Alert archive / Louisiana / Tornado Watches in 2007

Tornado Watch 18

February 12, 200736 parishes in Louisiana

The Storm Prediction Center issued this tornado watch at Feb 12, 2007, 10:39 PM CST for 36 parishes in Louisiana. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Feb 12, 2007, 10:39 PM CST (04:39 UTC)
Expired
Feb 13, 2007, 6:00 AM CST
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt
All 36 counties

Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
40%
One or more EF2 to EF5 tornadoes
40%
Ten or more severe wind reports
30%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
5%
One or more hailstones of 2 inches or more
10%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Feb 12, 11:39 PM CSTTornado WarningLCHAllen36 min
Feb 13, 12:02 AM CSTTornado WarningLCHIberia, Lafayette, Saint Martin, Vermilion43 min
Feb 13, 12:19 AM CSTTornado WarningLCHEvangeline26 min
Feb 13, 12:39 AM CSTTornado WarningLCHVermilion36 min
Feb 13, 12:46 AM CSTSevere Thunderstorm WarningLIXSaint Helena44 min
Feb 13, 12:47 AM CSTSevere Thunderstorm WarningLCHEvangeline, Saint Landry58 min
Feb 13, 12:50 AM CSTTornado WarningLCHIberia40 min
Feb 13, 1:00 AM CSTSevere Thunderstorm WarningLCHSaint Martin30 min
Feb 13, 1:15 AM CSTTornado WarningLCHVermilion30 min
Feb 13, 1:22 AM CSTSevere Thunderstorm WarningLIXLafourche, Terrebonne38 min
Feb 13, 1:27 AM CSTSevere Thunderstorm WarningLCHAcadia63 min
Feb 13, 1:29 AM CSTTornado WarningLCHIberia, Lafayette, Saint Martin31 min
Feb 13, 1:44 AM CSTSevere Thunderstorm WarningLCHEvangeline, Saint Landry61 min
Feb 13, 1:52 AM CSTTornado WarningLCHSaint Martin38 min
Feb 13, 2:04 AM CSTSevere Thunderstorm WarningLIXLafourche, Saint Charles41 min
Feb 13, 2:28 AM CSTTornado WarningLIXJefferson, Saint Charles32 min
Feb 13, 3:00 AM CSTTornado WarningLIXJefferson, Orleans, Saint Bernard45 min
Feb 13, 3:29 AM CSTTornado WarningLCHSt. Mary31 min
Feb 13, 3:54 AM CSTTornado WarningLIXSaint Tammany36 min
Feb 13, 4:00 AM CSTSevere Thunderstorm WarningLIXEast Baton Rouge, Livingston45 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 4.7 hours before the alert went out and 141 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, Lake Charles Mun, LA at 00:00Z on 2007-02-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 276 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, Lake Charles Mun, LA at 00:00Z on 2007-02-13The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 258 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
276 J/kg
Mixed-layer CIN
-24 J/kg
Mixed-layer LCL
585 m above ground
0-6 km bulk shear
61 kt
0-1 km storm-relative helicity
258 m²/s²
0-3 km storm-relative helicity
297 m²/s²
Significant tornado parameter
0.4
Supercell composite
2.4

Open this sounding in Storm Lab

The text

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

000
WWUS20 KWNS 130442
SEL8  
SPC WW 130442
LAZ000-CWZ000-131200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 18
NWS STORM PREDICTION CENTER NORMAN OK
1040 PM CST MON FEB 12 2007

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

       CENTRAL AND SOUTHEASTERN LOUISIANA
       COASTAL WATERS

EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 1040 PM
UNTIL 600 AM CST.

TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE
MILES EITHER SIDE OF A LINE FROM 60 MILES WEST NORTHWEST OF
LAFAYETTE LOUISIANA TO 25 MILES EAST SOUTHEAST OF NEW ORLEANS
LOUISIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

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.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 17. WATCH NUMBER 17 WILL NOT BE IN EFFECT AFTER 1040
PM CST. 

DISCUSSION...THREATS OF ISOLATED TORNADOES WILL CONTINUE TO SPREAD
EWD ACROSS WW OVERNIGHT AHEAD OF STRONG MID/UPPER LEVEL TROUGH
MOVING OVER THE SRN PLAINS.  DEEP ASCENT AND STEEPENING MID LEVEL
LAPSE RATES SHOULD OVERCOME MODEST SURFACE-BASED INSTABILITY.  GIVEN
VERY STRONG LOW AND DEEP LAYER SHEAR IN PLACE...ROTATION WILL BE
COMMON WITH STRONGER CORES WITH THREATS OF LONGER-LIVED
LINES/SUPERCELLS.  ANY STORM WHICH CAN ROOT INTO MOISTENING BOUNDARY
LAYER WILL SUSTAIN A THREAT OF TORNADOES ALONG WITH DAMAGING WINDS
AND/OR HAIL.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400.
MEAN STORM MOTION VECTOR 25030.


...EVANS

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 12, 6:27 PM CSTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 10 more2 hr
Feb 12, 9:38 PM CSTMesoscale DiscussionSPCAcadia, Allen, Assumption, Avoyelles, Beauregard, Calcasieu and 16 more97 min
Feb 13, 2:26 AM CSTMesoscale DiscussionSPCAscension, Assumption, Lafourche, Livingston, Orleans, Saint Charles and 5 more64 min
Feb 13, 5:26 AM CSTMesoscale DiscussionSPCOrleans, Saint Bernard94 min

Nearby

Tornado Watches in Louisiana, 2007Every tornado watch in 2007

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.