Alert archive / Tennessee / Mesoscale Discussions in 2015

Mesoscale Discussion 391

April 20, 201514 counties in Alabama; 5 counties in Mississippi; 28 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2015, 12:45 AM CDT for 14 counties in Alabama; 5 counties in Mississippi; 28 counties in Tennessee. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2015, 12:45 AM CDT (05:45 UTC)
Expired: Apr 20, 2015, 2:15 AM CDT
In force: 90 min
Issued by: the Storm Prediction Center

All 47 counties

Colbert County, AL, Cullman County, AL, Fayette County, AL, Franklin County, AL, Lamar County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Morgan County, AL, Pickens County, AL, Walker County, AL, Winston County, AL, Kemper County, MS, Lowndes County, MS, Monroe County, MS, Newton County, MS, Noxubee County, MS, Bedford County, TN, Cannon County, TN, Cheatham County, TN, Coffee County, TN, Davidson County, TN, DeKalb County, TN, Dickson County, TN, Franklin County, TN, Giles County, TN, Hickman County, TN, Jackson County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Marshall County, TN, Maury County, TN, Moore County, TN, Putnam County, TN, Robertson County, TN, Rutherford County, TN, Smith County, TN, Sumner County, TN, Trousdale County, TN, Warren County, TN, Wayne County, TN, White County, TN, Williamson County, TN, Wilson County, TN

The radar

The Northeast Alabama radar (KHTX), 121 km from the middle of the area, began a volume at 05:46 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 85Apr 20, 1:10 AM CDT

The nearest sounding before it

Nashville Metro, TN (KBNA), launched 00:00Z, 5.8 hours before the alert went out and 134 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: 170 J/kg
Mixed-layer CIN: -22 J/kg
Mixed-layer LCL: 927 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 41 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

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 20, 1:09 AM CDT	Severe Thunderstorm Watch	SPC	Blount, Cherokee, Cullman, DeKalb, Etowah, Fayette and 10 more	4 hr
Apr 20, 2:36 AM CDT	Mesoscale Discussion	SPC	Blount, Cherokee, DeKalb, Etowah, Jackson, Madison and 1 more	84 min
Apr 19, 8:02 PM CDT	Tornado Watch	SPC	Adams, Alcorn, Amite, Attala, Benton, Bolivar and 57 more	5 hr
Apr 19, 10:16 PM CDT	Mesoscale Discussion	SPC	Adams, Alcorn, Amite, Attala, Benton, Bolivar and 46 more	59 min
Apr 19, 8:21 PM CDT	Mesoscale Discussion	SPC	Lake	54 min

Nearby

Mesoscale Discussions in Tennessee, 2015 Mesoscale Discussions in Alabama, 2015 Mesoscale Discussions in Mississippi, 2015 Every mesoscale discussion in 2015

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.