Alert archive / Tennessee / Mesoscale Discussions in 2021

Mesoscale Discussion 2015

December 11, 20215 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at Dec 11, 2021, 2:51 AM CST for 5 counties in Tennessee. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Dec 11, 2021, 2:51 AM CST (08:51 UTC)
Expired: Dec 11, 2021, 4:15 AM CST
In force: 84 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 558

Counties Cheatham County, TN, Davidson County, TN, Rutherford County, TN, Williamson County, TN, Wilson County, TN

The radar

The Nashville radar (KOHX), 28 km from the middle of the area, began a volume at 08:53 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, 8.9 hours before the alert went out and 18 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: 182 J/kg
Mixed-layer CIN: -168 J/kg
Mixed-layer LCL: 593 m above ground
0-6 km bulk shear: 58 kt
0-1 km storm-relative helicity: 391 m²/s²
0-3 km storm-relative helicity: 370 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.5

Open this sounding in Storm Lab

The text

As transmitted.

505 
ACUS11 KWNS 110851
SWOMCD
SPC MCD 110851 
KYZ000-110945-

Mesoscale Discussion 2014
NWS Storm Prediction Center Norman OK
0251 AM CST Sat Dec 11 2021

Areas affected...portions of east-central KY

Concerning...Tornado Watch 561...

Valid 110851Z - 110945Z

The severe weather threat for Tornado Watch 561 continues.

SUMMARY...Damaging wind gusts and a tornado or two remain possible
across WW 561.

DISCUSSION...A supercell over Marion County Kentucky has shown
periods of strong rotation with a tornado debris signature noted
over the past 15-30 minutes. Rotation associated with this storm has
recently weakened as it continues northeast into eastern portions of
the Louisville CWA. This is likely due to weaker low-level
instability as surface dewpoints drop off rather quickly from the
mid 60s to upper 50s/low 60s. While the cluster of storms over
central KY may still produce strong, damaging gusts, the narrowing
warm sector downstream may begin to limit stronger tornado potential
over the next 1-2 hours.

..Leitman.. 12/11/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...JKL...LMK...

LAT...LON   37758512 37978464 38088434 38128406 38038388 37898380
            37748387 37568399 37418441 37318484 37328503 37358519
            37478526 37758512

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 10, 6:21 PM CST	Tornado Watch	SPC	Benton, Cheatham, Chester, Davidson, Decatur, Dickson and 20 more	10 hr
Dec 10, 6:22 PM CST	Mesoscale Discussion	SPC	Crockett, Dyer, Gibson, Haywood, Lake, Lauderdale and 3 more	53 min
Dec 10, 7:41 PM CST	Mesoscale Discussion	SPC	Dyer, Gibson, Henry, Lake, Obion, Weakley	64 min
Dec 10, 8:35 PM CST	Mesoscale Discussion	SPC	Montgomery	85 min
Dec 10, 9:40 PM CST	Mesoscale Discussion	SPC	Benton, Carroll, Cheatham, Chester, Crockett, Decatur and 24 more	2 hr
Dec 10, 10:09 PM CST	Mesoscale Discussion	SPC	Benton, Carroll, Chester, Crockett, Dyer, Fayette and 14 more	96 min
Dec 10, 10:44 PM CST	Tornado Watch	SPC	Benton, Carroll, Cheatham, Chester, Crockett, Davidson and 34 more	6 hr
Dec 10, 11:36 PM CST	Mesoscale Discussion	SPC	Cheatham, Dickson, Henry, Houston, Montgomery, Robertson and 2 more	54 min
Dec 11, 2:00 AM CST	Mesoscale Discussion	SPC	Bedford, Benton, Cannon, Carroll, Cheatham, Chester and 41 more	90 min
Dec 11, 3:41 AM CST	Tornado Watch	SPC	Bedford, Bledsoe, Cannon, Clay, Coffee, Cumberland and 26 more	6 hr
Dec 11, 5:32 AM CST	Mesoscale Discussion	SPC	Anderson, Campbell, Claiborne, Fentress, Morgan, Pickett and 2 more	88 min
Dec 11, 6:15 AM CST	Mesoscale Discussion	SPC	Bedford, Bledsoe, Cannon, Coffee, Cumberland, DeKalb and 12 more	90 min

Nearby

Mesoscale Discussions in Tennessee, 2021 Every mesoscale discussion in 2021

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.