Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 1991
Severe Thunderstorm Warning 46, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 20, 1991, 11:17 AM EDT for Chester County, Pennsylvania. It was in force for 43 min.
The area
The counties it named.
The facts
- Issued
- Aug 20, 1991, 11:17 AM EDT (15:17 UTC)
- Expired
- Aug 20, 1991, 12:00 PM EDT
- In force
- 43 min
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Whole counties
County Chester County, PA
The nearest sounding before it
Atlantic City In, NJ (KACY), launched 12:00Z, 3.3 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.
- Mixed-layer CAPE
- 772 J/kg
- Mixed-layer CIN
- -39 J/kg
- Mixed-layer LCL
- 615 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 9 m²/s²
- 0-3 km storm-relative helicity
- 65 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.0
The text
As transmitted, in the capitals the NWS used until 2016.
000 TTAA00 KPHL 201516 SVRPHL PAC029-201600- BULLETIN - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WARNING NATIONAL WEATHER SERVICE PHILADELPHIA PA 1117 AM EDT TUE AUG 20 1991 THE NATIONAL WEATHER SERVICE IN PHILADELPHIA HAS ISSUED A SEVERE THUNDERSTORM WARNING EFFECTIVE UNTIL NOON EDT FOR PEOPLE IN THE FOLLOWING LOCATION... IN SOUTHEAST PENNSYLVANIA ...SOUTHERN CHESTER COUNTY AT 1110 AM EDT WEATHER RADAR INDICATED A POSSIBLE SEVERE THUNDERSTORM MOVING THROUGH SOUTHERN CHESTER COUNTY NEAR THE TOWN OF OXFORD. THE THUNDERSTORM WAS MOVING NORTHEAST AT 20 MILES AN HOUR AND WILL PASS THROUGH THE REST OF CHESTER COUNTY WITHIN THE HOUR. THIS IS A DANGEROUS STORM. IF YOU ARE IN THE WARNED AREA...PREPARE FOR STRONG DAMAGING WINDS...LARGE HAIL...VERY HEAVY RAIN AND DEADLY LIGHTNING. SHOULD THE STORM APPROACH YOU...SEEK IMMEDIATE SHELTER INDOORS...BUT DO NOT STAND NEAR WINDOWS. MOBILE HOMES ARE MOST VULNERABLE TO HIGH WINDS AND SHOULD BE A/VOIDED. DCY
What forecasters said that day
The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
In the hours before
Special weather statement, Aug 20, 5:24 AM EDT, 5 hours 53 minutes before
DEZ001-201030- SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE WILMINGTON DE 521 AM EDT TUE AUG 20 1991 ...THUNDERSTORMS RAPIDLY DEVELOPING OVER SOUTHERN DELAWARE AND BAY... AT 520 AM EDT WEATHER RADAR SHOWED AN AREA OF RAPIDLY DEVELOPING THUNDERSTORMS OVER THE MOUTH OF THE DELAWARE BAY SOUTHWEST INTO SOUTH CENTRAL SUSSEX COUNTY. THESE STORMS WERE MOVING RAPIDLY TO THE NORTHEAST INTO SOUTHERN NEW JERSEY AND MAY CONTAIN GUSTY WINDS...DANGEROUS LIGHTNING...AND HEAVY RAIN. BOATERS SHOULD MOVE TO SAFE HARBOR IMMEDIATELY USING CAUTION AS THESE STORMS CONTINUE TO DEVELOP. PERSONS IN SOUTH CENTRAL AND SOUTHEASTERN DELAWARE SHOULD STAY INDOORS UNTIL THE STORMS PASS DUE TO THE EXTREME DANGER OF THE CLOUD TO GROUND LIGHTNING STRIKES. STAY AWAY FROM ELECTRICAL APPLIANCES...SINKS AND DO NOT USE TELEPHONES DURING AN ELECTRICAL STORM. LIGHTNING THAT STRIKES A TELEPHONE LINE WILL BE TRANSFERRED INTO THE PHONE AND ELECTRICUTE THE USER. LOMBARDY
Special weather statement, Aug 20, 10:27 AM EDT, 50 minutes before
