Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 125

February 18, 201222 parishes in Louisiana; Hancock County, Harrison County, Pearl River County, Mississippi

The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2012, 9:31 AM CST for 22 parishes in Louisiana; Hancock County, Harrison County, Pearl River County, Mississippi. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued
Feb 18, 2012, 9:31 AM CST (15:31 UTC)
Expired
Feb 18, 2012, 10:30 AM CST
In force
59 min
Issued by
the Storm Prediction Center
All 25 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, Hancock County, MS, Harrison County, MS, Pearl River 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, 3.5 hours before the alert went out and 111 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 2012-02-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCLLFCEL10008507005003002001001 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 2012-02-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 160 square meters per square second.1939587897117Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
449 m above ground
0-6 km bulk shear
57 kt
0-1 km storm-relative helicity
160 m²/s²
0-3 km storm-relative helicity
177 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

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
Feb 18, 4:35 AM CSTMesoscale DiscussionSPCCalcasieu, Cameron, Jefferson Davis, Vermilion55 min
Feb 18, 4:46 AM CSTSevere Thunderstorm WatchSPCAcadia, Calcasieu, Cameron, Jefferson Davis, Vermilion5 hr
Feb 18, 8:29 AM CSTMesoscale DiscussionSPCAcadia, Assumption, Cameron, Iberia, Iberville, Jefferson Davis and 4 more31 min
Feb 18, 9:55 AM CSTTornado WatchSPCAscension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 15 more7 hr
Feb 18, 11:21 AM CSTMesoscale DiscussionSPCAscension, Assumption, Jefferson, Lafourche, Livingston, Orleans and 10 more54 min
Feb 18, 1:03 PM CSTMesoscale DiscussionSPCOrleans, Saint Bernard, Saint Charles57 min
Feb 18, 2:21 PM CSTMesoscale DiscussionSPCJefferson, Lafourche, Plaquemines, Saint Bernard, St. Mary, Terrebonne24 min
Feb 18, 3:41 PM CSTMesoscale DiscussionSPCJefferson, Plaquemines, Saint Bernard64 min
Feb 18, 4:29 PM CSTMesoscale DiscussionSPCJefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 1 more31 min
Feb 18, 4:48 PM CSTTornado WatchSPCLafourche, Plaquemines, Terrebonne4 hr
Feb 18, 11:49 AM CSTTornado WatchSPCGeorge, Stone5 hr
Feb 18, 2:02 PM CSTMesoscale DiscussionSPCGeorge, Harrison, Jackson58 min

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.