Alert archive / Pennsylvania / Flash Flood Warnings in 1989

Flash Flood Warning 21, NWS Philadelphia/Mount Holly

July 5, 1989Chester County, Delaware County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 5, 1989, 8:38 AM EDT for Chester County, Delaware County, Pennsylvania. It was in force for 3 hr.

The area

The counties it named.

The facts

Issued
Jul 5, 1989, 8:38 AM EDT (12:38 UTC)
Expired
Jul 5, 1989, 11:45 AM EDT
In force
3 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

Counties Chester County, PA, Delaware County, PA

The radar

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

The nearest sounding before it

Atlantic City In, NJ (KACY), launched 12:00Z, 0.6 hours before the alert went out and 107 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 1989-07-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 480 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 1989-07-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 102 square meters per square second.1939Sfc1 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
480 J/kg
Mixed-layer CIN
-5 J/kg
Mixed-layer LCL
544 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
102 m²/s²
0-3 km storm-relative helicity
185 m²/s²
Significant tornado parameter
0.2
Supercell composite
1.9

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KPHL 051238 RRA
FFWPHL
PAC029-045-101-051545-
 
BULLETIN - EBS ACTIVATION REQUESTED
SMALL STREAM AND URBAN FLOOD WARNING
NATIONAL WEATHER SERVICE PHILADELPHIA PA
838 AM EDT WED JUL 5 1989
 
THE NATIONAL WEATHER SERVICE IN PHILADELPHIA HAS ISSUED A
SMALL STREAM AND URBAN FLOOD WARNING EFFECTIVE UNTIL 1145 AM EDT
FOR PEOPLE IN THE FOLLOWING COUNTIES...
 
IN SOUTHEAST PENNSYLVANIA
          ...CHESTER...DELAWARE...PHILADELPHIA
 
HEAVY RAINS FROM MARYLAND AND DELAWARE ARE MOVING NORTH AT AROUND
15 MILES AN HOUR. REPORTS OR 5 INCHES OR MORE HAVE FALLEN ACROSS
PORTIONS OF MARYLAND AND NORTHERN DELAWARE SINCE MIDNIGHT.  HEAVY
RAINS ARE FALLING OVER THE AREA...AND ARE EXPECTED TO CONTINUE FOR
MUCH OF TODAY.
 
IF YOU ARE IN THE WARNED COUNTY IN AN AREA SUBJECT TO FLOODING
MOVE TO HIGHER GROUND.  DO NOT DRIVE THROUGH FLOOD WATERS.
CLIMBING ATOP YOUR STALLED VEHICLE WILL NOT PREVENT YOU FROM
BEING SWEPT INTO DANGEROUS STREAM CONDITIONS AS WATER LEVELS RISE.
 
JWH
N

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 5, 8:38 AM EDTFlash Flood WarningPHIPhiladelphia3 hr
Jul 5, 9:02 AM EDTFlash Flood WarningPHIBucks3 hr
Jul 5, 10:41 AM EDTFlash Flood WarningPHIMontgomery4 hr
Jul 5, 11:00 AM EDTFlash Flood WarningPHIBucks5 hr
Jul 5, 11:00 AM EDTFlash Flood WarningPHIChester, Delaware, Montgomery5 hr
Jul 5, 11:00 AM EDTFlash Flood WarningPHIPhiladelphia5 hr

Nearby

Flash Flood Warnings in Pennsylvania, 1989Every flash flood warning in 1989

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.