Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 123

February 18, 20124 parishes in Louisiana; 24 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2012, 4:35 AM CST for 4 parishes in Louisiana; 24 counties in Texas. It was in force for 55 min.

The area

The outline as issued.

The facts

Issued
Feb 18, 2012, 4:35 AM CST (10:35 UTC)
Expired
Feb 18, 2012, 5:30 AM CST
In force
55 min
Issued by
the Storm Prediction Center
All 28 counties

Calcasieu Parish, LA, Cameron Parish, LA, Jefferson Davis Parish, LA, Vermilion Parish, LA, Aransas County, TX, Austin County, TX, Brazoria County, TX, Calhoun County, TX, Chambers County, TX, Colorado County, TX, Fort Bend County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jackson County, TX, Jefferson County, TX, Kleberg County, TX, Liberty County, TX, Matagorda County, TX, Montgomery County, TX, Nueces County, TX, Orange County, TX, Refugio County, TX, San Jacinto County, TX, San Patricio County, TX, Victoria County, TX, Waller County, TX, Wharton County, TX

The radar

The Houston radar (KHGX), 72 km from the middle of the area, began a volume at 10:36 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.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 10.6 hours before the alert went out and 255 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, Lake Charles Mun, LA at 00:00Z on 2012-02-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Lake Charles Mun, LA at 00:00Z on 2012-02-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 19 square meters per square second.1939587897Sfc1 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
621 m above ground
0-6 km bulk shear
49 kt
0-1 km storm-relative helicity
19 m²/s²
0-3 km storm-relative helicity
63 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, 4:46 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, 9:31 AM CSTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 16 more59 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 17, 11:15 PM CSTMesoscale DiscussionSPCAtascosa, Austin, Bandera, Bastrop, Bell, Bexar and 54 more90 min

Nearby

Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Louisiana, 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; radar from the NEXRAD Level II archive.