Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 1638
The Storm Prediction Center issued this mesoscale discussion at Aug 29, 2021, 10:04 AM CDT for 4 states. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 29, 2021, 10:04 AM CDT (15:04 UTC)
- Expired
- Aug 29, 2021, 2:00 PM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 472
All 23 counties
Baldwin County, AL, Mobile County, AL, Washington County, AL, Escambia County, FL, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS
The radar
The Mobile radar (KMOB), 56 km from the middle of the area, began a volume at 15:08 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
Slidell Radar S, LA (KSIL), launched 12:00Z, 3.1 hours before the alert went out and 103 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.
921
ACUS11 KWNS 291504
SWOMCD
SPC MCD 291504
ALZ000-FLZ000-MSZ000-LAZ000-291900-
Mesoscale Discussion 1638
NWS Storm Prediction Center Norman OK
1004 AM CDT Sun Aug 29 2021
Areas affected...southern Mississippi...southwest Alabama...western
Florida Panhandle...parts of southeastern Louisiana
Concerning...Tornado Watch 472...
Valid 291504Z - 291900Z
The severe weather threat for Tornado Watch 472 continues.
SUMMARY...Tornadoes will remain possible with the stronger cells
within outer convective bands.
DISCUSSION...An initial band of storms continues to move northward
across southern MS, southern AL, and the western FL Panhandle. The
strongest cells continues to be across southern AL and into FL where
there is access to more favorable boundary-layer theta-e. Farther
northwest into MS and curling southwest across the LA state line, a
region of cooler air exists which may be reducing tornado potential
temporarily.
With time, higher theta-e is expected to shift westward across
southern MS and much of southeastern LA, along with increasing SRH.
Additional bands of convection are expected to develop into the
area, most likely emanating from the instability axis currently near
and south of the AL/FL Panhandles where more robust bands of
convection are currently situated.
..Jewell.. 08/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...JAN...LIX...
LAT...LON 30229034 30529053 31059043 31519001 31788953 31858842
31708787 31358727 30918711 30598702 30218705 30158771
30258849 30348887 30248928 30128954 30229034SPC 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, 5:37 PM CDT | Mesoscale Discussion | SPC | Baldwin, Escambia, Mobile | 83 min |
| 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 Louisiana, 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.