THAT SUPERCELLS WILL BE LIKELY...PERHAPS SOME SPLITTING GIVEN ONLY MODEST LOW LEVEL HODOGRAPH CURVATURE. MESOSCALE DETAILS WILL DETERMINE TORNADO THREAT...WHICH MAY BE LOCALLY ENHANCED ALONG THE RESIDUAL WARM FRONT WITH LOCALLY BACKED SURFACE WINDS. HOWEVER...THE PRIMARY THREAT WILL BE HAIL AND WIND.

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little excerpt from the spc on sundays svr risk

..ERN NY/PA...MD/DE/NJ INTO SRN ME... SHOWERS AND STORMS WILL BE ONGOING ALONG THE COLD FRONT EARLY IN THE DAY ACROSS WRN NY/PA. AS THE ATMOSPHERE DESTABILIZES ACROSS THE WARM SECTOR...ACTIVITY ALONG THE FRONT SHOULD REJUVENATE AND BECOME SEVERE BY AFTERNOON. FORECAST SOUNDINGS SHOW VERY FAVORABLE DEEP LAYER SHEAR PROFILES FOR SEVERE...INCLUDING DAMAGING WINDS AND LARGE HAIL. WHILE FORCING WILL BE LINEAR ALONG THE FRONT...SHEAR PROFILE ORIENTATION SUGGESTS THAT SUPERCELLS WILL BE LIKELY...PERHAPS SOME SPLITTING GIVEN ONLY MODEST LOW LEVEL HODOGRAPH CURVATURE. MESOSCALE DETAILS WILL DETERMINE TORNADO THREAT...WHICH MAY BE LOCALLY ENHANCED ALONG THE RESIDUAL WARM FRONT WITH LOCALLY BACKED SURFACE WINDS. HOWEVER...THE PRIMARY THREAT WILL BE HAIL AND WIND.

<knock on wood> I'm pleased to have apparently ushered in all the weather to the region (well, except for the extra work that the Mt. Holly guys have had to do to keep up). Maybe this will be the grand finale (I leave Monday).

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Weather here the last 7 days:

8/12 85 58 0.00 (Davis tipping bucket 0.00)
8/13 86 61 0.13 (Davis tipping bucket 0.13)
8/14 72 67 4.84 (Davis tipping bucket 4.54)
8/15 78 65 0.82 (Davis tipping bucket 0.80)
8/16 78 67 0.18 (Davis tipping bucket 0.14)
8/17 88 63 0.00 (Davis tipping bucket 0.00)
8/18 86 67 0.35 (Davis tipping bucket 0.34)
8/19 86 66 0.72 (Davis tipping bucket 0.77)
Total rain:  7.04  (Davis tipping bucket 6.72)

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Not bad at all, SPC has our area in the slight risk, with 5/30/15 probs. Tornado/wind/hail.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1257 AM CDT SUN AUG 21 2011

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER OH VALLEY AND

MID ATLANTIC STATES INTO NEW ENGLAND...

...SYNOPSIS...

AN UPPER TROUGH CURRENTLY EXTENDING SWD THROUGH THE GREAT LAKES AND

ANCHORED BY A VORTEX OVER HUDSON BAY WILL UNDERGO FURTHER

AMPLIFICATION AS A SHORTWAVE TROUGH TRACKS ESEWD FROM THE UPPER

GREAT LAKES TO NY/PA THIS FORECAST PERIOD. AT 12Z SUNDAY...A COLD

FRONT ATTENDANT TO THE PARENT LONGWAVE TROUGH SHOULD EXTEND SWWD

FROM SRN ONTARIO THROUGH THE LOWER OH VALLEY TO CENTRAL AR AND WWD

INTO OK. THIS BOUNDARY WILL PROGRESS E/SEWD MOVING THROUGH MUCH OF

THE NERN AND MID-ATLANTIC STATES...AND EXTEND WSWWD INTO THE CENTRAL

GULF COAST STATES BY 12Z MONDAY.

FARTHER W...AN IMPULSE EMANATING FROM AN UPPER LOW ALONG THE NRN CA

COAST IS EXPECTED TO MOVE INTO WRN/NRN MT THIS AFTERNOON AIDING IN

SOME TSTM DEVELOPMENT OVER THE HIGHER TERRAIN. MEANWHILE...HEIGHT

RISES ARE EXPECTED ACROSS THE NRN HIGH PLAINS...TENDING TO LIMIT

TSTM DEVELOPMENT.

