Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 221, NWS Philadelphia/Mount Holly

August 1, 20115 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 1, 2011, 4:33 PM EDT for 5 counties in Pennsylvania. It was in force for 87 min. 3 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 1, 2011, 4:33 PM EDT (20:33 UTC)
Expired: Aug 1, 2011, 6:00 PM EDT
In force: 87 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Berks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 77 km from the middle of the area, began a volume at 20:34 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Aug 1, 4:55 PM EDT	TSTM WND DMG	King Of Prussia, PA	TREES DOWN IN KING OF PRUSSIA.
Aug 1, 5:49 PM EDT	HAIL 0.75	Drexel Hill, PA	PEA UP TO PENNY SIZE HAIL REPORTED IN DREXEL HILL.
Aug 1, 5:53 PM EDT	HAIL 1	Sharon Hill, PA	NICKEL UP TO QUARTER SIZE HAIL REPORTED IN SHARON HILL.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 8.6 hours before the alert went out and 95 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 307 J/kg
Mixed-layer CIN: -150 J/kg
Mixed-layer LCL: 1512 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: -192 m²/s²
0-3 km storm-relative helicity: -166 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -1.5

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

043 
WUUS51 KPHI 012033
SVRPHI
PAC011-029-045-091-101-012200-
/O.NEW.KPHI.SV.W.0221.110801T2033Z-110801T2200Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
433 PM EDT MON AUG 1 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  SOUTHEASTERN BERKS COUNTY IN EASTERN PENNSYLVANIA...
  NORTHEASTERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  NORTHEASTERN DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA...
  MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA...
  PHILADELPHIA COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF PHILADELPHIA...

* UNTIL 600 PM EDT

* AT 430 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED 6 MILES
  NORTHWEST OF CEDARVILLE...OR 10 MILES EAST OF READING...AND  
  MOVING SOUTHEAST AT 20 MPH. THERE WERE OTHER INTENSIFYING STORMS
  THAT ALSO COULD BECOME SEVERE NEAR COLLEGEVILLE AND OVER THE CITY
  OF PHILADELPHIA.
 
* THE SEVERE THUNDERSTORM WILL BE NEAR...
  POTTSTOWN AND CEDARVILLE AROUND 450 PM EDT...
  POTTSTOWN AROUND 455 PM EDT...
  PUGHTOWN AROUND 500 PM EDT...
  ROYERSFORD AROUND 515 PM EDT...
  TRAPPE AND PHOENIXVILLE AROUND 525 PM EDT...
  COLLEGEVILLE AROUND 530 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS...DESTRUCTIVE HAIL...AND DEADLY CLOUD
TO GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...
PREFERABLY INSIDE A STRONG BUILDING BUT AWAY FROM WINDOWS.

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.

&&

LAT...LON 4021 7586 4044 7554 4009 7496 4004 7500
      3997 7509 3998 7511 3995 7514 3994 7515
      3985 7527
TIME...MOT...LOC 2032Z 303DEG 15KT 4029 7574

$$

TFG

1 follow-up statement

319 
WWUS51 KPHI 012119
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
519 PM EDT MON AUG 1 2011

PAC011-012128-
/O.CAN.KPHI.SV.W.0221.000000T0000Z-110801T2200Z/
BERKS PA-
519 PM EDT MON AUG 1 2011

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN BERKS COUNTY IS
CANCELLED...

THE SEVERE STORMS HAVE MOVED INTO MONTGOMERY COUNTY.

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.

LAT...LON 4004 7500 4000 7505 3997 7509 3998 7511
      3994 7515 3985 7527 4020 7567 4031 7554
      4006 7499
TIME...MOT...LOC 2118Z 303DEG 15KT 4022 7554 4001 7524

$$

PAC029-045-091-101-012200-
/O.CON.KPHI.SV.W.0221.000000T0000Z-110801T2200Z/
DELAWARE PA-PHILADELPHIA PA-CHESTER PA-MONTGOMERY PA-
519 PM EDT MON AUG 1 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 PM EDT
FOR SOUTHERN MONTGOMERY...NORTHEASTERN CHESTER...PHILADELPHIA AND
NORTHEASTERN DELAWARE COUNTIES...

AT 513 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING QUARTER
SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.  THESE STORMS
WERE LOCATED ALONG A LINE EXTENDING FROM SANATOGA TO NARBERTH...OR
ALONG A LINE EXTENDING FROM 19 MILES NORTH OF WEST CHESTER TO 7 MILES
WEST OF PHILADELPHIA...MOVING SOUTHEAST AT 15 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  SCHWENKSVILLE...SPRING MOUNT...ROXBOROUGH AND PROSPECT PARK BY 525
  PM EDT...
  TRAPPE...SHARON HILL...FOLCROFT AND DARBY TOWNSHIP BY 530 PM EDT...
  COLLEGEVILLE AND PHILADELPHIA INTERNATIONAL AIRPORT BY 535 PM
  EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM HAS A HISTORY OF PRODUCING WIND DAMAGE IN MONTGOMERY
COUNTY AND HAIL. SEEK SHELTER NOW INSIDE A STURDY STRUCTURE AND STAY
AWAY FROM WINDOWS!

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.

&&

LAT...LON 4004 7500 4000 7505 3997 7509 3998 7511
      3994 7515 3985 7527 4020 7567 4031 7554
      4006 7499
TIME...MOT...LOC 2118Z 303DEG 15KT 4022 7554 4001 7524

$$

TFG

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 31, 10:00 PM EDT	Special Weather Statement	PHI	Chester	60 min
Aug 1, 1:35 PM EDT	Special Weather Statement	PHI	Carbon, Lehigh, Monroe, Northampton	3 hr
Aug 1, 3:14 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	51 min
Aug 1, 3:46 PM EDT	Special Weather Statement	PHI	Berks	89 min
Aug 1, 4:00 PM EDT	Severe Thunderstorm Warning	PHI	Berks	75 min
Aug 1, 4:39 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Lehigh	42 min
Aug 1, 5:11 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	2 hr
Aug 1, 5:37 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Philadelphia	53 min
Aug 1, 5:50 PM EDT	Severe Thunderstorm Warning	PHI	Philadelphia	70 min
Aug 1, 6:17 PM EDT	Areal Flood Advisory	PHI	Delaware, Philadelphia	3 hr
Aug 1, 6:20 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	46 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2011 Every severe thunderstorm warning in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.