Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 443

April 3, 201218 parishes in Louisiana; 16 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 3, 2012, 11:24 PM CDT for 18 parishes in Louisiana; 16 counties in Texas. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Apr 3, 2012, 11:24 PM CDT (04:24 UTC)
Expired: Apr 4, 2012, 1:00 AM CDT
In force: 96 min
Issued by: the Storm Prediction Center

All 34 counties

Allen Parish, LA, Avoyelles Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Grant Parish, LA, LaSalle Parish, LA, Livingston Parish, LA, Natchitoches Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, Tangipahoa Parish, LA, Vernon Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Angelina County, TX, Austin County, TX, Colorado County, TX, Jasper County, TX, Lavaca County, TX, Montgomery County, TX, Nacogdoches County, TX, Newton County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX, Waller County, TX

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 4.4 hours before the alert went out and 75 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: 3354 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 635 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 43 m²/s²
0-3 km storm-relative helicity: 66 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 3.3

Open this sounding in Storm Lab

The text

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

558 
ACUS11 KWNS 040425
SWOMCD
SPC MCD 040424
LAZ000-MSZ000-TXZ000-040600-

MESOSCALE DISCUSSION 0443
NWS STORM PREDICTION CENTER NORMAN OK
1124 PM CDT TUE APR 03 2012

AREAS AFFECTED...CNTRL LA...SERN TX

CONCERNING...SEVERE THUNDERSTORM WATCH 137...138...

VALID 040424Z - 040600Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
137...138...CONTINUES.

POTENTIAL FOR DAMAGING WINDS AND MARGINALLY SEVERE HAIL SHOULD
REMAIN RATHER LOCALIZED WITHIN AN ARCING QLCS THAT EXTENDED FROM E/W
ACROSS NRN LA AND NE/SW IN SERN TX. OBSERVED WIND GUSTS ON THE
LEADING EDGE HAVE FALLEN TO AOB 20 KT WITH SLOWLY DIMINISHING
MID-LEVEL REFLECTIVITY CORES AND CLOUD TOP WARMING NOTED.

DESPITE THE PRESENCE OF 40-50 KT EFFECTIVE SHEAR ALONG THE TX
PORTION OF THE LINE...THE DEEP-LAYER SHEAR VECTOR HAS REMAINED
ORIENTED PARALLEL TO THE CONVECTIVE OUTFLOW. THE LACK OF A LLJ IN
THE WARM SECTOR SHOULD CONTINUE TO MINIMIZE INFLOW OF A MORE RICHLY
BUOYANT GULF COAST AIR MASS AND MAINTAIN ONLY WEAK CONVERGENCE ALONG
THE OUTFLOW. WITH LITTLE APPRECIABLE REASONING FOR THE LINE TO
UNDERGO SUBSTANTIAL INTENSIFICATION...AN EXTENSION OR NEW WW
ISSUANCE BEYOND THE 06Z SCHEDULED EXPIRATION OF WW 137 APPEARS
UNLIKELY ATTM.

FARTHER EAST IN LA...THE E/W-ORIENTED PORTION OF THE QLCS CONTINUES
TO PROGRESS S/SEWD AND MAY EVENTUALLY MERGE WITH THE SLOWER-MOVING
MCS OVER SERN LA/SRN MS. THIS TYPE OF ORIENTATION AMIDST 1.5 IN PW
VALUES COULD RESULT IN EXTENSIVE TRAINING CONVECTION CAPABLE OF
PRODUCING RATHER HEAVY RAINFALL RATES /MOST LIKELY OVER CNTRL TO
SERN LA/.

..GRAMS.. 04/04/2012

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

ATTN...WFO...JAN...LIX...LCH...SHV...HGX...CRP...EWX...

LAT...LON   29289723 29619689 30699567 31459506 31769462 31709371
            31759302 32069230 32049196 31789185 31369209 30979158
            30889070 30669034 30409047 30389095 30369176 30509252
            30729341 30739400 30489500 29559584 29039697 29289723

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 3, 8:47 PM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 4 more	58 min
Apr 3, 9:48 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 23 more	8 hr
Apr 4, 2:29 AM CDT	Mesoscale Discussion	SPC	Acadia, Ascension, Assumption, Calcasieu, Cameron, Iberia and 18 more	91 min
Apr 3, 7:35 PM CDT	Severe Thunderstorm Watch	SPC	Austin, Bastrop, Brazos, Burleson, Colorado, Fayette and 13 more	7 hr
Apr 4, 12:19 PM CDT	Mesoscale Discussion	SPC	Aransas, Austin, Bee, Brazoria, Calhoun, Chambers and 25 more	86 min
Apr 4, 12:55 PM CDT	Severe Thunderstorm Watch	SPC	Aransas, Bee, Brazoria, Brooks, Calhoun, Cameron and 19 more	6 hr
Apr 4, 3:32 PM CDT	Mesoscale Discussion	SPC	Aransas, Brazoria, Calhoun, Galveston, Kleberg, Matagorda and 1 more	88 min

Nearby

Mesoscale Discussions in Louisiana, 2012 Mesoscale Discussions in Texas, 2012 Every mesoscale discussion in 2012

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.