Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 248, NWS Philadelphia/Mount Holly

August 18, 2011Chester County, Delaware County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 18, 2011, 7:14 PM EDT for Chester County, Delaware County, Pennsylvania; New Castle County, Delaware. It was in force for 50 min. 2 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 18, 2011, 7:14 PM EDT (23:14 UTC)
Expired: Aug 18, 2011, 8:04 PM EDT
In force: 50 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties New Castle County, DE, Chester County, PA, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 85 km from the middle of the area, began a volume at 23:15 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 18, 7:30 PM EDT	HAIL 0.88	West Chester, PA
Aug 18, 7:55 PM EDT	HAIL 0.5	Broomall, PA

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, 11.2 hours before the alert went out and 83 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: 780 J/kg
Mixed-layer CIN: -64 J/kg
Mixed-layer LCL: 1022 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 83 m²/s²
0-3 km storm-relative helicity: 143 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

221 
WUUS51 KPHI 182314
SVRPHI
DEC003-PAC029-045-190015-
/O.NEW.KPHI.SV.W.0248.110818T2314Z-110819T0015Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
714 PM EDT THU AUG 18 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NORTHEASTERN NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  EAST CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...
  DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 815 PM EDT

* AT 711 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 NEAR
  MARSHALLTON...OR NEAR WEST CHESTER...AND MOVING NORTHEAST AT 15
  MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  WEST CHESTER AROUND 725 PM EDT...
  WEST CHESTER AND ELAM AROUND 730 PM EDT...
  WESTTOWN AND CONCORDVILLE AROUND 735 PM EDT...
  CHEYNEY AROUND 740 PM EDT...
  GRADYVILLE AROUND 750 PM EDT...
  GRADYVILLE AND LIMA AROUND 755 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 4008 7542 4007 7541 4007 7537 4001 7534
      4002 7532 4001 7531 3991 7525 3988 7527
      3978 7561 3998 7570
TIME...MOT...LOC 2314Z 246DEG 13KT 3990 7564

$$

HEAVENER

2 follow-up statements

119 
WWUS51 KPHI 182355
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
755 PM EDT THU AUG 18 2011

DEC003-190004-
/O.CAN.KPHI.SV.W.0248.000000T0000Z-110819T0015Z/
NEW CASTLE DE-
755 PM EDT THU AUG 18 2011

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN NEW CASTLE 
COUNTY IS CANCELLED WHILE THE SOUTHEASTERN PORTION OF THE COUNTY 
STILL HAS AN ACTIVE WARNING...

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 4001 7560 4008 7542 4007 7541 4007 7537
      4001 7534 4002 7532 4001 7531 3991 7525
      3989 7527 3982 7546 3984 7553
TIME...MOT...LOC 2354Z 246DEG 13KT 3996 7547

$$

PAC029-045-190015-
/O.CON.KPHI.SV.W.0248.000000T0000Z-110819T0015Z/
DELAWARE PA-CHESTER PA-
755 PM EDT THU AUG 18 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM EDT
FOR EAST CENTRAL CHESTER AND DELAWARE COUNTIES...

AT 753 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE
HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS
LOCATED NEAR GRADYVILLE...OR 7 MILES EAST OF WEST CHESTER...MOVING
NORTHEAST AT 15 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  UPPER PROVIDENCE TOWNSHIP AND MEDIA BY 805 PM EDT...
  NEWTOWN SQUARE AND DEVON-BERWYN BY 810 PM EDT...
  TROUT LAKE...BROOMALL AND RADNOR TOWNSHIP BY 815 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HAIL UP TO 1 INCH IN DIAMETER HAS BEEN REPORTED
IN BOOTHWYN WITH THIS STORM. IF YOU ARE IN THE PATH OF
THE STORM...TAKE IMMEDIATE ACTION TO PROTECT LIFE AND PROPERTY.

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 4001 7560 4008 7542 4007 7541 4007 7537
      4001 7534 4002 7532 4001 7531 3991 7525
      3989 7527 3982 7546 3984 7553
TIME...MOT...LOC 2354Z 246DEG 13KT 3996 7547

$$

HEAVENER

608 
WWUS51 KPHI 190004
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
804 PM EDT THU AUG 18 2011

PAC029-045-190014-
/O.CAN.KPHI.SV.W.0248.000000T0000Z-110819T0015Z/
DELAWARE PA-CHESTER PA-
804 PM EDT THU AUG 18 2011

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL CHESTER AND
DELAWARE COUNTIES IS CANCELLED...

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 4001 7560 4008 7542 4007 7541 4007 7537
      4001 7534 4002 7532 4001 7531 3991 7525
      3989 7527 3982 7546 3984 7553
TIME...MOT...LOC 0004Z 246DEG 13KT 3997 7543

$$

IOVINO

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 2:57 AM EDT	Special Weather Statement	PHI	Berks	63 min
Aug 18, 3:53 AM EDT	Special Weather Statement	PHI	Berks	52 min
Aug 18, 4:48 AM EDT	Special Weather Statement	PHI	Chester, Montgomery	57 min
Aug 18, 5:45 AM EDT	Special Weather Statement	PHI	Delaware, Montgomery, Philadelphia	60 min
Aug 18, 6:04 AM EDT	Special Weather Statement	PHI	Berks, Chester	41 min
Aug 18, 6:35 AM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	3 hr
Aug 18, 7:29 AM EDT	Special Weather Statement	PHI	Bucks, Delaware, Montgomery, Philadelphia	61 min
Aug 18, 8:16 AM EDT	Special Weather Statement	PHI	Philadelphia	59 min
Aug 18, 9:29 AM EDT	Areal Flood Advisory	PHI	Delaware	2 hr
Aug 18, 3:12 PM EDT	Flash Flood Watch	PHI	Berks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more	29 hr
Aug 18, 5:30 PM EDT	Special Weather Statement	PHI	Monroe	60 min
Aug 18, 5:48 PM EDT	Severe Thunderstorm Warning	PHI	Chester	57 min
Aug 18, 6:18 PM EDT	Special Weather Statement	PHI	Chester	57 min
Aug 18, 6:39 PM EDT	Severe Thunderstorm Warning	PHI	Chester	66 min
Aug 18, 6:59 PM EDT	Flash Flood Warning	PHI	Chester	2 hr
Aug 18, 7:28 PM EDT	Special Weather Statement	PHI	Chester	62 min
Aug 18, 7:31 PM EDT	Special Weather Statement	PHI	Monroe	59 min
Aug 18, 7:37 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	53 min
Aug 18, 7:47 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe, Northampton	3 hr
Aug 18, 7:58 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	31 min
Aug 18, 7:59 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	61 min
Aug 18, 6:44 PM EDT	Special Weather Statement	PHI	New Castle	61 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2011 Severe Thunderstorm Warnings in Delaware, 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.