Alert archive / Louisiana / Severe Thunderstorm Watches in 2006

Severe Thunderstorm Watch 621

July 19, 200624 parishes in Louisiana; 22 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at Jul 19, 2006, 4:56 PM CDT for 24 parishes in Louisiana; 22 counties in Texas. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Jul 19, 2006, 4:56 PM CDT (21:56 UTC)
Expired
Jul 20, 2006, 12:00 AM CDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.5 in
Strongest gust expected
60 kt
All 46 counties

Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, Winn Parish, LA, Angelina County, TX, Camp County, TX, Cass County, TX, Cherokee County, TX, Franklin County, TX, Gregg County, TX, Harrison County, TX, Jasper County, TX, Marion County, TX, Morris County, TX, Nacogdoches County, TX, Newton County, TX, Panola County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Smith County, TX, Titus County, TX, Tyler County, TX, Upshur County, TX, Wood County, TX

The radar

The Shreveport radar (KSHV), 86 km from the middle of the area, began a volume at 21:58 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.

What SPC expected

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

Two or more tornadoes
5%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
70%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
10%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
80%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Jul 19, 5:26 PM CDTSevere Thunderstorm WarningSHVCaldwell34 min
Jul 19, 5:39 PM CDTSevere Thunderstorm WarningSHVGrant, Winn36 min
Jul 19, 5:59 PM CDTSevere Thunderstorm WarningLCHRapides61 min
Jul 19, 6:08 PM CDTSevere Thunderstorm WarningSHVCaldwell, Ouachita37 min
Jul 19, 6:15 PM CDTSevere Thunderstorm WarningSHVBienville, Grant, Jackson, Natchitoches, Winn30 min
Jul 19, 6:48 PM CDTSevere Thunderstorm WarningSHVBienville, Grant, Jackson, Natchitoches, Winn42 min
Jul 19, 7:00 PM CDTSevere Thunderstorm WarningLCHRapides, Vernon60 min
Jul 19, 7:27 PM CDTSevere Thunderstorm WarningSHVBienville, Bossier, Natchitoches, Red River33 min
Jul 19, 7:30 PM CDTSevere Thunderstorm WarningSHVClaiborne45 min
Jul 19, 7:59 PM CDTSevere Thunderstorm WarningSHVBossier, Webster46 min
Jul 19, 8:01 PM CDTSevere Thunderstorm WarningSHVDe Soto, Red River, Sabine59 min
Jul 19, 8:13 PM CDTSevere Thunderstorm WarningSHVSabine, Shelby77 min
Jul 19, 8:32 PM CDTSevere Thunderstorm WarningSHVSan Augustine73 min
Jul 19, 8:47 PM CDTSevere Thunderstorm WarningSHVBossier, Caddo43 min
Jul 19, 9:13 PM CDTSevere Thunderstorm WarningSHVBienville, De Soto, Red River32 min
Jul 19, 9:19 PM CDTSevere Thunderstorm WarningSHVNacogdoches51 min
Jul 19, 9:28 PM CDTSevere Thunderstorm WarningSHVCaddo47 min
Jul 19, 9:45 PM CDTSevere Thunderstorm WarningSHVAngelina52 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

Shreveport, LA (KSHV), launched 12:00Z, 9.9 hours before the alert went out and 82 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, Shreveport, LA at 12:00Z on 2006-07-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3200 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, Shreveport, LA at 12:00Z on 2006-07-19The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -54 square meters per square second.193958Sfc1 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
3200 J/kg
Mixed-layer CIN
-68 J/kg
Mixed-layer LCL
1062 m above ground
0-6 km bulk shear
34 kt
0-1 km storm-relative helicity
-54 m²/s²
0-3 km storm-relative helicity
-17 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.3

Open this sounding in Storm Lab

The text

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

000 
WWUS20 KWNS 192151
SEL1  
SPC WW 192151
LAZ000-TXZ000-200500-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 621
NWS STORM PREDICTION CENTER NORMAN OK
450 PM CDT WED JUL 19 2006

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

       WESTERN AND CENTRAL LOUISIANA
       NORTHEAST TEXAS

EFFECTIVE THIS WEDNESDAY AFTERNOON FROM 450 PM UNTIL MIDNIGHT CDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES EAST
NORTHEAST OF ALEXANDRIA LOUISIANA TO 50 MILES SOUTHWEST OF
LONGVIEW TEXAS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...CONTINUE...WW 617...WW 618...WW
619...WW 620...

DISCUSSION...TSTM CLUSTER IN NE LA EXPECTED TO PROPAGATE MAINLY WSW
ALONG LOW LEVEL INSTABILITY GRADIENT THROUGH MID EVENING. 
UNIDIRECTIONAL MID/UPR LEVEL NELY FLOW WILL ENHANCE POTENTIAL FOR
SMALL SCALE BOWING SEGMENTS WITH HIGH WIND.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 07015.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 19, 1:24 PM CDTMesoscale DiscussionSPCAvoyelles, Caldwell, Catahoula, Concordia, East Carroll, East Feliciana and 18 more2 hr
Jul 19, 1:58 PM CDTSevere Thunderstorm WatchSPCCatahoula, Concordia, East Carroll, Franklin, Madison, Morehouse and 3 more6 hr
Jul 19, 3:41 PM CDTMesoscale DiscussionSPCAvoyelles, Bienville, Caldwell, Catahoula, Claiborne, Concordia and 22 more2 hr
Jul 19, 6:49 PM CDTMesoscale DiscussionSPCAvoyelles, Bienville, Bossier, Caddo, Caldwell, Catahoula and 16 more86 min

Nearby

Severe Thunderstorm Watches in Louisiana, 2006Severe Thunderstorm Watches in Texas, 2006Every severe thunderstorm watch in 2006

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.