Alert archive / Tennessee / Mesoscale Discussions in 2015

Mesoscale Discussion 393

April 20, 20154 states

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2015, 2:36 AM CDT for 4 states. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2015, 2:36 AM CDT (07:36 UTC)
Expired: Apr 20, 2015, 4:00 AM CDT
In force: 84 min
Issued by: the Storm Prediction Center

All 56 counties

Blount County, AL, Cherokee County, AL, DeKalb County, AL, Etowah County, AL, Jackson County, AL, Madison County, AL, Marshall County, AL, Catoosa County, GA, Chattooga County, GA, Dade County, GA, Floyd County, GA, Gordon County, GA, Murray County, GA, Walker County, GA, Whitfield County, GA, Clinton County, KY, Cumberland County, KY, Laurel County, KY, McCreary County, KY, Monroe County, KY, Pulaski County, KY, Russell County, KY, Wayne County, KY, Whitley County, KY, Anderson County, TN, Bledsoe County, TN, Bradley County, TN, Campbell County, TN, Cannon County, TN, Clay County, TN, Coffee County, TN, Cumberland County, TN, DeKalb County, TN, Fentress County, TN, Franklin County, TN, Grundy County, TN, Hamilton County, TN, Jackson County, TN, Loudon County, TN, Marion County, TN, McMinn County, TN, Meigs County, TN, Moore County, TN, Morgan County, TN, Overton County, TN, Pickett County, TN, Polk County, TN, Putnam County, TN, Rhea County, TN, Roane County, TN, Scott County, TN, Sequatchie County, TN, Smith County, TN, Van Buren County, TN, Warren County, TN, White County, TN

The radar

The Northeast Alabama radar (KHTX), 92 km from the middle of the area, began a volume at 07:38 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 nearest sounding before it

Nashville Metro, TN (KBNA), launched 00:00Z, 7.6 hours before the alert went out and 111 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, 12:45 AM CDT	Mesoscale Discussion	SPC	Colbert, Cullman, Fayette, Franklin, Lamar, Lauderdale and 8 more	90 min
Apr 20, 1:09 AM CDT	Severe Thunderstorm Watch	SPC	Blount, Cherokee, Cullman, DeKalb, Etowah, Fayette and 10 more	4 hr
Apr 20, 10:04 AM CDT	Severe Thunderstorm Watch	SPC	Appling, Atkinson, Bacon, Baker, Ben Hill, Berrien and 25 more	8 hr
Apr 20, 12:03 PM CDT	Mesoscale Discussion	SPC	Banks, Clarke, Elbert, Franklin, Habersham, Hall and 7 more	57 min
Apr 20, 12:23 PM CDT	Tornado Watch	SPC	Banks, Barrow, Clarke, Clayton, Cobb, Coweta and 22 more	7 hr
Apr 20, 3:18 PM CDT	Mesoscale Discussion	SPC	Banks, Barrow, Clarke, Elbert, Franklin, Habersham and 9 more	57 min
Apr 20, 3:36 PM CDT	Tornado Watch	SPC	Lincoln	5 hr
Apr 20, 5:45 PM CDT	Mesoscale Discussion	SPC	Banks, Barrow, Clarke, DeKalb, Elbert, Forsyth and 17 more	60 min
Apr 19, 8:21 PM CDT	Mesoscale Discussion	SPC	Ballard, Caldwell, Calloway, Carlisle, Christian, Crittenden and 12 more	54 min
Apr 19, 8:02 PM CDT	Tornado Watch	SPC	Benton, Carroll, Chester, Crockett, Decatur, Dyer and 15 more	5 hr
Apr 19, 10:16 PM CDT	Mesoscale Discussion	SPC	Benton, Carroll, Chester, Crockett, Dyer, Fayette and 13 more	59 min

Nearby

Mesoscale Discussions in Tennessee, 2015 Mesoscale Discussions in Kentucky, 2015 Mesoscale Discussions in Georgia, 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.