Alert archive / Tennessee / Mesoscale Discussions in 2004

Mesoscale Discussion 2057

August 20, 200414 counties in Alabama; 13 counties in Mississippi; 23 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2004, 12:39 PM CDT for 14 counties in Alabama; 13 counties in Mississippi; 23 counties in Tennessee. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 20, 2004, 12:39 PM CDT (17:39 UTC)
Expired: Aug 20, 2004, 2:45 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 50 counties

Colbert County, AL, Cullman County, AL, Fayette County, AL, Franklin County, AL, Jackson County, AL, Lamar County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Morgan County, AL, Walker County, AL, Winston County, AL, Alcorn County, MS, Chickasaw County, MS, Choctaw County, MS, Clay County, MS, Itawamba County, MS, Lee County, MS, Lowndes County, MS, Monroe County, MS, Oktibbeha County, MS, Pontotoc County, MS, Prentiss County, MS, Tishomingo County, MS, Webster County, MS, Bedford County, TN, Cannon County, TN, Coffee County, TN, Decatur County, TN, Franklin County, TN, Giles County, TN, Grundy County, TN, Hardin County, TN, Hickman County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Marion County, TN, Marshall County, TN, Maury County, TN, Moore County, TN, Perry County, TN, Rutherford County, TN, Sequatchie County, TN, Van Buren County, TN, Warren County, TN, Wayne County, TN, Williamson County, TN

The radar

The Columbus AFB radar (KGWX), 99 km from the middle of the area, began a volume at 17:39 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.

Severe Thunderstorm Watch 767Aug 20, 1:35 PM CDT

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 5.7 hours before the alert went out and 167 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: 591 J/kg
Mixed-layer CIN: -67 J/kg
Mixed-layer LCL: 915 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 15 m²/s²
0-3 km storm-relative helicity: 46 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.

Issued	Product	Office	Counties	Lasted
Aug 20, 1:35 PM CDT	Severe Thunderstorm Watch	SPC	Blount, Calhoun, Colbert, Cullman, DeKalb, Etowah and 16 more	5 hr
Aug 20, 3:35 PM CDT	Mesoscale Discussion	SPC	Cherokee, Cleburne	85 min
Aug 20, 3:55 PM CDT	Severe Thunderstorm Watch	SPC	Cherokee, Clay, Cleburne, Randolph	5 hr
Aug 20, 5:48 PM CDT	Mesoscale Discussion	SPC	Calhoun, Cherokee, Cleburne, DeKalb, Etowah, Randolph and 2 more	57 min

Nearby

Mesoscale Discussions in Tennessee, 2004 Mesoscale Discussions in Alabama, 2004 Mesoscale Discussions in Mississippi, 2004 Every mesoscale discussion in 2004

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.