Alert archive / Mississippi / Mesoscale Discussions in 2009

Mesoscale Discussion 467

April 13, 200914 parishes in Louisiana; 20 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 13, 2009, 1:39 PM CDT for 14 parishes in Louisiana; 20 counties in Mississippi. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: Apr 13, 2009, 1:39 PM CDT (18:39 UTC)
Expired: Apr 13, 2009, 2:45 PM CDT
In force: 66 min
Issued by: the Storm Prediction Center

All 34 counties

Ascension Parish, LA, Avoyelles Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Jefferson 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, Simpson County, MS, Smith County, MS, Walthall County, MS, Wilkinson County, MS

The watches that followed

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

Severe Thunderstorm Watch 152Apr 13, 4:20 PM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 6.7 hours before the alert went out and 132 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1276 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: -136 m²/s²
0-3 km storm-relative helicity: 57 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -1.6

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
Apr 12, 8:07 PM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, Livingston, Orleans, Saint Bernard, Saint Charles and 6 more	53 min
Apr 12, 8:30 PM CDT	Tornado Watch	SPC	Ascension, East Baton Rouge, East Feliciana, Iberville, Livingston, Saint Helena and 4 more	6 hr
Apr 12, 10:42 PM CDT	Mesoscale Discussion	SPC	Saint Tammany, Tangipahoa, Washington	93 min
Apr 13, 4:16 PM CDT	Severe Thunderstorm Watch	SPC	East Baton Rouge, East Feliciana, Livingston, Saint Helena, Saint Tammany, Tangipahoa and 1 more	4 hr
Apr 13, 6:55 PM CDT	Mesoscale Discussion	SPC	Washington	95 min
Apr 13, 1:57 AM CDT	Mesoscale Discussion	SPC	George, Jackson	63 min
Apr 13, 2:33 AM CDT	Tornado Watch	SPC	George, Greene, Hancock, Harrison, Jackson, Stone	7 hr
Apr 13, 7:27 AM CDT	Mesoscale Discussion	SPC	Jackson	2 hr
Apr 13, 12:09 PM CDT	Mesoscale Discussion	SPC	Alcorn, Itawamba, Prentiss, Tishomingo	66 min
Apr 13, 5:52 PM CDT	Mesoscale Discussion	SPC	Lowndes, Noxubee	53 min

Nearby

Mesoscale Discussions in Mississippi, 2009 Mesoscale Discussions in Louisiana, 2009 Every mesoscale discussion in 2009

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.