Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 315

March 21, 201216 parishes in Louisiana; Wilkinson County, Mississippi

The Storm Prediction Center issued this mesoscale discussion at Mar 21, 2012, 7:48 AM CDT for 16 parishes in Louisiana; Wilkinson County, Mississippi. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued
Mar 21, 2012, 7:48 AM CDT (12:48 UTC)
Expired
Mar 21, 2012, 9:15 AM CDT
In force
87 min
Issued by
the Storm Prediction Center

Counties Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Wilkinson County, MS

The watches that followed

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

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 0.8 hours before the alert went out and 141 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, Slidell Radar S, LA at 12:00Z on 2012-03-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 983 joules per kilogram.LCLEL10008507005003002001001 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, Slidell Radar S, LA at 12:00Z on 2012-03-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 363 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
983 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
519 m above ground
0-6 km bulk shear
46 kt
0-1 km storm-relative helicity
363 m²/s²
0-3 km storm-relative helicity
421 m²/s²
Significant tornado parameter
1.7
Supercell composite
10.7

Open this sounding in Storm Lab

The text

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

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Mar 20, 8:02 PM CDTTornado WatchSPCBeauregard, Calcasieu, Cameron, Vernon4 hr
Mar 20, 10:23 PM CDTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Jefferson Davis, Natchitoches, Vernon67 min
Mar 20, 10:59 PM CDTTornado WatchSPCAcadia, Allen, Beauregard, Bienville, Calcasieu, Caldwell and 17 more7 hr
Mar 21, 2:17 AM CDTMesoscale DiscussionSPCAcadia, Avoyelles, Caldwell, Catahoula, Concordia, Evangeline and 17 more118 min
Mar 21, 4:38 AM CDTMesoscale DiscussionSPCAscension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 19 more97 min
Mar 21, 5:04 AM CDTTornado WatchSPCAcadia, Ascension, Assumption, Avoyelles, Caldwell, Catahoula and 33 more7 hr
Mar 21, 9:25 AM CDTMesoscale DiscussionSPCAscension, Concordia, East Baton Rouge, East Carroll, East Feliciana, Franklin and 17 more95 min
Mar 21, 10:07 AM CDTTornado WatchSPCAscension, East Carroll, East Feliciana, Franklin, Jefferson, Lafourche and 17 more8 hr
Mar 21, 12:19 PM CDTMesoscale DiscussionSPCJefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Tammany and 1 more86 min
Mar 21, 3:47 PM CDTMesoscale DiscussionSPCSaint Bernard88 min
Mar 21, 5:40 PM CDTMesoscale DiscussionSPCOrleans, Plaquemines, Saint Bernard35 min
Mar 21, 6:02 PM CDTTornado WatchSPCPlaquemines, Saint Bernard9 hr

Nearby

Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Mississippi, 2012Every 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.