...MID-ATLANTIC STATES TO NEW ENGLAND...

00Z NAM/GFS AND 12Z ECMWF AGREE WITH THE TIMING OF THE COLD FRONT

TODAY...REACHING NRN NY TO WRN PA/UPPER OH VALLEY DURING THE

EARLY-MID AFTERNOON. GIVEN THE TIMING OF THE FRONT ALLOWING FOR

SURFACE HEATING/DESTABILIZATION AND THE ARRIVAL OF FORCING ALOFT

DURING THE AFTERNOON/EVENING...THE FORECAST CONFIDENCE REMAINS GOOD

FOR THE DEVELOPMENT OF SEVERE STORMS TODAY INTO TONIGHT ACROSS THE

SLIGHT RISK AREA. SWLY LOW LEVEL WINDS ACROSS THE OH VALLEY TO WRN

PA AND SSWLY LOW LEVEL WINDS IN LEE OF THE CENTRAL APPALACHIANS TO

THE HUDSON VALLEY/NEW ENGLAND WILL EACH SUPPORT MOISTURE ADVECTION

INTO THESE REGIONS. ALTHOUGH MIDLEVEL LAPSE RATES ARE FORECAST TO

BE MODEST /AOB 6.5 C PER KM/ ACROSS THE SLIGHT RISK AREA...SURFACE

HEATING COMBINED WITH THE MOISTURE RETURN WILL RESULT IN MODERATE

INSTABILITY FROM MD/D.C./DELMARVA TO SERN/ERN NY AND SWRN NEW

ENGLAND THIS AFTERNOON. MLCAPE ACROSS THIS CORRIDOR WILL BE UP TO

1500-2000 J/KG WHILE FURTHER W OVER THE UPPER OH VALLEY VALUES WILL

BE UP TO 1000 J/KG.

DIFFLUENT FLOW ALOFT AND HEIGHT FALLS WITH THE APPROACH OF THE UPPER

GREAT LAKES SHORTWAVE TROUGH...AND CONVERGENCE/ASCENT ALONG THE COLD

FRONT AND PRE-FRONTAL/LEE TROUGH EXTENDING FROM VA TO ERN NY WILL

SUPPORT TSTM DEVELOPMENT BY EARLY-MID AFTERNOON IN VICINITY AND

AHEAD OF THESE SURFACE BOUNDARIES. STRENGTHENING WIND FIELDS AND

EFFECTIVE BULK SHEAR OF 40-50 KT COMBINED WITH THE AVAILABLE

INSTABILITY WILL SUPPORT ORGANIZED STORMS. SHEAR VECTORS MORE

NORMAL TO THE LEE TROUGH SUGGEST A GREATER POTENTIAL FOR DISCRETE

STORMS...INCLUDING SUPERCELLS. VERTICALLY VEERING WINDS AND HIGHER

THETAE EXTENDING FROM MD/ERN PA TO SERN NY/SWRN NEW ENGLAND SUPPORT

AN ISOLATED TORNADO THREAT ALONG WITH DAMAGING WINDS AND HAIL.

FARTHER W INTO THE UPPER OH VALLEY...ORGANIZED STRONG TO SEVERE

STORMS WILL BE POSSIBLE BY EARLY-MID AFTERNOON WITH STRONG WIND

GUSTS AND HAIL THE PRIMARY THREATS.

ALTHOUGH INSTABILITY SHOULD BE WEAKENING THIS EVENING...A FURTHER

INCREASE IN DEEP LAYER WIND FIELDS INTO THE NERN STATES AND 60-90

METER HEIGHT FALLS ACROSS THIS REGION SHOULD COMPENSATE THE WEAKER

THERMODYNAMICS FOR AT LEAST A CONTINUED THREAT FOR DAMAGING WINDS

INTO PARTS OF NEW ENGLAND. FORECAST SOUNDINGS SUGGEST A TORNADO

CANNOT BE RULED OUT ACROSS SRN NEW ENGLAND AS STRENGTHENING SLY LLJ

SUPPORTS AN INCREASE IN LOW LEVEL HODOGRAPH CURVATURE.

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looks like an interesting day shaping up. I spend my time between the poconos and the NJ shore, southern monmouth and let me say this year thus far has been absolutely crazy when it comes to storms.

I have seen everything but rotation on the ground.

Good luck everyone and be safe on the chase!!

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