Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 1987

Severe Thunderstorm Warning 36, NWS Philadelphia/Mount Holly

August 9, 1987Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 9, 1987, 9:21 PM EDT for Chester County, Pennsylvania. It was in force for 59 min. 3 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, 9:21 PM EDT (01:21 UTC)
Expired: Aug 9, 1987, 10:20 PM EDT
In force: 59 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

Time	Report	Where
Aug 9, 9:27 PM EDT	Thunderstorm Wind 0	Chester, PA
Aug 9, 9:48 PM EDT	Thunderstorm Wind 0	Chester, PA
Aug 9, 10:20 PM EDT	Thunderstorm Wind 0	Chester, 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 00:00Z, 1.4 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-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: 2260 J/kg
Mixed-layer CIN: -33 J/kg
Mixed-layer LCL: 839 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 124 m²/s²
0-3 km storm-relative helicity: 159 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 5.7

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KPHL 100121
SVRPHL
PAC029-100220-
 
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE PHILADELPHIA PA
921 PM EDT SUN AUG 9 1987
 
THE NATIONAL WEATHER SERVICE HAS ISSUED A SEVERE THUNDERSTORM WARNING
EFFECTIVE UNTIL 1020 PM EDT FOR THE FOLLOWING COUNTY OF
 
SOUTHEAST PENNSYLVANIA... CHESTER
                                                                         
AT 920 PM EDT NATIONAL WEATHER SERVICE RADAR INDICATED A SEVERE 
THUNDERSTORM OVER NORTHWESTERN CHESTER COUNTY IN PENNSYLVANIA. THIS 
THUNDERSTORM WAS MOVING EAST SOUTHEAST AT 35 MPH AND SHOULD MOVE ACROSS 
CHESTER COUNTY BY 1020 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 WINDS AND
SHOULD BE AVOIDED.
                                                                         
A SEVERE THUNDERSTORM WATCH CONTINUES FOR THE AREA.
 
TCB

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 9, 10:08 PM EDT	Severe Thunderstorm Warning	PHI	Delaware	37 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 1987 Every 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.