Alert archive / Louisiana / Tornado Watches in 2007

Tornado Watch 737

November 25, 200726 parishes in Louisiana

The Storm Prediction Center issued this tornado watch at Nov 25, 2007, 10:29 AM CST for 26 parishes in Louisiana. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: Nov 25, 2007, 10:29 AM CST (16:29 UTC)
Expired: Nov 25, 2007, 5:00 PM CST
In force: 7 hr
Issued by: the Storm Prediction Center
Largest hail expected: 0.5 in
Strongest gust expected: 60 kt

All 26 counties

Acadia Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Cameron Parish, LA, East Baton Rouge 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, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA

What SPC expected

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

Two or more tornadoes: 30%
One or more EF2 to EF5 tornadoes: 20%
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: 5%
Six or more combined severe hail and wind reports: 40%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Nov 25, 12:20 PM CST	Severe Thunderstorm Warning	LCH	Cameron	25 min
Nov 25, 1:32 PM CST	Severe Thunderstorm Warning	LIX	Jefferson, Lafourche	43 min
Nov 25, 1:33 PM CST	Severe Thunderstorm Warning	LCH	Acadia, Lafayette, Saint Landry, Saint Martin, Vermilion	42 min
Nov 25, 2:06 PM CST	Severe Thunderstorm Warning	LIX	Pointe Coupee, West Feliciana	54 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 12:00Z, 4.5 hours before the alert went out and 158 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 462 m above ground
0-6 km bulk shear: 57 kt
0-1 km storm-relative helicity: 402 m²/s²
0-3 km storm-relative helicity: 476 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

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

000
WWUS20 KWNS 251629
SEL7  
SPC WW 251629
LAZ000-CWZ000-252300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 737
NWS STORM PREDICTION CENTER NORMAN OK
1030 AM CST SUN NOV 25 2007

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

       SOUTH CENTRAL AND SOUTHEAST LOUISIANA
       COASTAL WATERS

EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 1030 AM UNTIL
500 PM CST.

TORNADOES...HAIL TO 0.5 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 50 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST NORTHWEST OF
INTRACOASTAL CITY LOUISIANA TO 40 MILES SOUTHEAST OF NEW ORLEANS
LOUISIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

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...A WARM FRONT WILL LIFT SLOWLY NWD ACROSS SRN LA THROUGH
THE AFTERNOON IN ADVANCE OF A MID LEVEL LOW OVER TX...AND A SURFACE
LOW DEVELOPING NEWD TOWARD SW LA.  DESPITE WIDESPREAD CLOUDS AND
LIMITED SURFACE HEATING...BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S
WILL CONTRIBUTE TO SBCAPE VALUES OF 500-1000 J/KG THIS AFTERNOON
ALONG AND S OF THE WARM FRONT.  VERTICAL SHEAR WILL BE MAXIMIZED
ALONG THE BOUNDARY...WHERE SUPERCELLS AND A TORNADO OR TWO WILL BE
POSSIBLE.  OTHERWISE...ISOLATED DAMAGING WINDS CAN BE EXPECTED WITH
THE MOST INTENSE STORMS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24025.


...THOMPSON

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 25, 9:36 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Iberia, Jefferson, Lafourche, Orleans and 7 more	2 hr
Nov 25, 1:07 PM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Iberville, Jefferson, Lafayette, Lafourche and 8 more	113 min
Nov 25, 3:34 PM CST	Mesoscale Discussion	SPC	Acadia, Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville and 19 more	86 min

Nearby

Tornado Watches in Louisiana, 2007 Every 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.