Alert archive / Alabama / Mesoscale Discussions in 2021
Mesoscale Discussion 539
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 6:10 PM CDT for 7 counties in Alabama. It was in force for 65 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 6:10 PM CDT (23:10 UTC)
- Expired
- May 4, 2021, 7:15 PM CDT
- In force
- 65 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 149
Counties Autauga County, AL, Coosa County, AL, Elmore County, AL, Lowndes County, AL, Macon County, AL, Montgomery County, AL, Tallapoosa County, AL
The radar
The Maxwell AFB radar (KMXX), 51 km from the middle of the area, began a volume at 23:10 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
Birmingham, AL (KBMX), launched 12:00Z, 11.2 hours before the alert went out and 85 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
- 2158 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 569 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 145 m²/s²
- 0-3 km storm-relative helicity
- 195 m²/s²
- Significant tornado parameter
- 1.4
- Supercell composite
- 7.3
The text
As transmitted.
170
ACUS11 KWNS 042311
SWOMCD
SPC MCD 042310
ALZ000-050015-
Mesoscale Discussion 0539
NWS Storm Prediction Center Norman OK
0610 PM CDT Tue May 04 2021
Areas affected...Portions of central AL
Concerning...Tornado Watch 149...
Valid 042310Z - 050015Z
The severe weather threat for Tornado Watch 149 continues.
SUMMARY...The greatest damaging wind and isolated tornado threat
should focus across a small part of central Alabama in the short
term.
DISCUSSION...Recent radar imagery from KBMX and KMXX show enhanced
velocities associated with a small segment of the larger bowing
complex across southern/central AL. This area will likely have the
greatest potential for severe/damaging wind gusts in the next hour
or two. An outflow boundary is also evident extending southeastward
from the most intense portion of the bow across southeastern AL. Any
isolated tornado threat may focus near this outflow boundary, as
low-level flow is backed to east-northeasterly, locally enhancing
0-1 km SRH.
..Gleason.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...MOB...
LAT...LON 32188710 32598676 33108642 33148600 33098568 32708555
32158579 31998618 32018672 32188710SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 3, 7:13 PM CDT | Mesoscale Discussion | SPC | Autauga, Bullock, Chambers, Coosa, Elmore, Lee and 4 more | 62 min |
| May 4, 5:13 AM CDT | Severe Thunderstorm Watch | SPC | Jackson, Lauderdale, Limestone, Madison | 5 hr |
| May 4, 7:31 AM CDT | Mesoscale Discussion | SPC | Jackson, Lauderdale, Limestone, Madison | 89 min |
| May 4, 8:33 AM CDT | Mesoscale Discussion | SPC | Choctaw, Clarke, Dallas, Greene, Hale, Marengo and 4 more | 117 min |
| May 4, 9:03 AM CDT | Mesoscale Discussion | SPC | Blount, Calhoun, Cherokee, Clay, Cleburne, Cullman and 20 more | 117 min |
| May 4, 9:18 AM CDT | Tornado Watch | SPC | Autauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 28 more | 7 hr |
| May 4, 2:17 PM CDT | Mesoscale Discussion | SPC | Choctaw, Greene, Marengo, Sumter | 88 min |
| May 4, 3:03 PM CDT | Mesoscale Discussion | SPC | Bibb, Blount, Calhoun, Cherokee, Chilton, Clay and 19 more | 117 min |
| May 4, 3:31 PM CDT | Tornado Watch | SPC | Autauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more | 6 hr |
| May 4, 4:46 PM CDT | Mesoscale Discussion | SPC | Autauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more | 89 min |
| May 4, 5:20 PM CDT | Mesoscale Discussion | SPC | Barbour, Bullock, Chambers, Coffee, Covington, Dale and 7 more | 85 min |
| May 4, 6:26 PM CDT | Severe Thunderstorm Watch | SPC | Barbour, Bullock, Chambers, Coffee, Covington, Crenshaw and 8 more | 6 hr |
Nearby
Mesoscale Discussions in Alabama, 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.