Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 994

May 31, 201213 parishes in Louisiana; 11 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at May 31, 2012, 9:47 AM CDT for 13 parishes in Louisiana; 11 counties in Texas. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued: May 31, 2012, 9:47 AM CDT (14:47 UTC)
Expired: May 31, 2012, 10:45 AM CDT
In force: 58 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 24 counties

Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Chambers County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Montgomery County, TX, Newton County, TX, Orange County, TX, San Jacinto County, TX, Tyler County, TX

The radar

The Lake Charles radar (KLCH), 46 km from the middle of the area, began a volume at 14:46 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.

The watches that followed

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

Severe Thunderstorm Watch 327May 31, 10:40 AM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 2.8 hours before the alert went out and 47 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: 2548 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 650 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 49 m²/s²
0-3 km storm-relative helicity: 36 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.6

Open this sounding in Storm Lab

The text

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

341 
ACUS11 KWNS 311448
SWOMCD
SPC MCD 311447
LAZ000-TXZ000-311545-

MESOSCALE DISCUSSION 0994
NWS STORM PREDICTION CENTER NORMAN OK
0947 AM CDT THU MAY 31 2012

AREAS AFFECTED...SE TX...SW LA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 311447Z - 311545Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...AN ISOLATED SEVERE THREAT WILL LIKELY CONTINUE ACROSS SE
TX AND SW LA THROUGH EARLY AFTERNOON. STRONG GUSTY WINDS AND HAIL
WILL BE PRIMARY THREATS WITH THE ACTIVITY. THE AREA WILL CONTINUE TO
BE MONITORED FOR THE POSSIBILITY FOR WW ISSUANCE.

DISCUSSION...A LINE OF THUNDERSTORMS ACROSS EAST TX IS LOCATED JUST
AHEAD OF A SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY. THE
SHORTWAVE TROUGH WILL SUPPORT THE LINE FOR SEVERAL HOURS WITH THE
LINE MOVING SEWD INTO MODERATE INSTABILITY CURRENTLY IN PLACE ACROSS
SE TX AND SW LA. MESOANALYSIS ESTIMATES THAT MLCAPE IS IN THE 1500
TO 2500 J/KG RANGE WHICH WILL HELP SUSTAIN THE CONVECTION. IN
ADDITION...AN AXIS OF STRONG MID-LEVEL FLOW IS LOCATED ACROSS CNTRL
AND SOUTH TX WITH 0-6 KM SHEAR VALUES ACROSS SE TX IN THE 25 TO 45
KT RANGE. THIS ALONG WITH MID-LEVEL LAPSE RATES APPROACHING 8.0 C/KM
SHOULD SUPPORT A HAIL THREAT WITH THE STRONGER CELL ELEMENTS
EMBEDDED IN THE LINE. AS LOW-LEVEL LAPSE RATES STEEPEN AHEAD OF THE
LINE OVER THE NEXT FEW HOURS...THE WIND DAMAGE THREAT MAY INCREASE
ESPECIALLY IF THE LINE CAN DEVELOP A PERSISTENT BOWING STRUCTURE.

..BROYLES/WEISS.. 05/31/2012

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

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

LAT...LON   30079154 30569181 30809222 31279277 31309312 31269353
            31059414 30799471 30629560 30379599 29979598 29649564
            29479496 29659373 29579239 29609173 30079154

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 31, 10:41 AM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 37 more	6 hr
May 31, 1:53 PM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Livingston and 12 more	67 min
May 31, 2:53 PM CDT	Severe Thunderstorm Watch	SPC	Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 4 more	5 hr
May 30, 7:37 PM CDT	Mesoscale Discussion	SPC	Blanco, Brown, Burnet, Callahan, Coleman, Comanche and 22 more	113 min
May 30, 8:38 PM CDT	Mesoscale Discussion	SPC	Armstrong, Briscoe, Carson, Childress, Collingsworth, Cottle and 13 more	97 min
May 30, 10:15 PM CDT	Mesoscale Discussion	SPC	Blanco, Brown, Burnet, Callahan, Coleman, Comanche and 22 more	2 hr
May 31, 6:02 AM CDT	Mesoscale Discussion	SPC	Brazos, Falls, Freestone, Houston, Leon, Limestone and 5 more	88 min
May 31, 6:21 PM CDT	Mesoscale Discussion	SPC	Brewster, Jeff Davis, Pecos, Presidio, Reeves	2 hr

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; radar from the NEXRAD Level II archive.