Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2007

Severe Thunderstorm Warning 120, NWS Philadelphia/Mount Holly

July 4, 2007Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 4, 2007, 8:47 PM EDT for Chester County, Pennsylvania. It was in force for 58 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
Jul 4, 2007, 8:47 PM EDT (00:47 UTC)
Expired
Jul 4, 2007, 9:45 PM EDT
In force
58 min
Issued by
NWS Philadelphia/Mount Holly
Area
Counties, with a storm outline in the text

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 128 km from the middle of the area, began a volume at 00:50 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
Jul 4, 2:06 PM EDTTornado WatchSPC8 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 0.8 hours before the alert went out and 175 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, Washington/Dulle, VA at 00:00Z on 2007-07-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1453 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2007-07-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 200 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
1453 J/kg
Mixed-layer CIN
-38 J/kg
Mixed-layer LCL
1011 m above ground
0-6 km bulk shear
27 kt
0-1 km storm-relative helicity
200 m²/s²
0-3 km storm-relative helicity
387 m²/s²
Significant tornado parameter
1.6
Supercell composite
13.3

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 050047
SVRPHI
PAC029-050145-
/O.NEW.KPHI.SV.W.0120.070705T0047Z-070705T0145Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
847 PM EDT WED JUL 4 2007

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 945 PM EDT

* AT 846 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING PENNY SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED 7 MILES
  SOUTHWEST OF HONEY BROOK...OR ABOUT 15 MILES EAST OF LANCASTER...
  AND MOVING EAST AT 30 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  HONEY BROOK BY 855 PM EDT...
  PARKESBURG BY 900 PM EDT...
  COATESVILLE BY 910 PM EDT...
  DOWNINGTOWN BY 920 PM EDT...
  7 MILES SOUTH OF LIONVILLE AND 8 MILES NORTH OF KENNETT SQUARE BY
  925 PM EDT...
  WEST CHESTER BY 930 PM EDT...

A TORNADO WATCH REMAINS IN EFFECT FOR THE WARNED AREA. 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 4015 7610 3997 7617 3982 7571 4007 7549

$$

MPD
1 follow-up statement
000 
WWUS51 KPHI 050116
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
915 PM EDT WED JUL 4 2007

PAC029-050145-
/O.CON.KPHI.SV.W.0120.000000T0000Z-070705T0145Z/
CHESTER PA-
915 PM EDT WED JUL 4 2007

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 945 PM EDT
FOR CENTRAL CHESTER COUNTY...

AT 911 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING PENNY SIZE 
HAIL...DANGEROUS CLOUD TO GROUND LIGHTNING...AND DAMAGING WINDS IN 
EXCESS OF 60 MPH.  THIS STORM WAS LOCATED NEAR SOUTH 
COATESVILLE...OR ABOUT 20 MILES NORTH OF NEWARK...MOVING SOUTHEAST 
AT 25 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  THORNDALE BY 920 PM EDT...
  DOWNINGTOWN...7 MILES NORTHEAST OF TOUGHKENAMON...8 MILES NORTHEAST
  OF AVONDALE AND 9 MILES SOUTHWEST OF LIONVILLE BY 925 PM EDT...
  KENNETT SQUARE AND 8 MILES SOUTHWEST OF EXTON BY 930 PM EDT...
  WEST CHESTER BY 935 PM EDT...
  WEST GOSHEN BY 940 PM EDT...

A TORNADO WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT WEDNESDAY EVENING
FOR CHESTER COUNTY. 

LAT...LON 4010 7579 3996 7598 3986 7600 3979 7574
      4002 7547

$$

MPD

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 5, 12:22 AM EDTFlash Flood WarningPHILehigh, Northampton4 hr
Jul 5, 12:25 AM EDTFlash Flood WarningPHILehigh, Northampton4 hr

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2007Every severe thunderstorm warning in 2007

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.