Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 1991

Severe Thunderstorm Warning 4, NWS Philadelphia/Mount Holly

May 6, 1991Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at May 6, 1991, 6:06 PM EDT for Montgomery County, Pennsylvania. It was in force for 54 min.

The area

The counties it named.

The facts

Issued
May 6, 1991, 6:06 PM EDT (22:06 UTC)
Expired
May 6, 1991, 7:00 PM EDT
In force
54 min
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

County Montgomery County, PA

The nearest sounding before it

Atlantic City In, NJ (KACY), launched 12:00Z, 10.1 hours before the alert went out and 112 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 1991-05-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 1991-05-06The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 224 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
574 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
224 m²/s²
0-3 km storm-relative helicity
288 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 062209
SVRPHL
PAC091-062300-
 
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE PHILADELPHIA PA
606 PM EDT MON MAY 6 1991
 
THE NATIONAL WEATHER SERVICE IN PHILADELPHIA HAS ISSUED A
SEVERE THUNDERSTORM WARNING EFFECTIVE UNTIL  700 PM EDT
FOR PEOPLE IN THE FOLLOWING LOCATION...
 
IN SOUTHEAST PENNSYLVANIA
 
   ...MONTGOMERY COUNTY
 
AT 6 PM EDT WEATHER SERVICE RADAR SHOWED A LINE OF THUNDERSTORMS
MOVING INTO WESTERN MONTGOMERY COUNTY. STRONG GUSTY WINDS AND HAIL
ARE POSSIBLE AS THESE STRONG THUNDERSTORMS MOVE EAST THROUGH THE
COUNTY AT AROUND 45 MPH.
 
THESE THUNDERSTORMS HAVE ALREADY PRODUCED WIND GUSTS TO OVER 60
MPH AS THEY MOVED THROUGH LANCASTER COUNTTY.
 
 
 
A TORNADO/SEVERE THUNDERSTORM WATCH CONTINUES FOR SOUTHEASTERN
PENNSYLVANIA AND SOUTHERN NEW JERSEY UNTIL 1000 PM EDT.  REMEMBER
SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE TORNADOES WITH
LITTLE OR NO ADVANCED WARNING.

The office that day

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

IssuedProductOfficeCountiesLasted
May 6, 5:43 PM EDTSevere Thunderstorm WarningPHIChester32 min
May 6, 6:48 PM EDTSevere Thunderstorm WarningPHIPhiladelphia27 min

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.