Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 1987

Severe Thunderstorm Warning 34, NWS Philadelphia/Mount Holly

August 9, 1987Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 9, 1987, 7:25 PM EDT for Chester County, Pennsylvania. It was in force for 65 min. 2 reports came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued
Aug 9, 1987, 7:25 PM EDT (23:25 UTC)
Expired
Aug 9, 1987, 8:30 PM EDT
In force
65 min
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

County Chester County, PA

The radar

The WSR-88D network and its archive begin in 1991, so there is no radar volume for this alert.

What was reported inside it

TimeReportWhereRemark
Aug 9, 8:01 PM EDTThunderstorm Wind 0Chester, PA
Aug 9, 8:20 PM EDTThunderstorm Wind 0Chester, PA

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in. Storm Data before 1996 records only tornadoes, thunderstorm wind and hail.

The nearest sounding before it

Atlantic City In, NJ (KACY), launched 12:00Z, 11.4 hours before the alert went out and 122 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, Atlantic City In, NJ at 12:00Z on 1987-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 658 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, Atlantic City In, NJ at 12:00Z on 1987-08-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 59 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
658 J/kg
Mixed-layer CIN
-33 J/kg
Mixed-layer LCL
691 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
59 m²/s²
0-3 km storm-relative helicity
95 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.

000 
TTAA00 KPHL 092325
SVRPHL
PAC029-100030-
 
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE PHILADELPHIA PA
725 PM EDT SUN AUG 9 1987
 
THE NATIONAL WEATHER SERVICE HAS ISSUED A SEVERE THUNDERSTORM WARNING
EFFECTIVE UNTIL 830 PM EDT FOR THE FOLLOWING COUNTY OF
 
SOUTHEAST PENNSYLVANIA... CHESTER
                                                                         
AT 725 PM EDT NATIONAL WEATHER SERVICE RADAR INDICATED A SEVERE 
THUNDERSTORM OVR THE EASTERN EDGE OF LANCASTER COUNTY. THIS 
THUNDERSTORM WAS MOVING EAST AT 30 MILES AN HOUR AND SHOULD MOVE ACROSS 
CHESTER COUNTY BY 825 PM EDT. 
 
THIS IS A DANGEROUS STORM AND PEOPLE IN THE WARNED AREA SHOULD
PREPARE FOR STRONG DAMAGING WINDS...LARGE HAIL...VERY HEAVY RAIN
AND LIGHTNING.  SHOULD THE STORM APPROACH YOU...SEEK IMMEDIATE
SHELTER.  MOBILE TRAILERS ARE MOST VULNERABLE TO HIGH WIND\S AND
SHOULD BE AVOIDED.
                                                                         
A SEVERE THUNDERSTORM WATCH CONTINUES FOR THE AREA.
 
TCB

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 1987Every severe thunderstorm warning in 1987

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive.