Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 1409
The Storm Prediction Center issued this mesoscale discussion at Jul 31, 2021, 11:10 PM CDT for 4 counties in Tennessee. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 31, 2021, 11:10 PM CDT (04:10 UTC)
- Expired
- Aug 1, 2021, 1:15 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
Counties Decatur County, TN, Henderson County, TN, Lewis County, TN, Perry County, TN
The radar
The Ft Campbell radar (KHPX), 134 km from the middle of the area, began a volume at 04:10 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, 4.2 hours before the alert went out and 137 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.
058 ACUS11 KWNS 010411 SWOMCD SPC MCD 010410 TNZ000-010615- Mesoscale Discussion 1409 NWS Storm Prediction Center Norman OK 1110 PM CDT Sat Jul 31 2021 Areas affected...Western/middle TN Concerning...Severe potential...Watch possible Valid 010410Z - 010615Z Probability of Watch Issuance...60 percent SUMMARY...Damaging winds will likely accompany a bow as it tracks southeast over the next 1-2 hours. Severe thunderstorm watch is being considered. DISCUSSION...Well-organized bow has developed over western TN late this evening. This convection is now surging southeast at 45-50kt and is likely producing severe/damaging winds as it moves across Henderson into Decatur County. Downstream convection is sagging south ahead of this convection so it should be nudged toward Lewis County along the southwestern flank of the middle TN storms. There some concern an adequate cold pool has now formed such that this activity could spread toward the AL border over the next few hours. ..Darrow/Goss.. 08/01/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OHX...MEG... LAT...LON 35928853 35718722 35318727 35558853 35928853
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 31, 10:15 PM CDT | Mesoscale Discussion | SPC | Benton, Cannon, Carroll, Crockett, Decatur, DeKalb and 12 more | 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.