Alert archive / Mississippi / Mesoscale Discussions in 2009

Mesoscale Discussion 460

April 12, 200918 counties in Alabama; 12 parishes in Louisiana; 27 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 12, 2009, 8:07 PM CDT for 18 counties in Alabama; 12 parishes in Louisiana; 27 counties in Mississippi. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued: Apr 12, 2009, 8:07 PM CDT (01:07 UTC)
Expired: Apr 12, 2009, 9:00 PM CDT
In force: 53 min
Issued by: the Storm Prediction Center

All 57 counties

Autauga County, AL, Bibb County, AL, Butler County, AL, Chilton County, AL, Choctaw County, AL, Clarke County, AL, Conecuh County, AL, Dallas County, AL, Greene County, AL, Hale County, AL, Lowndes County, AL, Marengo County, AL, Mobile County, AL, Monroe County, AL, Perry County, AL, Sumter County, AL, Washington County, AL, Wilcox County, AL, Ascension Parish, LA, Assumption Parish, LA, Livingston Parish, LA, Orleans 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, Washington Parish, LA, Clarke County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Newton County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 111 km from the middle of the area, began a volume at 01:09 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

Jackson, MS (KJAN), launched 00:00Z, 1.1 hours before the alert went out and 121 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: 48 J/kg
Mixed-layer CIN: -57 J/kg
Mixed-layer LCL: 571 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 448 m²/s²
0-3 km storm-relative helicity: 681 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

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, 8:30 PM CDT	Tornado Watch	SPC	Choctaw, Clarke, Greene, Hale, Marengo, Mobile and 2 more	6 hr
Apr 12, 10:42 PM CDT	Mesoscale Discussion	SPC	Autauga, Baldwin, Barbour, Bibb, Bullock, Butler and 33 more	93 min
Apr 12, 11:01 PM CDT	Tornado Watch	SPC	Autauga, Baldwin, Butler, Conecuh, Covington, Crenshaw and 8 more	4 hr
Apr 13, 1:57 AM CDT	Mesoscale Discussion	SPC	Baldwin, Barbour, Bullock, Butler, Coffee, Conecuh and 13 more	63 min
Apr 13, 2:33 AM CDT	Tornado Watch	SPC	Baldwin, Barbour, Bullock, Butler, Clarke, Coffee and 14 more	7 hr
Apr 13, 4:32 AM CDT	Mesoscale Discussion	SPC	Baldwin, Barbour, Bullock, Butler, Coffee, Conecuh and 10 more	58 min
Apr 13, 7:27 AM CDT	Mesoscale Discussion	SPC	Baldwin, Coffee, Covington, Dale, Escambia, Geneva and 3 more	2 hr
Apr 13, 9:12 AM CDT	Tornado Watch	SPC	Coffee, Covington, Dale, Escambia, Geneva, Henry and 1 more	9 hr
Apr 13, 11:15 AM CDT	Mesoscale Discussion	SPC	Baldwin, Barbour, Bullock, Butler, Clarke, Coffee and 11 more	90 min
Apr 13, 12:09 PM CDT	Mesoscale Discussion	SPC	Colbert, Franklin, Lauderdale, Lawrence, Limestone, Marion and 2 more	66 min
Apr 13, 12:58 PM CDT	Tornado Watch	SPC	Colbert, Cullman, DeKalb, Franklin, Jackson, Lauderdale and 5 more	7 hr
Apr 13, 4:16 PM CDT	Severe Thunderstorm Watch	SPC	Choctaw	4 hr
Apr 13, 5:52 PM CDT	Mesoscale Discussion	SPC	Blount, Cullman, DeKalb, Etowah, Fayette, Jackson and 10 more	53 min
Apr 13, 6:55 PM CDT	Mesoscale Discussion	SPC	Bibb, Chilton, Choctaw, Clarke, Dallas, Greene and 9 more	95 min
Apr 13, 1:39 PM CDT	Mesoscale Discussion	SPC	Ascension, Avoyelles, Concordia, East Baton Rouge, East Feliciana, Iberville and 8 more	66 min

Nearby

Mesoscale Discussions in Mississippi, 2009 Mesoscale Discussions in Alabama, 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; radar from the NEXRAD Level II archive.