Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 1644
The Storm Prediction Center issued this mesoscale discussion at Aug 29, 2021, 5:37 PM CDT for Baldwin County, Escambia County, Mobile County, Alabama; Escambia County, Okaloosa County, Santa Rosa County, Florida; 5 counties in Mississippi. It was in force for 83 min.
The area
The outline as issued.
The facts
- Issued
- Aug 29, 2021, 5:37 PM CDT (22:37 UTC)
- Expired
- Aug 29, 2021, 7:00 PM CDT
- In force
- 83 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...tornado watch likely
- Chance of a watch
- 95%
Counties Baldwin County, AL, Escambia County, AL, Mobile County, AL, Escambia County, FL, Okaloosa County, FL, Santa Rosa County, FL, George County, MS, Harrison County, MS, Jackson County, MS, Perry County, MS, Stone County, MS
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 10.6 hours before the alert went out and 139 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 3256 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- -55 m²/s²
- 0-3 km storm-relative helicity
- 85 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.3
The text
As transmitted.
002
ACUS11 KWNS 292238
SWOMCD
SPC MCD 292237
FLZ000-ALZ000-MSZ000-300000-
Mesoscale Discussion 1644
NWS Storm Prediction Center Norman OK
0537 PM CDT Sun Aug 29 2021
Areas affected...southeast LA...southern MS...southwest AL...western
FL Panhandle
Concerning...Severe potential...Tornado Watch likely
Valid 292237Z - 300000Z
Probability of Watch Issuance...95 percent
SUMMARY...The greatest risk for supercell tornado will likely remain
near the I-10 corridor early this evening. The tornado risk will
gradually spread inland later tonight as Ida moves north.
DISCUSSION...Latest surface analysis (5 pm / 22 UTC) places a
maritime warm frontal zone near I-10 over southern MS east into the
western FL Panhandle. To its south, mid 70s deg F dewpoints have
been observed with lower 70s noted farther north from Hattiesburg,
MS east to Evergreen, AL. As Ida continues to move north, the
poleward influx of higher theta-e into southern MS and southern AL
will occur. Hodographs will remain enlarged and conditionally
support low-level rotation with any stronger and more persistent
updraft. It appears the overall tornado risk will be tempered until
more cellular morphology occurs in the outer convective bands.
Nonetheless, brief tornadoes may occur with short-lived amorphous
embedded cellular structure over the next few hours. Given the
overall potential for a continuation of the conditionally favorable
environment for supercells, a new tornado watch will need to be
coordinated prior to the expiration of tornado watch 472 (7 pm / 00
UTC).
..Smith/Edwards.. 08/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TAE...MOB...JAN...LIX...
LAT...LON 30278943 30878955 31208924 31178673 30418637 30048669
29838882 30278943SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 29, 5:07 AM CDT | Mesoscale Discussion | SPC | Baldwin, Mobile | 2 hr |
| Aug 29, 6:07 AM CDT | Tornado Watch | SPC | Baldwin, Escambia, Mobile, Washington | 13 hr |
| Aug 29, 10:04 AM CDT | Mesoscale Discussion | SPC | Baldwin, Mobile, Washington | 4 hr |
| Aug 29, 6:49 PM CDT | Tornado Watch | SPC | Baldwin, Clarke, Conecuh, Escambia, Mobile, Monroe and 1 more | 11 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Florida, 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.