Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2004

Severe Thunderstorm Warning 203, NWS Philadelphia/Mount Holly

September 28, 2004Chester County, Delaware County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Sep 28, 2004, 4:41 PM EDT for Chester County, Delaware County, Pennsylvania; New Castle County, Delaware. It was in force for 79 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Sep 28, 2004, 4:41 PM EDT (20:41 UTC)
Expired
Sep 28, 2004, 6:00 PM EDT
In force
79 min
Issued by
NWS Philadelphia/Mount Holly
Area
Counties, with a storm outline in the text

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

The radar

The Philadelphia radar (KDIX), 100 km from the middle of the area, began a volume at 20:41 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.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

IssuedProductOfficeLasted
Sep 28, 2:25 PM EDTTornado WatchSPC7 hr

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 8.7 hours before the alert went out and 68 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-pSkew-T log-p diagram, Phillips Aaf/Abe, MD at 12:00Z on 2004-09-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 95 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Phillips Aaf/Abe, MD at 12:00Z on 2004-09-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 109 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
95 J/kg
Mixed-layer CIN
-78 J/kg
Mixed-layer LCL
631 m above ground
0-6 km bulk shear
41 kt
0-1 km storm-relative helicity
109 m²/s²
0-3 km storm-relative helicity
172 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.4

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 282043
SVRPHI
DEC003-PAC029-045-282200-
/X.NEW.KPHI.SV.W.0007.040928T2041Z-040928T2200Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
441 PM EDT TUE SEP 28 2004

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  EAST CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA
  WESTERN DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA
  NORTHERN NEW CASTLE COUNTY IN DELAWARE
 
* UNTIL 600 PM EDT

* AT 437 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM.  THIS STORM WAS LOCATED 8 MILES SOUTHEAST OF
  KENNETT SQUARE...OR ABOUT NEAR WILMINGTON...AND MOVING NORTH AT 20
  MPH. THIS TORNADO PRODUCED A LIKELY TORNADO NEAR NEW CASTLE COUNTY
  AIRPORT. SINCE THEN THE STORM HAS WEAKENED...BUT DAMAGING WINDS
  ARE STILL POSSIBLE.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  6 MILES EAST OF KENNETT SQUARE BY 450 PM EDT
  WEST CHESTER AND 7 MILES WEST OF LIMA BY 515 PM EDT
  PAOLI AND 6 MILES EAST OF LIONVILLE BY 535 PM EDT

DOPPLER RADAR HAS INDICATED SOME WEAK ROTATION WITHIN THIS STORM.
WHILE NOT IMMEDIATELY LIKELY...A TORNADO MAY STILL DEVELOP. IF A
TORNADO IS SPOTTED...ACT QUICKLY AND MOVE TO A PLACE OF SAFETY IN A
STURDY STRUCTURE...SUCH AS A BASEMENT OR SMALL INTERIOR ROOM.

LAT...LON 4003 7538 3983 7546 3985 7554 3985 7564
      3980 7572 3980 7572 4003 7568 4004 7567
      4008 7567

$$

TFG

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 28, 12:48 PM EDTFlash Flood WarningPHIMonroe, Northampton3 hr
Sep 28, 3:55 PM EDTFlash Flood WarningPHIChester, Delaware3 hr
Sep 28, 4:16 PM EDTFlash Flood WarningPHIBerks, Bucks, Lehigh, Montgomery, Northampton3 hr
Sep 28, 4:55 PM EDTFlash Flood WarningPHICarbon, Monroe4 hr
Sep 28, 5:11 PM EDTFlash Flood WarningPHIPhiladelphia3 hr
Sep 28, 6:05 PM EDTSpecial Marine WarningPHI115 min
Sep 28, 6:47 PM EDTFlash Flood WarningPHIChester, Delaware3 hr
Sep 28, 7:11 PM EDTFlash Flood WarningPHIBerks, Bucks, Lehigh, Montgomery, Northampton6 hr
Sep 28, 2:12 PM EDTSevere Thunderstorm WarningPHINew Castle63 min
Sep 28, 2:36 PM EDTFlash Flood WarningPHIKent, New Castle3 hr
Sep 28, 3:14 PM EDTSevere Thunderstorm WarningPHINew Castle46 min
Sep 28, 4:01 PM EDTSevere Thunderstorm WarningPHINew Castle44 min
Sep 28, 4:11 PM EDTTornado WarningPHINew Castle34 min
Sep 28, 5:30 PM EDTFlash Flood WarningPHIKent, New Castle, Sussex3 hr

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2004Severe Thunderstorm Warnings in Delaware, 2004Every severe thunderstorm warning in 2004

Sources

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