Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 299, NWS Philadelphia/Mount Holly

September 11, 2011New Castle County, Delaware; Chester County, Delaware County, Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Sep 11, 2011, 10:29 PM EDT for New Castle County, Delaware; Chester County, Delaware County, Pennsylvania; Cecil County, Maryland. It was in force for 46 min. 1 report 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: Sep 11, 2011, 10:29 PM EDT (02:29 UTC)
Expired: Sep 11, 2011, 11:15 PM EDT
In force: 46 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

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

The radar

The Dover AFB radar (KDOX), 113 km from the middle of the area, began a volume at 02:32 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
Sep 11, 10:45 PM EDT	HAIL 1	Newark, DE

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 2.5 hours before the alert went out and 154 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: 420 J/kg
Mixed-layer CIN: -58 J/kg
Mixed-layer LCL: 1369 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 144 m²/s²
0-3 km storm-relative helicity: 126 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.

145 
WUUS51 KPHI 120229
SVRPHI
DEC003-MDC015-PAC029-045-120315-
/O.NEW.KPHI.SV.W.0299.110912T0229Z-110912T0315Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1029 PM EDT SUN SEP 11 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...
  NORTHWESTERN NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITY OF NEWARK...
  SOUTHERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...
  SOUTHWESTERN DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 1115 PM EDT

* AT 1026 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
  EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE EXTENDING
  FROM PARKESBURG TO NORTH EAST...OR ALONG A LINE EXTENDING FROM 16
  MILES WEST OF WEST CHESTER TO 8 MILES WEST OF ELKTON...AND MOVING
  EAST AT 20 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  PLEASANT HILL AROUND 1035 PM EDT...
  COATESVILLE...FAIR HILL...ANDORA AND WEST GROVE AROUND 1040 PM
  EDT...
  KEMBLESVILLE AND CHERRY HILL AROUND 1045 PM EDT...
  LADENBERG...GLEN WESTOVER AND BRANTWOOD AROUND 1050 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IN ADDITION TO DAMAGING WINDS...DANGEROUS CLOUD TO GROUND LIGHTNING 
IS OCCURRING WITH THESE STORMS. MOVE INDOORS IMMEDIATELY! LIGHTNING 
IS ONE OF NATURES GREATEST KILLERS. REMEMBER...IF YOU CAN HEAR 
THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.

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 3986 7603 3987 7601 3992 7601 3993 7600
      3996 7600 4004 7595 4009 7551 3948 7562
      3951 7599 3953 7600 3955 7603 3954 7607
      3956 7610
TIME...MOT...LOC 0228Z 261DEG 19KT 3996 7589 3961 7596

$$

1 follow-up statement

955 
WWUS51 KPHI 120257
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1057 PM EDT SUN SEP 11 2011

DEC003-MDC015-PAC029-045-120315-
/O.CON.KPHI.SV.W.0299.000000T0000Z-110912T0315Z/
CECIL MD-DELAWARE PA-CHESTER PA-NEW CASTLE DE-
1057 PM EDT SUN SEP 11 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1115 PM EDT
FOR NORTHWESTERN NEW CASTLE...SOUTHERN CHESTER...SOUTHWESTERN
DELAWARE AND NORTHEASTERN CECIL COUNTIES...

AT 1053 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING
WINDS IN EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE
EXTENDING FROM DOWNINGTOWN TO CHESAPEAKE CITY...OR ALONG A LINE
EXTENDING FROM 6 MILES WEST OF WEST CHESTER TO 6 MILES NORTHWEST OF
MIDDLETOWN...MOVING EAST AT 20 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  LIONVILLE...MOUNT PLEASANT...HOCKESSIN AND ASHLAND BY 1105 PM
  EDT...
  EXTON...BEAR...WEST CHESTER AND STANTON BY 1110 PM EDT...
  SAINT GEORGES AND WEST GOSHEN BY 1115 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IN ADDITION TO DAMAGING WINDS...DANGEROUS CLOUD TO GROUND LIGHTNING 
IS OCCURRING WITH THIS STORM. MOVE INDOORS IMMEDIATELY! LIGHTNING IS 
ONE OF NATURES NUMBER ONE KILLERS. REMEMBER...IF YOU CAN HEAR 
THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.

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 3954 7582 3955 7586 3957 7587 3962 7591
      3968 7589 3981 7587 3982 7582 3987 7585
      3992 7589 3995 7588 4002 7580 4009 7551
      3948 7562 3950 7581
TIME...MOT...LOC 0257Z 261DEG 19KT 3998 7569 3951 7578

$$

MPD

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 11, 10:44 PM EDT	Areal Flood Advisory	PHI	New Castle	107 min
Sep 11, 11:02 PM EDT	Areal Flood Advisory	PHI	Kent, New Castle	103 min
Sep 11, 11:05 PM EDT	Special Weather Statement	PHI	New Castle	85 min
Sep 11, 11:10 PM EDT	Severe Thunderstorm Warning	PHI	New Castle	65 min
Sep 12, 12:46 AM EDT	Special Weather Statement	PHI	Kent	59 min
Sep 11, 8:19 PM EDT	Flash Flood Warning	PHI	Berks	3 hr
Sep 11, 8:46 PM EDT	Areal Flood Advisory	PHI	Chester	3 hr
Sep 11, 9:00 PM EDT	Flash Flood Warning	PHI	Chester	3 hr
Sep 11, 9:14 PM EDT	Flash Flood Warning	PHI	Berks, Chester, Montgomery	110 min
Sep 11, 9:14 PM EDT	Special Weather Statement	PHI	Berks, Chester, Lehigh, Montgomery	61 min
Sep 11, 9:24 PM EDT	Severe Thunderstorm Warning	PHI	Chester	51 min
Sep 11, 9:34 PM EDT	Special Weather Statement	PHI	Philadelphia	41 min
Sep 11, 9:54 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	51 min
Sep 11, 9:56 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	4 hr
Sep 11, 10:25 PM EDT	Special Weather Statement	PHI	Philadelphia	65 min
Sep 11, 10:52 PM EDT	Special Weather Statement	PHI	Bucks, Delaware, Montgomery, Philadelphia	83 min
Sep 12, 11:05 AM EDT	Coastal Flood Statement	PHI	Delaware, Philadelphia	6 hr
Sep 11, 10:08 PM EDT	Special Weather Statement	PHI	Cecil	67 min

Nearby

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