Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 1987
Severe Thunderstorm Warning 11, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 12, 1987, 3:56 PM EDT for Chester County, Delaware County, Montgomery County, Pennsylvania. It was in force for 34 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
- Jul 12, 1987, 3:56 PM EDT (19:56 UTC)
- Expired
- Jul 12, 1987, 4:30 PM EDT
- In force
- 34 min
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Whole counties
Counties Chester County, PA, Delaware County, PA, Montgomery 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 | Remark |
|---|---|---|---|
| Jul 12, 4:00 PM EDT | Hail 0.75 | Delaware, PA | |
| Jul 12, 4:15 PM EDT | Thunderstorm Wind 0 | Chester, PA | |
| Jul 12, 4:19 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 12:00Z, 7.9 hours before the alert went out and 108 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.
- Mixed-layer CAPE
- 479 J/kg
- Mixed-layer CIN
- -119 J/kg
- Mixed-layer LCL
- 1172 m above ground
- 0-6 km bulk shear
- 6 kt
- 0-1 km storm-relative helicity
- 17 m²/s²
- 0-3 km storm-relative helicity
- 27 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
000 TTAA00 KPHL 121956 SVRPHL PAC045-029-091-122030- BULLETIN - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WARNING NATIONAL WEATHER SERVICE PHILADELPHIA PA 356 PM EDT SUN JUL 12 1987 THE NATIONAL WEATHER SERVICE HAS ISSUED A SEVERE THUNDERSTORM WARNING EFFECTIVE UNTIL 430 PM EDT FOR PEOPLE IN THE FOLLOWING COUNTIES OF SOUTHEAST PENNSYLVANIA...DELAWARE...EXTREME SOUTHEAST CHESTER AND SOUTHEAST MONTGOMERY AT 352 PM EDT RADAR INDICATED SEVERE THUNDERSTORMS OVER SOUTHEAST MONTGOMERY...WEST CENTRAL DELAWARE AND EXTREME SOUTHEAST CHESTER COUNTIES IN PENNSYLVANIA. THESE STORMS WERE NEARLY STATIONARY. THESE ARE DANGEROUS STORM AND PEOPLE IN THE WARNED AREA SHOULD BE PREPARED FOR STRONG DAMAGING WINDS...LARGE HAIL...VERY HEAVY RAIN AND LIGHTNING. SHOULD THE STORM APPROACH YOU...SEEK IMMEDIATE SHELTER. MOBILE HOMES ARE MOST VULNERABLE TO HIGH WINDS AND SHOULD BE AVOIDED. DPG
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.