Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 246, NWS Philadelphia/Mount Holly

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

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 18, 2011, 5:48 PM EDT for Chester County, Pennsylvania; Cecil County, Maryland; New Castle County, Delaware. It was in force for 57 min. 5 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, 5:48 PM EDT (21:48 UTC)
Expired: Aug 18, 2011, 6:45 PM EDT
In force: 57 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties New Castle County, DE, Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 101 km from the middle of the area, began a volume at 21:49 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
Aug 18, 6:05 PM EDT	HAIL 1	Port Deposit, MD
Aug 18, 6:10 PM EDT	HAIL 1	Perryville, MD
Aug 18, 6:25 PM EDT	HAIL 0.75	North East, MD
Aug 18, 6:30 PM EDT	HAIL 0.5	Oxford, PA
Aug 18, 6:45 PM EDT	HAIL 0.5	Newark, DE

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, 9.8 hours before the alert went out and 19 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.

179 
WUUS51 KPHI 182148
SVRPHI
DEC003-MDC015-PAC029-182245-
/O.NEW.KPHI.SV.W.0246.110818T2148Z-110818T2245Z/

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

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NORTHERN CECIL COUNTY IN NORTHEAST MARYLAND...
  THIS INCLUDES THE CITY OF ELKTON...
  WEST CENTRAL NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITY OF NEWARK...
  SOUTHWESTERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 645 PM EDT

* AT 546 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 8 MILES
  SOUTHWEST OF OCTORARO...OR 22 MILES WEST OF ELKTON...AND MOVING
  NORTHEAST AT 20 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  OCTORARO AROUND 605 PM EDT...
  WOODLAWN AND RICHARDSMERE AROUND 615 PM EDT...
  WEST NOTTINGHAM AND CHARLESTOWN AROUND 620 PM EDT...
  FARMINGTON AND RISING SUN AROUND 625 PM EDT...
  BAY VIEW AND NORTH EAST AROUND 630 PM EDT...
  ZION AROUND 635 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 3990 7587 3962 7565 3948 7598 3950 7601
      3951 7599 3953 7599 3955 7603 3954 7607
      3962 7616 3965 7617 3968 7622
TIME...MOT...LOC 2148Z 239DEG 17KT 3955 7621

$$

HEAVENER

2 follow-up statements

613 
WWUS51 KPHI 182237
SVSPHI

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

DEC003-MDC015-PAC029-182245-
/O.CON.KPHI.SV.W.0246.000000T0000Z-110818T2245Z/
CECIL MD-CHESTER PA-NEW CASTLE DE-
637 PM EDT THU AUG 18 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 645 PM EDT
FOR WEST CENTRAL NEW CASTLE...SOUTHWESTERN CHESTER AND NORTHERN CECIL
COUNTIES...

AT 633 PM EDT...THE PUBLIC REPORTED A SEVERE THUNDERSTORM CAPABLE OF
PRODUCING QUARTER SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.
 THIS STORM WAS LOCATED NEAR ZION...OR 9 MILES NORTHWEST OF ELKTON...
MOVING NORTHEAST AT 20 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  BLAKE...FAIR HILL...ANDORA AND CHERRY HILL BY 645 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HAIL UP TO 1.25 INCHES IN DIAMETER HAS BEEN REPORTED IN PORT DEPOSIT 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 3951 7594 3962 7611 3969 7620 3990 7587
      3962 7565
TIME...MOT...LOC 2237Z 239DEG 17KT 3967 7595

$$

HEAVENER

048 
WWUS51 KPHI 182245
SVSPHI

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

DEC003-MDC015-PAC029-182255-
/O.EXP.KPHI.SV.W.0246.000000T0000Z-110818T2245Z/
CECIL MD-CHESTER PA-NEW CASTLE DE-
645 PM EDT THU AUG 18 2011

...THE SEVERE THUNDERSTORM WARNING FOR WEST CENTRAL NEW CASTLE...
SOUTHWESTERN CHESTER AND NORTHERN CECIL COUNTIES HAS EXPIRED...

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 3951 7594 3962 7611 3969 7620 3990 7587
      3962 7565
TIME...MOT...LOC 2237Z 239DEG 17KT 3967 7595

$$

HEAVENER

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, 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, 7:14 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	50 min
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, 6:04 PM EDT	Areal Flood Advisory	PHI	Cecil	116 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 Maryland, 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.