Alert archive / Tennessee / Mesoscale Discussions in 2018

Mesoscale Discussion 1688

December 1, 201813 counties in Alabama; 22 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at Dec 1, 2018, 5:28 PM CST for 13 counties in Alabama; 22 counties in Tennessee. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued: Dec 1, 2018, 5:28 PM CST (23:28 UTC)
Expired: Dec 1, 2018, 6:30 PM CST
In force: 62 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 35 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, Walker County, AL, Winston County, AL, Bedford County, TN, Cheatham County, TN, Davidson County, TN, Decatur County, TN, Dickson County, TN, Giles County, TN, Hardin County, TN, Hickman County, TN, Houston County, TN, Humphreys County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Marshall County, TN, Maury County, TN, Montgomery County, TN, Moore County, TN, Perry County, TN, Rutherford County, TN, Wayne County, TN, Williamson County, TN, Wilson County, TN

The radar

The Columbus AFB radar (KGWX), 118 km from the middle of the area, began a volume at 23:29 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

Little Rock, AR (KBYH), launched 12:00Z, 11.5 hours before the alert went out and 218 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: 101 J/kg
Mixed-layer CIN: -93 J/kg
Mixed-layer LCL: 793 m above ground
0-6 km bulk shear: 80 kt
0-1 km storm-relative helicity: -33 m²/s²
0-3 km storm-relative helicity: 61 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.7

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 1, 4:31 AM CST	Mesoscale Discussion	SPC	Baldwin, Choctaw, Clarke, Conecuh, Escambia, Mobile and 2 more	59 min
Dec 1, 11:16 AM CST	Tornado Watch	SPC	Coffee, Covington, Dale, Escambia, Geneva, Henry and 1 more	7 hr
Dec 1, 1:35 PM CST	Mesoscale Discussion	SPC	Coffee, Covington, Dale, Geneva, Houston	85 min
Dec 1, 3:07 PM CST	Mesoscale Discussion	SPC	Autauga, Bibb, Chilton, Clay, Coosa, Dallas and 10 more	113 min
Dec 1, 3:38 PM CST	Mesoscale Discussion	SPC	Coffee, Covington, Dale, Geneva, Houston	97 min
Dec 1, 5:53 PM CST	Tornado Watch	SPC	Coffee, Covington, Dale, Geneva, Henry, Houston	9 hr
Dec 1, 3:25 AM CST	Mesoscale Discussion	SPC	Dyer, Fayette, Haywood, Lake, Lauderdale, Shelby and 1 more	2 hr

Nearby

Mesoscale Discussions in Tennessee, 2018 Mesoscale Discussions in Alabama, 2018 Every mesoscale discussion in 2018

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.