Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 1408
The Storm Prediction Center issued this mesoscale discussion at Jul 31, 2021, 10:15 PM CDT for 18 counties in Tennessee. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 31, 2021, 10:15 PM CDT (03:15 UTC)
- Expired
- Aug 1, 2021, 12:15 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Benton County, TN, Cannon County, TN, Carroll County, TN, Crockett County, TN, Decatur County, TN, DeKalb County, TN, Dickson County, TN, Gibson County, TN, Henderson County, TN, Hickman County, TN, Humphreys County, TN, Lewis County, TN, Madison County, TN, Maury County, TN, Perry County, TN, Rutherford County, TN, Warren County, TN, Williamson County, TN
The radar
The Ft Campbell radar (KHPX), 109 km from the middle of the area, began a volume at 03:17 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.
The nearest sounding before it
Nashville Metro, TN (KBNA), launched 00:00Z, 3.3 hours before the alert went out and 109 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
- 1106 J/kg
- Mixed-layer CIN
- -7 J/kg
- Mixed-layer LCL
- 1447 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 91 m²/s²
- 0-3 km storm-relative helicity
- 251 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 5.3
The text
As transmitted.
183
ACUS11 KWNS 010316
SWOMCD
SPC MCD 010315
TNZ000-010515-
Mesoscale Discussion 1408
NWS Storm Prediction Center Norman OK
1015 PM CDT Sat Jul 31 2021
Areas affected...Western and Middle Tennessee
Concerning...Severe potential...Watch unlikely
Valid 010315Z - 010515Z
Probability of Watch Issuance...20 percent
SUMMARY...Gusty winds are expected with convection across western
and middle Tennessee over the next few hours.
DISCUSSION...Northwest flow appears to be deepening/strengthening a
bit as heights fall within the base of Great Lakes/OH Valley upper
trough. Over the last few hours, an elongated band of broken
convection, about 30 miles wide, has developed from northeast
AR-western and middle TN. This activity is propagating southeast at
roughly 30-35kt within a reservoir of ~2000 J/kg MLCAPE. Given the
strengthening deep-layer northwesterly flow, and the modest cold
pool that is noted with this convection, it appears these storms may
persist for several hours, possibly generating gusty winds at times.
However, a severe thunderstorm watch is not anticipated, but will
continue to monitor this region.
..Darrow/Goss.. 08/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OHX...MEG...
LAT...LON 36028946 36208791 36098579 35638551 35448709 35458910
36028946SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 31, 11:10 PM CDT | Mesoscale Discussion | SPC | Decatur, Henderson, Lewis, Perry | 2 hr |
| Jul 31, 11:29 PM CDT | Severe Thunderstorm Watch | SPC | Bedford, Bledsoe, Bradley, Cannon, Coffee, Franklin and 19 more | 3 hr |
Nearby
Mesoscale Discussions in Tennessee, 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.