Alert archive / Louisiana / Mesoscale Discussions in 2003

Mesoscale Discussion 2452

October 25, 200320 parishes in Louisiana; 9 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Oct 25, 2003, 9:17 AM CDT for 20 parishes in Louisiana; 9 counties in Texas. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: Oct 25, 2003, 9:17 AM CDT (14:17 UTC)
Expired: Oct 25, 2003, 11:15 AM CDT
In force: 118 min
Issued by: the Storm Prediction Center

All 29 counties

Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Winn Parish, LA, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, San Augustine County, TX, Tyler County, TX

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 938Oct 25, 9:45 AM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 2.3 hours before the alert went out and 34 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: 1328 J/kg
Mixed-layer CIN: -11 J/kg
Mixed-layer LCL: 769 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 127 m²/s²
0-3 km storm-relative helicity: 148 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 2.6

Open this sounding in Storm Lab

The text

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

791 
ACUS11 KWNS 251417
SWOMCD
SPC MCD 251417 
LAZ000-TXZ000-251615-

MESOSCALE DISCUSSION 2452
NWS STORM PREDICTION CENTER NORMAN OK
0917 AM CDT SAT OCT 25 2003

AREAS AFFECTED...SERN TX/MUCH OF LA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 251417Z - 251615Z

...THUNDERTORMS WILL INCREASE ACROSS MOST OF LA OVER THE NEXT
SEVERAL HOURS...A FEW MAY BE SEVERE.  SEVERE THUNDERSTORM WATCH WILL
LIKELY BE ISSUED..

WELL DEFINED UPPER VORT MAX/SHORTWAVE TROUGH ALONG THE TX COAST IS
LIFTING NEWD TOWARD LA.  THIS FEATURE WILL MAINTAIN/INCREASE WARM
ADVECTION PROFILES THROUGH LOW-MID LAYERS ACROSS THE WRN GULF REGION
WHERE MARITIME TROPICAL BOUNDARY LAYER AIRMASS IS RETURNING NWD. 
ALTHOUGH DEEP LAYER SPEED SHEAR IS NOT PARTICULARLY STRONG...IT IS
MORE THAN SUFFICIENT TO SUPPORT ISOLATED SUPERCELLS...ESPECIALLY
GIVEN THE STEEP MID LEVEL LAPSE RATES...7-8C/KM IN THE 700-500MB
LAYER...AND MLCAPES ON THE ORDER OF 1500J/KG.  LARGE HAIL SEEMS
LIKELY WITH THE STRONGEST STORMS...AND TORNADOES REMAIN
POSSIBLE...ALTHOUGH ISOLATED AND MOST LIKELY NOT THE PRIMARY SEVERE
THREAT.  SEVERE THUNDERSTORM WATCH WILL LIKELY BE REQUIRED SOON.

..DARROW.. 10/25/2003

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LIX...LCH...SHV...HGX...

30109495 31679411 32059246 30979209 30369129 29569090
29029171 29109393

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 25, 9:45 AM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 7 more	5 hr
Oct 25, 12:19 PM CDT	Mesoscale Discussion	SPC	Beauregard, Calcasieu, Sabine, Vernon	56 min
Oct 25, 2:14 PM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caldwell, Catahoula, Claiborne, Concordia and 14 more	91 min
Oct 25, 7:30 AM CDT	Mesoscale Discussion	SPC	Aransas, Brazoria, Calhoun, Chambers, Fort Bend, Galveston and 3 more	90 min
Oct 25, 1:20 PM CDT	Mesoscale Discussion	SPC	Aransas, Austin, Bee, Colorado, DeWitt, Fayette and 13 more	85 min
Oct 25, 5:21 PM CDT	Mesoscale Discussion	SPC	Atascosa, Austin, Bee, Burleson, Colorado, DeWitt and 14 more	84 min

Nearby

Mesoscale Discussions in Louisiana, 2003 Mesoscale Discussions in Texas, 2003 Every mesoscale discussion in 2003

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.