Alert archive / Delaware / Severe Thunderstorm Warnings in 1998

Severe Thunderstorm Warning 10, NWS Philadelphia/Mount Holly

April 1, 1998New Castle County, Delaware; Cecil County, Maryland; Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Apr 1, 1998, 9:43 PM EST for New Castle County, Delaware; Cecil County, Maryland; Chester County, Pennsylvania. It was in force for 32 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Apr 1, 1998, 9:43 PM EST (02:43 UTC)
Expired
Apr 1, 1998, 10:15 PM EST
In force
32 min
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

Counties New Castle County, DE, Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 102 km from the middle of the area, began a volume at 02:46 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

IssuedProductOfficeLasted
Apr 1, 7:15 PM ESTTornado WatchSPC5 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 2.7 hours before the alert went out and 163 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, Washington/Dulle, VA at 00:00Z on 1998-04-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1170 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 1998-04-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 104 square meters per square second.1939587897Sfc1 km3 km6 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
1170 J/kg
Mixed-layer CIN
-6 J/kg
Mixed-layer LCL
817 m above ground
0-6 km bulk shear
80 kt
0-1 km storm-relative helicity
104 m²/s²
0-3 km storm-relative helicity
192 m²/s²
Significant tornado parameter
0.6
Supercell composite
3.7

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KPHL 020243 RRA
SVRPHL
DEC003-MDC015-PAC029-020315-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
943 PM EST WED APR 1 1998

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A
SEVERE THUNDERSTORM WARNING EFFECTIVE UNTIL 1015 PM EST FOR PEOPLE
IN THE FOLLOWING LOCATIONS...

IN PENNSYLVANIA

   ...EXTREME SOUTHEASTERN CHESTER COUNTY

IN DELAWARE

   ...EXTREME NORTHERN NEW CASTLE COUNTY

IN MARYLAND

   ...NORTHEASTERN CECIL COUNTY

AT 940 PM EST... RADAR SHOWED A SEVERE THUNDERSTORM IN THE VICINITY
OF FAIRHILL MARYLAND MOVING EAST NORTHEAST AT 40 MPH.

A TORNADO WATCH REMAINS IN EFFECT FOR THE AREA UNTIL MIDNIGHT.
SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE TORNADOES WITH
LITTLE OR NO ADVANCE WARNING.

THIS IS A DANGEROUS STORM. MOVE INSIDE A STRONG BUILDING AND DO
NOT STAND NEAR WINDOWS. FOR YOUR PROTECTION MOVE TO AN INTERIOR
ROOM ON THE LOWEST FLOOR OF YOUR HOME OR BUSINESS.

DO NOT DRIVE YOUR CAR WHERE WATER COVERS THE ROADWAY. THE WATER
MAY BE DEEPER THAN YOU THINK. IF CAUGHT IN RISING FLOOD WATERS...
ABANDON YOUR CAR QUICKLY AND MOVE TO HIGHER GROUND.

FOR THE LATEST STORM INFORMATION...PLEASE TUNE TO NOA>A WEATHER
RADIO...YOUR LOCAL RADIO OR TELEVISION STATIONS...OR YOUR CABLE
TELEVISION OUTLET.

AK/DI

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 1, 9:06 PM ESTSevere Thunderstorm WarningPHICecil49 min
Apr 1, 8:10 PM ESTFlash Flood WarningPHIChester, Montgomery110 min
Apr 1, 9:25 PM ESTSevere Thunderstorm WarningPHIBucks50 min
Apr 1, 9:56 PM ESTFlash Flood WarningPHIChester, Montgomery2 hr
Apr 2, 12:30 AM ESTFlash Flood WarningPHIBucks3 hr

Nearby

Severe Thunderstorm Warnings in Delaware, 1998Severe Thunderstorm Warnings in Maryland, 1998Severe Thunderstorm Warnings in Pennsylvania, 1998Every severe thunderstorm warning in 1998

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; radar from the NEXRAD Level II archive.