Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 1658
The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2021, 4:31 AM CDT for 10 counties in Alabama; 4 counties in Georgia. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Aug 31, 2021, 4:31 AM CDT (09:31 UTC)
- Expired
- Aug 31, 2021, 6:00 AM CDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Bullock County, AL, Chambers County, AL, Cleburne County, AL, Crenshaw County, AL, Lee County, AL, Macon County, AL, Montgomery County, AL, Pike County, AL, Randolph County, AL, Tallapoosa County, AL, Carroll County, GA, Haralson County, GA, Heard County, GA, Troup County, GA
The radar
The Maxwell AFB radar (KMXX), 21 km from the middle of the area, began a volume at 09:31 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 00:00Z, 9.5 hours before the alert went out and 117 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
- 182 J/kg
- Mixed-layer CIN
- -12 J/kg
- Mixed-layer LCL
- 524 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 268 m²/s²
- 0-3 km storm-relative helicity
- 284 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 1.3
The text
As transmitted.
212
ACUS11 KWNS 310931
SWOMCD
SPC MCD 310931
GAZ000-ALZ000-311100-
Mesoscale Discussion 1658
NWS Storm Prediction Center Norman OK
0431 AM CDT Tue Aug 31 2021
Areas affected...East central/southeast AL and west central GA
Concerning...Severe potential...Watch unlikely
Valid 310931Z - 311100Z
Probability of Watch Issuance...20 percent
SUMMARY...A low-end threat for a brief/weak tornado or two will
persist this morning, but a watch is not anticipated in the short
term.
DISCUSSION...The primary confluence band, to the east of the remnant
center of tropical cyclone Ida, extends from south central into east
central AL. A narrow corridor of 73-74 F surface dewpoints extends
along this confluence zone, where buoyancy is relatively larger and
coincident with the belt of stronger low-level shear/SRH. Buoyancy
is marginal for a supercell/tornado threat, but there is enough CAPE
to support updrafts producing lightning, so an isolated/weak tornado
will still be possible with the more persistent supercell structures
in the confluence band. Given that this is still well before the
diurnal heating cycle, the prospects for much ramp up in the tornado
threat appear limited. Thus, a watch is not anticipated in the next
couple of hours.
..Thompson.. 08/31/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FFC...TAE...BMX...MOB...
LAT...LON 32988590 33878565 33968519 33808483 33368485 32688510
32078556 31468598 31338639 31458662 32388612 32988590SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 31, 7:44 AM CDT | Mesoscale Discussion | SPC | Henry | 2 hr |
| Aug 31, 3:49 PM CDT | Mesoscale Discussion | SPC | Geneva, Henry, Houston, Russell | 116 min |
| Aug 31, 6:44 PM CDT | Mesoscale Discussion | SPC | Dale, Geneva, Henry, Houston | 91 min |
| Aug 31, 1:03 PM CDT | Mesoscale Discussion | SPC | Banks, Barrow, Butts, Carroll, Cherokee, Clarke and 47 more | 117 min |
Nearby
Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Georgia, 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.