Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 300, NWS Philadelphia/Mount Holly

September 11, 2011Chester County, Delaware County, Philadelphia County, Pennsylvania; New Castle County, Delaware; Cumberland County, Gloucester County, Salem County, New Jersey

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Sep 11, 2011, 11:10 PM EDT for Chester County, Delaware County, Philadelphia County, Pennsylvania; New Castle County, Delaware; Cumberland County, Gloucester County, Salem County, New Jersey. It was in force for 65 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, 11:10 PM EDT (03:10 UTC)
Expired: Sep 12, 2011, 12:15 AM EDT
In force: 65 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties New Castle County, DE, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Chester County, PA, Delaware County, PA, Philadelphia County, PA

The radar

The Dover AFB radar (KDOX), 82 km from the middle of the area, began a volume at 03:10 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, 11:15 PM EDT	TSTM WND DMG	Drexel Hill, PA	TREE LIMBS DOWN.

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, 3.2 hours before the alert went out and 177 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.

788 
WUUS51 KPHI 120310
SVRPHI
DEC003-NJC011-015-033-PAC029-045-101-120415-
/O.NEW.KPHI.SV.W.0300.110912T0310Z-110912T0415Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1110 PM EDT SUN SEP 11 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITIES OF...WILMINGTON...MIDDLETOWN...
  EAST CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...
  DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA...
  SOUTHWESTERN PHILADELPHIA COUNTY IN SOUTHEAST PENNSYLVANIA...
  NORTHWESTERN CUMBERLAND COUNTY IN SOUTHERN NEW JERSEY...
  WESTERN GLOUCESTER COUNTY IN SOUTHERN NEW JERSEY...
  SALEM COUNTY IN SOUTHERN NEW JERSEY...

* UNTIL 1215 AM EDT

* AT 1105 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  LINE OF SEVERE THUNDERSTORMS.  THESE STORMS WERE LOCATED ALONG A
  LINE EXTENDING FROM WEST CHESTER TO MIDDLETOWN...AND MOVING EAST AT
  20 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  WESTTOWN...CHEYNEY...ELAM AND WILMINGTON MANOR AROUND 1115 PM
  EDT...
  CONCORDVILLE...PORT PENN...WILMINGTON AND NEW CASTLE AROUND 1120 PM
  EDT...
  GRADYVILLE AND CHELSEA AROUND 1125 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 GREATEST KILLERS. REMEMBER...IF YOU CAN HEAR 
THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.

HEAVY RAIN WILL OCCUR WITH THESE STORMS AND CAUSE LOW-LYING AND 
POOR DRAINAGE FLOODING.

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 3999 7567 3998 7528 4000 7513 3935 7525
      3934 7539 3943 7548 3945 7554 3950 7557
      3952 7554 3957 7553 3958 7556 3946 7558
      3942 7553 3937 7550 3933 7557 3931 7577
TIME...MOT...LOC 0309Z 280DEG 19KT 3992 7558 3941 7568

$$

MPD

1 follow-up statement

316 
WWUS51 KPHI 120336
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1136 PM EDT SUN SEP 11 2011

PAC029-120346-
/O.CAN.KPHI.SV.W.0300.000000T0000Z-110912T0415Z/
CHESTER PA-
1136 PM EDT SUN SEP 11 2011

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL CHESTER COUNTY 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 3974 7570 3984 7562 3984 7560 3986 7561
      3992 7556 3992 7553 3997 7548 4000 7513
      3935 7525 3934 7539 3943 7548 3945 7554
      3950 7557 3957 7553 3958 7556 3946 7558
      3937 7550 3933 7557 3931 7576
TIME...MOT...LOC 0336Z 280DEG 19KT 3989 7540 3938 7550

$$

DEC003-NJC011-015-033-PAC045-101-120415-
/O.CON.KPHI.SV.W.0300.000000T0000Z-110912T0415Z/
SALEM NJ-CUMBERLAND NJ-GLOUCESTER NJ-DELAWARE PA-PHILADELPHIA PA-
NEW CASTLE DE-
1136 PM EDT SUN SEP 11 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1215 AM EDT
FOR NEW CASTLE...SOUTHWESTERN PHILADELPHIA...DELAWARE...WESTERN
GLOUCESTER...NORTHWESTERN CUMBERLAND AND SALEM COUNTIES...

AT 1131 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO 
INDICATE SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN 
EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE EXTENDING 
FROM LIMA TO CHAMBERSVILLE...OR ALONG A LINE EXTENDING FROM 10 MILES 
SOUTHEAST OF WEST CHESTER TO 11 MILES EAST OF MIDDLETOWN...MOVING 
EAST AT 20 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  FOLSOM...SWARTHMORE...RUTLEDGE AND MORTON BY 1145 PM EDT...
  PROSPECT PARK...NORWOOD...GLENOLDEN AND COLLINGDALE BY 1150 PM
  EDT...
  PHILADELPHIA INTERNATIONAL AIRPORT AND FOLCROFT BY 1155 PM EDT...

OTHER STRONG STORMS WERE TRAILING THE LINE AND ENTERING NEW CASTLE 
COUNTY. 

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 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 3974 7570 3984 7562 3984 7560 3986 7561
      3992 7556 3992 7553 3997 7548 4000 7513
      3935 7525 3934 7539 3943 7548 3945 7554
      3950 7557 3957 7553 3958 7556 3946 7558
      3937 7550 3933 7557 3931 7576
TIME...MOT...LOC 0336Z 280DEG 19KT 3989 7540 3938 7550

$$

MPD

The office that day

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

Issued	Product	Office	Counties	Lasted
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, 10:29 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	46 min
Sep 11, 10:44 PM EDT	Areal Flood Advisory	PHI	Chester	107 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, 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 12, 12:46 AM EDT	Special Weather Statement	PHI	Kent	59 min
Sep 11, 11:15 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Monmouth, Ocean	60 min
Sep 12, 12:17 AM EDT	Special Weather Statement	PHI	Ocean	58 min
Sep 12, 12:24 AM EDT	Severe Thunderstorm Warning	PHI	Ocean	66 min
Sep 12, 12:34 AM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Camden, Cumberland, Gloucester, Salem	56 min
Sep 12, 1:29 AM EDT	Special Weather Statement	PHI	Atlantic, Burlington, Cumberland, Ocean	61 min
Sep 12, 1:33 AM EDT	Special Marine Warning	PHI		117 min
Sep 12, 2:15 PM EDT	Special Weather Statement	PHI	Sussex	60 min
Sep 12, 3:59 PM EDT	Special Weather Statement	PHI	Morris	91 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2011 Severe Thunderstorm Warnings in New Jersey, 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.