Alert archive / Alabama / Mesoscale Discussions in 2011

Mesoscale Discussion 612

April 27, 201118 counties in Alabama; 17 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2011, 1:56 AM CDT for 18 counties in Alabama; 17 counties in Mississippi. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2011, 1:56 AM CDT (06:56 UTC)
Expired: Apr 27, 2011, 3:00 AM CDT
In force: 64 min
Issued by: the Storm Prediction Center

All 35 counties

Bibb County, AL, Blount County, AL, Cullman County, AL, Fayette County, AL, Greene County, AL, Hale County, AL, Jefferson County, AL, Lamar County, AL, Lawrence County, AL, Madison County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Pickens County, AL, Sumter County, AL, Tuscaloosa County, AL, Walker County, AL, Winston County, AL, Clarke County, MS, Copiah County, MS, Covington County, MS, Jasper County, MS, Jefferson Davis County, MS, Kemper County, MS, Lauderdale County, MS, Lawrence County, MS, Lincoln County, MS, Lowndes County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS

The radar

The Columbus AFB radar (KGWX), 116 km from the middle of the area, began a volume at 06:58 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 225Apr 27, 2:25 AM CDT

The nearest sounding before it

Jackson, MS (KJAN), launched 00:00Z, 6.9 hours before the alert went out and 139 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: 1600 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 1229 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: 165 m²/s²
0-3 km storm-relative helicity: 229 m²/s²
Significant tornado parameter: 2.0
Supercell composite: 12.6

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 26, 7:59 PM CDT	Mesoscale Discussion	SPC	Colbert, Franklin, Lamar, Lauderdale, Lawrence, Limestone and 1 more	2 hr
Apr 26, 9:33 PM CDT	Tornado Watch PDS	SPC	Colbert, Franklin, Lauderdale	7 hr
Apr 26, 11:33 PM CDT	Mesoscale Discussion	SPC	Colbert, Franklin, Lamar, Lauderdale, Marion	117 min
Apr 27, 2:26 AM CDT	Tornado Watch	SPC	Bibb, Blount, Calhoun, Cherokee, Chilton, Clay and 29 more	6 hr
Apr 27, 8:08 AM CDT	Tornado Watch	SPC	Colbert, Cullman, DeKalb, Fayette, Franklin, Jackson and 10 more	6 hr
Apr 27, 10:45 AM CDT	Mesoscale Discussion	SPC	Greene, Lamar, Marion, Pickens, Sumter	90 min
Apr 27, 11:39 AM CDT	Mesoscale Discussion	SPC	Cullman, DeKalb, Jackson, Madison, Marshall, Morgan	66 min
Apr 27, 1:05 PM CDT	Mesoscale Discussion	SPC	Bibb, Blount, Calhoun, Cherokee, Chilton, Choctaw and 27 more	85 min
Apr 27, 1:42 PM CDT	Tornado Watch PDS	SPC	Autauga, Bibb, Blount, Butler, Calhoun, Cherokee and 41 more	8 hr
Apr 27, 2:56 PM CDT	Mesoscale Discussion	SPC	Bibb, Blount, Calhoun, Cherokee, Chilton, Choctaw and 33 more	2 hr
Apr 27, 5:01 PM CDT	Mesoscale Discussion	SPC	Autauga, Bibb, Blount, Butler, Calhoun, Cherokee and 38 more	89 min
Apr 27, 5:41 PM CDT	Mesoscale Discussion	SPC	Barbour, Bullock, Chambers, Crenshaw, Elmore, Lee and 6 more	34 min
Apr 27, 5:52 PM CDT	Tornado Watch PDS	SPC	Barbour, Bullock, Chambers, Elmore, Lee, Macon and 5 more	9 hr
Apr 27, 6:39 PM CDT	Mesoscale Discussion	SPC	Autauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 26 more	66 min
Apr 26, 9:13 PM CDT	Mesoscale Discussion	SPC	Benton, Bolivar, Coahoma, DeSoto, Marshall, Panola and 3 more	62 min
Apr 26, 9:58 PM CDT	Tornado Watch	SPC	DeSoto, Tunica	7 hr
Apr 27, 4:53 AM CDT	Severe Thunderstorm Watch	SPC	Bolivar, Sunflower, Washington	5 hr
Apr 27, 6:25 AM CDT	Mesoscale Discussion	SPC	Alcorn, Attala, Benton, Bolivar, Calhoun, Carroll and 33 more	65 min
Apr 27, 9:48 AM CDT	Mesoscale Discussion	SPC	Claiborne, Issaquena, Washington	27 min
Apr 27, 11:02 AM CDT	Tornado Watch PDS	SPC	Adams, Alcorn, Attala, Benton, Bolivar, Calhoun and 63 more	8 hr
Apr 27, 6:27 PM CDT	Mesoscale Discussion	SPC	Clarke, Clay, Copiah, Covington, Forrest, Jasper and 22 more	33 min
Apr 27, 6:42 PM CDT	Tornado Watch	SPC	Clarke, Covington, Forrest, Jasper, Jefferson Davis, Jones and 13 more	3 hr

Nearby

Mesoscale Discussions in Alabama, 2011 Mesoscale Discussions in Mississippi, 2011 Every mesoscale discussion in 2011

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.