Alert archive / Louisiana / Tornado Watches in 2009
Tornado Watch 166
The Storm Prediction Center issued this tornado watch at Apr 18, 2009, 1:01 PM CDT for 12 parishes in Louisiana; 9 counties in Texas. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 18, 2009, 1:01 PM CDT (18:01 UTC)
- Expired
- Apr 18, 2009, 8:00 PM CDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 21 counties
Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Grant Parish, LA, Jefferson Davis Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Winn Parish, LA, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Tyler County, TX
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
- 30%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
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 |
|---|---|---|---|---|
| Apr 18, 3:16 PM CDT | Tornado Warning | LCH | Newton | 29 min |
| Apr 18, 3:51 PM CDT | Flash Flood Warning | LCH | Jefferson | 4 hr |
| Apr 18, 4:42 PM CDT | Severe Thunderstorm Warning | LCH | Jefferson | 63 min |
| Apr 18, 6:18 PM CDT | Flash Flood Warning | LCH | Allen, Beauregard, Calcasieu, Jefferson Davis, Rapides, Vernon | 4 hr |
| Apr 18, 7:07 PM CDT | Tornado Warning | LCH | Allen, Evangeline | 23 min |
| Apr 18, 7:50 PM CDT | Flash Flood Warning | LCH | Hardin, Jefferson, Orange | 115 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, 6.0 hours before the alert went out and 104 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.
- Mixed-layer CAPE
- 778 J/kg
- Mixed-layer CIN
- -108 J/kg
- Mixed-layer LCL
- 573 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 160 m²/s²
- 0-3 km storm-relative helicity
- 499 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 8.3
The text
As transmitted, in the capitals the NWS used until 2016.
336
WWUS20 KWNS 181757
SEL6
SPC WW 181757
LAZ000-TXZ000-CWZ000-190100-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 166
NWS STORM PREDICTION CENTER NORMAN OK
100 PM CDT SAT APR 18 2009
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
WESTERN LOUISIANA
SOUTHEAST TEXAS
COASTAL WATERS
EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 100 PM UNTIL
800 PM CDT.
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 EAST AND WEST OF A LINE FROM 15 MILES NORTH NORTHWEST OF
NATCHITOCHES LOUISIANA TO 35 MILES SOUTHEAST OF PORT ARTHUR
TEXAS. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).
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...CONTINUE...WW 165...
DISCUSSION...AREA OF INTENSE THUNDERSTORMS OVER SOUTHEAST TX WILL
CONTINUE TO TRACK EASTWARD INTO WESTERN LA THIS AFTERNOON. SEVERAL
LOW LEVEL MESOCYCLONES HAVE BEEN NOTED WITH STORMS...AND THREAT WILL
PERSIST AS ACTIVITY MOVES THROUGH REGION OF STRONG LOW LEVEL SHEAR
AND AMPLE MOISTURE. TORNADOES AND LOCALLY DAMAGING WINDS ARE THE
MAIN THREATS.
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 500.
MEAN STORM MOTION VECTOR 24020.
...HARTSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 18, 3:38 PM CDT | Mesoscale Discussion | SPC | Allen, Beauregard, Calcasieu, Cameron, Evangeline, Grant and 5 more | 97 min |
| Apr 18, 5:46 PM CDT | Mesoscale Discussion | SPC | Allen, Beauregard, Calcasieu, Cameron, Evangeline, Grant and 5 more | 59 min |
| Apr 17, 9:33 PM CDT | Mesoscale Discussion | SPC | Childress, Collingsworth, Cottle, Foard, Gray, Hansford and 13 more | 27 min |
| Apr 17, 11:44 PM CDT | Mesoscale Discussion | SPC | Atascosa, La Salle, McMullen | 61 min |
| Apr 18, 3:22 AM CDT | Mesoscale Discussion | SPC | Atascosa, Bandera, Bastrop, Bee, Bexar, Blanco and 34 more | 113 min |
| Apr 18, 4:21 AM CDT | Severe Thunderstorm Watch | SPC | Aransas, Atascosa, Austin, Bandera, Bastrop, Bee and 43 more | 7 hr |
| Apr 18, 6:32 AM CDT | Mesoscale Discussion | SPC | Atascosa, Bandera, Bastrop, Bexar, Caldwell, Comal and 17 more | 118 min |
| Apr 18, 9:47 AM CDT | Mesoscale Discussion | SPC | Anderson, Angelina, Austin, Brazoria, Brazos, Chambers and 22 more | 28 min |
| Apr 18, 9:53 AM CDT | Tornado Watch | SPC | Anderson, Angelina, Austin, Brazoria, Brazos, Burleson and 23 more | 6 hr |
| Apr 18, 10:52 AM CDT | Mesoscale Discussion | SPC | Aransas, Atascosa, Bee, Calhoun, DeWitt, Duval and 15 more | 53 min |
| Apr 18, 11:26 AM CDT | Mesoscale Discussion | SPC | Anderson, Angelina, Austin, Brazoria, Brazos, Burleson and 29 more | 2 hr |
| Apr 18, 1:14 PM CDT | Mesoscale Discussion | SPC | Archer, Clay, Wichita | 61 min |
| Apr 18, 1:43 PM CDT | Mesoscale Discussion | SPC | Angelina, Austin, Brazoria, Chambers, Fort Bend, Galveston and 10 more | 92 min |
| Apr 18, 3:11 PM CDT | Severe Thunderstorm Watch | SPC | Archer, Clay, Collin, Cooke, Dallas, Denton and 14 more | 9 hr |
| Apr 18, 5:14 PM CDT | Mesoscale Discussion | SPC | Cooke, Denton, Grayson | 91 min |
Nearby
Tornado Watches in Louisiana, 2009Tornado Watches in Texas, 2009Every tornado watch in 2009
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.