Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 1831

August 29, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Aug 29, 2012, 5:46 AM CDT for 4 states. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Aug 29, 2012, 5:46 AM CDT (10:46 UTC)
Expired: Aug 29, 2012, 7:15 AM CDT
In force: 89 min
Issued by: the Storm Prediction Center

All 44 counties

Baldwin County, AL, Mobile County, AL, Washington County, AL, Escambia County, FL, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Amite County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS

The radar

The Mobile radar (KMOB), 125 km from the middle of the area, began a volume at 10:49 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.

Tornado Watch 594Aug 29, 6:35 AM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 10.8 hours before the alert went out and 76 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: 275 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 509 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 392 m²/s²
0-3 km storm-relative helicity: 473 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 8.0

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.

Issued	Product	Office	Counties	Lasted
Aug 29, 1:55 AM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	2 hr
Aug 29, 6:36 AM CDT	Tornado Watch	SPC	Baldwin, Mobile, Washington	9 hr
Aug 29, 11:48 AM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	117 min
Aug 29, 3:17 PM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	28 min
Aug 29, 3:53 PM CDT	Tornado Watch	SPC	Baldwin, Mobile, Washington	8 hr
Aug 29, 5:45 PM CDT	Mesoscale Discussion	SPC	Barbour, Bullock, Butler, Coffee, Covington, Crenshaw and 6 more	90 min

Nearby

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