Alert archive / Oklahoma / Flash Flood Warnings in 1990

Flash Flood Warning 8, NWS Norman, OK

April 20, 1990Seminole County, Oklahoma

NWS Norman, OK issued this flash flood warning at Apr 20, 1990, 12:38 AM CDT for Seminole County, Oklahoma. It was in force for 3 hr.

The area

The counties it named.

The facts

Issued
Apr 20, 1990, 12:38 AM CDT (05:38 UTC)
Expired
Apr 20, 1990, 3:45 AM CDT
In force
3 hr
Issued by
NWS Norman, OK
Area
Whole counties

County Seminole County, OK

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

Norman, OK (KOUN), launched 00:00Z, 5.6 hours before the alert went out and 72 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, Norman, OK at 00:00Z on 1990-04-20Temperature 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, Norman, OK at 00:00Z on 1990-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -2 square meters per square second.19395878Sfc1 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
607 m above ground
0-6 km bulk shear
22 kt
0-1 km storm-relative helicity
-2 m²/s²
0-3 km storm-relative helicity
222 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 KOKC 200539 RRA
FFWOKC
OKC087-125-133-049-123-200845-
 
BULLETIN - EBS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE OKLAHOMA CITY OK
1238 AM CDT FRI APR 20 1990
 
THE NATIONAL WEATHER SERVICE IN OKLAHOMA CITY HAS ISSUED A
FLASH FLOOD WARNING EFFECTIVE UNTIL  345 AM CDT
FOR THE FOLLOWING OKLAHOMA LOCATIONS...
 
IN CENTRAL OKLAHOMA
 
   ...SOUTHERN MCCLAIN COUNTY...POTTAWATOMIE COUNTY...SEMINOLE COUNTY
 
IN SOUTHEAST OKLAHOMA
 
   ...GARVIN COUNTY...NORTHERN PONTOTOC COUNTY
 
AT 1238 PM CDT RADAR INDICATED AN AREA OF THUNDERSTORMS WITH VERY
HEAVY RAINFALL NORTH OF A LINE EXTENDING FROM 10 MILES SOUTHWEST OF
PAULS VALLEY TO NEAR ADA TO WEWOKA MOVING TOWARD THE EAST-NORTHEAST
AT 20 MILES PER HOUR. RADAR RAINFALL ESTIMATES SUGGEST THAT RAIN IS
FALLING AT A RATE OF 1 TO 2 INCHES PER HOUR IN THIS AREA. SINCE THE
GROUND ALREADY IS SATURATED...NEARLY ALL OF THIS RAINFALL WILL RUN
OFF AND LIKELY WILL PRODUCE RAPID RISES ON SMALL STREAMS AND CREEKS.
 
BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE
THE DANGERS OF FLOODS AND FLASH FLOODS.  IF FLASH FLOODING IS
OBSERVED...ACT QUICKLY.  MOVE UP TO ESCAPE FLOOD WATERS.  DO
NOT STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

The office that day

Everything else NWS Norman, OK issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 20, 12:38 AM CDTFlash Flood WarningOUNGarvin, McClain, Pontotoc, Pottawatomie3 hr
Apr 20, 6:07 AM CDTSevere Thunderstorm WarningOUNCotton53 min
Apr 20, 6:39 AM CDTSevere Thunderstorm WarningOUNJefferson, Stephens51 min

Nearby

Flash Flood Warnings in Oklahoma, 1990Every flash flood warning in 1990

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.