Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 245

March 11, 201217 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Mar 11, 2012, 11:17 PM CDT for 17 parishes in Louisiana. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued: Mar 11, 2012, 11:17 PM CDT (04:17 UTC)
Expired: Mar 12, 2012, 12:45 AM CDT
In force: 88 min
Issued by: the Storm Prediction Center

Counties Acadia Parish, LA, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Lafayette Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA

The radar

The Lake Charles radar (KLCH), 116 km from the middle of the area, began a volume at 04:16 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 nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 4.3 hours before the alert went out and 115 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: 1310 J/kg
Mixed-layer CIN: -14 J/kg
Mixed-layer LCL: 439 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 150 m²/s²
0-3 km storm-relative helicity: 135 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 4.3

Open this sounding in Storm Lab

The text

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

450 
ACUS11 KWNS 120418
SWOMCD
SPC MCD 120417
LAZ000-120545-

MESOSCALE DISCUSSION 0245
NWS STORM PREDICTION CENTER NORMAN OK
1117 PM CDT SUN MAR 11 2012

AREAS AFFECTED...SRN LA

CONCERNING...TORNADO WATCH 72...

VALID 120417Z - 120545Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 72 CONTINUES.

DISCRETE SUPERCELL DEVELOPMENT EAST OF LAKE CHARLES THE PAST HOUR OR
SO APPEARS TO HAVE FORMED NEAR THE CENTER OF AN INLAND
MIGRATING/DEVELOPING MESO LOW.  THE POTENTIAL LONGEVITY OF THIS
FEATURE AND THIS ACTIVITY IS UNCERTAIN...BUT CLOUD TOP COOLING
PERSISTS WITH ONGOING CONVECTIVE DEVELOPMENT NEAR COASTAL AREAS TO
THE SOUTH.  IT MAY NOT BE OUT OF THE QUESTION THAT FURTHER UPSCALE
CONVECTIVE GROWTH OCCURS ACROSS COASTAL AREAS AND ADJACENT SOUTH
CENTRAL LOUISIANA THROUGH THE 06-07Z TIME FRAME.  HOWEVER...VWP DATA
DO APPEAR TO CONFIRM CONSIDERABLE WEAKENING OF SOUTHERLY LOW-LEVEL
WIND FIELDS AND SHEAR.  SO THE LINGERING RISK FOR ISOLATED
TORNADOES/DAMAGING WIND GUSTS STILL APPEARS TO BE IN THE PROCESS OF
SLOWLY DIMINISHING.  LOCALLY HEAVY RAINFALL ASSOCIATED WITH SLOW
MOVING/PERSISTENT/TRAINING CONVECTION IN THE PRESENCE OF WEAK TO
MODERATE CAPE AND FAIRLY HIGH PRECIPITABLE WATER UP TO 1.75 INCHES
MAY BECOME AN INCREASING CONCERN.

..KERR.. 03/12/2012

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

ATTN...WFO...LIX...LCH...

LAT...LON   29689290 30289248 30749193 30849104 30369039 29269080
            28669205 28769308 29099340 29689290

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 11, 8:44 PM CDT	Mesoscale Discussion	SPC	Acadia, Avoyelles, Catahoula, Concordia, East Carroll, Evangeline and 7 more	91 min
Mar 12, 1:23 AM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, Iberia, Iberville, Livingston, Saint Charles and 5 more	2 hr
Mar 12, 8:55 AM CDT	Mesoscale Discussion	SPC	Acadia, Ascension, Assumption, Iberville, Jefferson Davis, Lafayette and 5 more	65 min
Mar 12, 4:02 PM CDT	Mesoscale Discussion	SPC	East Carroll, Madison, Richland, West Carroll	58 min

Nearby

Mesoscale Discussions in Louisiana, 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.