Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 2019
The Storm Prediction Center issued this mesoscale discussion at Dec 11, 2021, 6:15 AM CST for 12 counties in Alabama; 4 counties in Mississippi; 18 counties in Tennessee. It was in force for 90 min.
The area
The outline as issued.
The facts
- Issued
- Dec 11, 2021, 6:15 AM CST (12:15 UTC)
- Expired
- Dec 11, 2021, 7:45 AM CST
- In force
- 90 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 562
All 34 counties
Cullman County, AL, Fayette County, AL, Franklin County, AL, Jackson County, AL, Lamar County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Morgan County, AL, Walker County, AL, Winston County, AL, Clay County, MS, Lowndes County, MS, Monroe County, MS, Oktibbeha County, MS, Bedford County, TN, Bledsoe County, TN, Cannon County, TN, Coffee County, TN, Cumberland County, TN, DeKalb County, TN, Franklin County, TN, Giles County, TN, Grundy County, TN, Lincoln County, TN, Marion County, TN, Marshall County, TN, Moore County, TN, Putnam County, TN, Sequatchie County, TN, Van Buren County, TN, Warren County, TN, White County, TN
The radar
The Northeast Alabama radar (KHTX), 53 km from the middle of the area, began a volume at 12:16 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
Birmingham, AL (KBMX), launched 12:00Z, 0.3 hours before the alert went out and 197 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.
- Mixed-layer CAPE
- 245 J/kg
- Mixed-layer CIN
- -11 J/kg
- Mixed-layer LCL
- 703 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 325 m²/s²
- 0-3 km storm-relative helicity
- 371 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 3.8
The text
As transmitted.
359
ACUS11 KWNS 111216
SWOMCD
SPC MCD 111215
TNZ000-ALZ000-MSZ000-111345-
Mesoscale Discussion 2019
NWS Storm Prediction Center Norman OK
0615 AM CST Sat Dec 11 2021
Areas affected...far notheast MS...northern AL and parts of Middle
TN
Concerning...Tornado Watch 562...
Valid 111215Z - 111345Z
The severe weather threat for Tornado Watch 562 continues.
SUMMARY...Damaging wind gusts and a couple of tornadoes remain
possible this morning.
DISCUSSION...Convection has solidified into a mature QLCS from
eastern portions of Middle TN into northwest AL and far northeast MS
this morning. Surface dewpoints range from the mid/upper 60s across
southern portions of the MCD area to near 60 F across northern
portions of WW 562. This is contributing to around 250-750 J/kg
MLCAPE. While instability is weak, deep-layer flow remains quite
strong, supporting the organized line of convection. Low-level flow
has become more veered with time, as is evident in both surface
observations at the progression of VWP data from KHTX. In
conjunction with limited instability, this is precluding stronger
low-level rotation. Nevertheless, severe instances of weakly
rotating cells/mesovortices have been noted over the past 1-2 hours
in regional radar data. A threat for damaging wind gusts and a
couple of tornadoes will remain possible across the remainder of WW
562 the next few hours.
..Leitman.. 12/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MRX...OHX...BMX...HUN...MEG...JAN...
LAT...LON 36268508 36218489 35898479 35318512 34618615 33738723
33288834 33318881 33468899 33798895 34588788 35318703
35928616 36278545 36268508SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 11, 2:00 AM CST | Mesoscale Discussion | SPC | Colbert, Franklin, Lauderdale, Lawrence, Limestone, Madison and 2 more | 90 min |
| Dec 11, 3:15 AM CST | Mesoscale Discussion | SPC | Colbert, Franklin, Lauderdale, Marion | 90 min |
| Dec 11, 3:41 AM CST | Tornado Watch | SPC | Colbert, Cullman, DeKalb, Fayette, Franklin, Jackson and 10 more | 6 hr |
| Dec 11, 7:34 AM CST | Mesoscale Discussion | SPC | Bibb, Blount, Calhoun, Cherokee, Clay, Cleburne and 8 more | 86 min |
| Dec 11, 10:47 AM CST | Mesoscale Discussion | SPC | Autauga, Bullock, Butler, Chambers, Clarke, Clay and 15 more | 118 min |
| Dec 10, 6:21 PM CST | Tornado Watch | SPC | Alcorn, Benton, Itawamba, Lafayette, Lee, Pontotoc and 4 more | 10 hr |
| Dec 10, 9:40 PM CST | Mesoscale Discussion | SPC | Alcorn, Benton, Coahoma, DeSoto, Lafayette, Marshall and 8 more | 2 hr |
| Dec 10, 10:00 PM CST | Mesoscale Discussion | SPC | Bolivar, Carroll, Claiborne, Hinds, Holmes, Humphreys and 8 more | 90 min |
| Dec 10, 10:09 PM CST | Mesoscale Discussion | SPC | Benton, Bolivar, Calhoun, Carroll, Coahoma, DeSoto and 14 more | 96 min |
| Dec 10, 10:44 PM CST | Tornado Watch | SPC | Alcorn, Benton, Bolivar, Calhoun, Chickasaw, Coahoma and 21 more | 6 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, 11:36 PM CST | Mesoscale Discussion | SPC | Cheatham, Dickson, Henry, Houston, Montgomery, Robertson and 2 more | 54 min |
| Dec 11, 2:51 AM CST | Mesoscale Discussion | SPC | Cheatham, Davidson, Rutherford, Williamson, Wilson | 84 min |
| Dec 11, 5:32 AM CST | Mesoscale Discussion | SPC | Anderson, Campbell, Claiborne, Fentress, Morgan, Pickett and 2 more | 88 min |
Nearby
Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Mississippi, 2021Every 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.