Alert archive / Louisiana / Flash Flood Warnings in 1998

Flash Flood Warning 43, NWS New Orleans, LA

September 18, 1998Lafourche Parish, Terrebonne Parish, Louisiana

NWS New Orleans, LA issued this flash flood warning at Sep 18, 1998, 4:33 PM CDT for Lafourche Parish, Terrebonne Parish, Louisiana. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Sep 18, 1998, 4:33 PM CDT (21:33 UTC)
Expired
Sep 18, 1998, 7:30 PM CDT
In force
3 hr
Issued by
NWS New Orleans, LA
Area
Whole counties

Counties Lafourche Parish, LA, Terrebonne Parish, LA

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 9.6 hours before the alert went out and 128 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, Slidell Radar S, LA at 12:00Z on 1998-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 422 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, Slidell Radar S, LA at 12:00Z on 1998-09-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -2 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
422 J/kg
Mixed-layer CIN
-9 J/kg
Mixed-layer LCL
606 m above ground
0-6 km bulk shear
10 kt
0-1 km storm-relative helicity
-2 m²/s²
0-3 km storm-relative helicity
14 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 KNEW 182133
FFWNEW
LAC057-109-190030-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE NEW ORLEANS LA
433 PM CDT FRI SEP 18 1998

THE NATIONAL WEATHER SERVICE IN NEW ORLEANS LA HAS ISSUED A...

* FLASH FLOOD WARNING FOR
   - NORTHERN TERREBONNE PARISH IN SOUTHEASTERN LOUISIANA
   - LAFOURCHE PARISH IN SOUTHEASTERN LOUISIANA

* UNTIL 730 PM CDT

* AT 430 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SHOWERS AND THUNDERSTORMS WITH VERY HEAVY RAINFALL FROM
LAROSE TO HOUMA. THIS LINE WAS DRIFTING VERY SLOWLY TO THE NORTH.
RADAR RAINFALL ESTIMATES INDICATED 2 TO 3 INCHES OF RAIN HAVE
FALLEN IN THE PAST HOUR.

DUE TO THE SLOW MOVEMENT OF THESE STORMS...ADDITIONAL RAINFALL
AMOUNTS OF 2 TO 4 INCHES MAY BE EXPECTED ACROSS PORTIONS OF
TERREBONNE AND LAFOURCHE PARISHES THROUGH 630 PM. FLOODING OF LOW
LYING AREAS AND FLOOD PRONE LOCATIONS ARE LIKELY AS THESE STORMS
MOVE SLOWLY ACROSS THE AREA.

DO NOT ,DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY.  THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO
CROSS SAFELY.  VEHICLES CAUGHT IN RISING WATER SHOULD BE
ABANDONED QUICKLY.  MOVE TO HIGHER GROUND.

What forecasters said that day

The local office's own words before this flash flood 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, Sep 18, 11:40 AM CDT, 4 hours 53 minutes before
LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-191730-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1140 AM CDT FRI SEP 18 1998

MOISTURE WILL CONTINUE TO INCREASE ACROSS THE LOCAL REGION UNDER
UNSTABLIZING AIR MASS. AREA COVERAGE OF SHOWERS WILL GRADUALLY
INCREASE THROUGH TONIGHT AND SATURDAY. A FEW THUNDERSTORMS ARE
EXPECTED WITH LOCALLY HEAVY DOWNPOURS THROUGH SATURDAY.
HOWEVER...SEVERE THUNDERSTORMS ARE NOT EXPECTED.
Special weather statement, Sep 18, 11:40 AM CDT, 4 hours 53 minutes before
LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-191730-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1140 AM CDT FRI SEP 18 1998

MOISTURE WILL CONTINUE TO INCREASE ACROSS THE LOCAL REGION UNDER
UNSTABLIZING AIR MASS. AREA COVERAGE OF SHOWERS WILL GRADUALLY
INCREASE THROUGH TONIGHT AND SATURDAY. A FEW THUNDERSTORMS ARE
EXPECTED WITH LOCALLY HEAVY DOWNPOURS THROUGH SATURDAY.
HOWEVER...SEVERE THUNDERSTORMS ARE NOT EXPECTED.

The office that day

Everything else NWS New Orleans, LA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 18, 1:37 PM CDTFlash Flood WarningLIXSaint Charles113 min
Sep 18, 3:40 PM CDTFlash Flood WarningLIXJefferson, Plaquemines2 hr

Nearby

Flash Flood Warnings in Louisiana, 1998Every flash flood 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.