DEZ001-201425- SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE WILMINGTON DE 1020 AM EDT TUE AUG 20 1991 ...THUNDERSTORMS HEADING FOR NORTHERN DELAWARE... AT 1010 AM WEATHER SERVICE RADAR SHOWED A STRONG LINE OF THUNDERSTORMS STRETCHING FROM HARRISBURG PENNSYLVANIA SOUTHEASTWARD TO JUST SOUTH OF ABERDEEN MARYLAND. THESE STORMS ARE MOVING TO THE NORTHEAST AT ABOUT 30 MPH. THESE STORMS WILL BE AFFECTING THE NORTHERN AREAS OF NEW CASTLE COUNTY AFTER 1115 THIS MORNING. THESE STORMS COULD PRODUCE LOCALLY HEAVY RAIN... GUSTY WINDS...DANGEROUS LIGHTNING AND POSSIBLE HAIL. WEATHER SPOTTERS IN THE PATH OF THESE STORMS ARE REPORTING VERY HEAVY DOWN- POURS WITH ACCUMULATIONS OF MORE THAN 1 INCH AND HOUR. IF YOU SEE THREATENING WEATHER APPROACHING OR HEAR THUNDER TAKE SHELTER IMMEDIATELY INDOORS. VAUGHAN
Special weather statement, Aug 20, 10:35 AM EDT, 42 minutes before
PAZ007>012-NJZ002>004-201900- SPECIAL WEATHER STATEMENT - THUNDERSTORM AND HEAVY RAIN POTENTIAL NATIONAL WEATHER SERVICE PHILADELPHIA PA 1030 AM EDT TUE AUG 20 1991 ...LOCALLY HEAVY RAINS WITH THUNDERSTORMS MOVING INTO CHESTER COUNTY... AT 1030 THIS MORNING NATIONAL WEATHER SERVICE RADAR INDICATES HEAVY RAINS WITH THUNDERSTORMS OVER HARFORD COUNTY IN MARYLAND MOVING NORTHEAST TOWARD SOUTHERN CHESTER COUNTY. PERSONS IN SOUTHERN CHESTER COUNTY CAN EXPECT THUNDERSTORMS WITH HEAVY RAINS TO MOVE INTO THEIR AREA BY 1130 THIS MORNING. RAINFALL AMOUNTS OF 1 TO 2 INCHES IN A SHORT PERIOD OF TIME CAN BE EXPECTED WITH THE THUNDERSTORMS. EARLY THIS AFTERNOON THUNDERSTORMS ARE EXPECTED TO SPREAD THROUGHOUT THE REMAINDER OF SOUTHEASTERN PENNSYLVANIA AND THE DELAWARE VALLEY. LOCALLY HEAVY RAINS ARE EXPECTED WITH THESE THUNDERSTORMS ALSO. STAY TUNED TO NOAA WEATHER RADIO OR YOUR LOCAL RADIO OR TELEVISION STATIONS FOR THE LATEST FORECAST...AS WELL AS ANY POSSIBLE WEATHER WATCHES OR WARNINGS THAT MAY BE ISSUED LATER TODAY. GCH
Special weather statement, Aug 20, 11:03 AM EDT, 14 minutes before
PAZ011-016-201800- SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE ALLENTOWN PA 1100 AM EDT TUE AUG 20 1991 ...HEAVY SHOWERS AND THUNDERSTORMS MOVING TOWARDS EAST CENTRAL PENNSYLVANA... A LARGE AREA OF SHOWERS AND THUNDERSTORMS ARE LOCATED FROM NORTHWEST OF WILLIAMSPORT PENNSYLVANIA TO SOUTHEAST OF LANCASTER...WEST TO HAGERSTOWN MARYLAND. THIS AREA IS ABOUT 50 MILES WIDE AND CONTAINS SOME VERY HEAVY RAIN AND THUNDERSTORMS AND IS MOVING TOWARDS THE NORTHEAST AT ABOUT 30 MPH. THE LEADING EADGE OF THIS AREA SHOULD REACH THE LEHIGH VALLEY BETWEEN 1230 AND 100 PM THIS AFTERNOON. AS THE SHOWERS AND THUNDERSTORMS MOVE THROUGH THE LEHIGH VALLEY PERIODS OF HEAVY RAIN CAN BE EXPECTED. STAY TUNtED TO YOUR LOCAL RADIO AND TELEVISION STATIONS AND NOAA WEATHER RADIO FOR LATER STATEMENTS AND POSSIBLE WATCHS OR WARNINGS THAT MAY BE ISSUED LATER. GIANNETTA
Special weather statement, Aug 20, 11:16 AM EDT, 1 minute before
DEZ003-201425- SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE WILMINGTON DE 1020 AM EDT TUE AUG 20 1991 ...THUNDERSTORMS HEADING FOR NORTHERN DELAWARE... AT 1010 AM WEATHER SERVICE RADAR SHOWED A STRONG LINE OF THUNDERSTORMS STRETCHING FROM HARRISBURG PENNSYLVANIA SOUTHEASTWARD TO JUST SOUTH OF ABERDEEN MARYLAND. THESE STORMS ARE MOVING TO THE NORTHEAST AT ABOUT 30 MPH. THESE STORMS WILL BE AFFECTING THE NORTHERN AREAS OF NEW CASTLE COUNTY AFTER 1115 THIS MORNING. THESE STORMS COULD PRODUCE LOCALLY HEAVY RAIN... GUSTY WINDS...DANGEROUS LIGHTNING AND POSSIBLE HAIL. WEATHER SPOTTERS IN THE PATH OF THESE STORMS ARE REPORTING VERY HEAVY DOWN- POURS WITH ACCUMULATIONS OF MORE THAN 1u INCH AND HOUR. IF YOU SEE THREATENING WEATHER APPROACHING OR HEAR THUNDER TAKE SHELTER IMMEDIATELY INDOORS. VAUGHAN
Nearby
Severe Thunderstorm Warnings in Pennsylvania, 1991Every severe thunderstorm warning in 1991
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.