Alert archive / Louisiana / Tornado Watches in 2001

Tornado Watch 846

December 13, 200112 parishes in Louisiana; 10 counties in Texas

The Storm Prediction Center issued this tornado watch at Dec 13, 2001, 12:00 PM CST for 12 parishes in Louisiana; 10 counties in Texas. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Dec 13, 2001, 12:00 PM CST (18:00 UTC)
Expired: Dec 13, 2001, 6:00 PM CST
In force: 6 hr
Issued by: the Storm Prediction Center

All 22 counties

Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Rapides Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Brazoria County, TX, Chambers County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Newton County, TX, Orange County, TX

The radar

The Lake Charles radar (KLCH), 95 km from the middle of the area, began a volume at 17:59 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.

Warnings issued inside it

6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Dec 13, 12:34 PM CST	Severe Thunderstorm Warning	LCH	Newton	56 min
Dec 13, 3:08 PM CST	Severe Thunderstorm Warning	LCH	Vernon	67 min
Dec 13, 3:13 PM CST	Flash Flood Warning	LCH	Vernon	4 hr
Dec 13, 3:30 PM CST	Severe Thunderstorm Warning	SHV	LaSalle	60 min
Dec 13, 4:26 PM CST	Severe Thunderstorm Warning	LCH	Cameron	49 min
Dec 13, 4:35 PM CST	Severe Thunderstorm Warning	LCH	Allen	55 min

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 6.0 hours before the alert went out and 96 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 47 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 514 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: -63 m²/s²
0-3 km storm-relative helicity: 45 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 
WWUS20 KWNS 131727
SEL6  
SPC WW 131719
LAZ000-TXZ000-CWZ000-140000-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 846
STORM PREDICTION CENTER NORMAN OK
1119 AM CST THU DEC 13 2001

THE STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

   SOUTHWEST LOUISIANA                          
   SOUTHEAST TEXAS                              
   AND ADJACENT COASTAL WATERS                     

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM NOON CST UNTIL
600 PM CST.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 70 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 50 MILES SOUTH SOUTHWEST OF HOUSTON TEXAS TO
45 MILES SOUTH SOUTHEAST OF ALEXANDRIA LOUISIANA.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. 
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.


DISCUSSION...AIR MASS IS DESTABILIZING OVER EXTREME SERN TX INTO
THE SWRN QUARTER OF LA AS MAIN TROUGH MOVES EWD OVER CENTRAL TX. 
WARM FRONTAL-TYPE BOUNDARY IS SLOWLY MOVING ONSHORE OVER SRN LA
WHICH WILL ENHANCE LOW LEVEL CONVERGENCE/STREAMWISE VORTICITY
ACROSS THE AREA.  SHEAR PROFILES ARE INCREASING AS WEAK SURFACE
FLOW IS BACKING IN RESPONSE TO APPROACHING SYSTEM AND INCREASING
THE THREAT FOR SUPERCELLS NEXT SEVERAL HOURS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES.  EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. 
MEAN STORM MOTION VECTOR 23035.


...MCCARTHY

295,0953 314,0920 294,0920 275,0953

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 13, 5:00 PM CST	Tornado Watch	SPC	Acadia, Allen, Avoyelles, Catahoula, Concordia, East Baton Rouge and 16 more	5 hr

Nearby

Tornado Watches in Louisiana, 2001 Tornado Watches in Texas, 2001 Every tornado watch in 2001

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.