Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 418
The Storm Prediction Center issued this mesoscale discussion at Apr 24, 2021, 3:04 AM CDT for Baldwin County, Mobile County, Washington County, Alabama; 10 parishes in Louisiana; 9 counties in Mississippi. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Apr 24, 2021, 3:04 AM CDT (08:04 UTC)
- Expired
- Apr 24, 2021, 5:00 AM CDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 104...105
All 22 counties
Baldwin County, AL, Mobile County, AL, Washington County, AL, Ascension Parish, LA, Assumption Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS
The radar
The Mobile radar (KMOB), 93 km from the middle of the area, began a volume at 08:07 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 00:00Z, 8.1 hours before the alert went out and 60 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
- 873 m above ground
- 0-6 km bulk shear
- 62 kt
- 0-1 km storm-relative helicity
- 156 m²/s²
- 0-3 km storm-relative helicity
- 263 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
244
ACUS11 KWNS 240804
SWOMCD
SPC MCD 240804
ALZ000-FLZ000-MSZ000-LAZ000-241000-
Mesoscale Discussion 0418
NWS Storm Prediction Center Norman OK
0304 AM CDT Sat Apr 24 2021
Areas affected...southeast Louisiana...southern Mississippi and
Alabama
Concerning...Tornado Watch 104...105...
Valid 240804Z - 241000Z
The severe weather threat for Tornado Watch 104, 105 continues.
SUMMARY...The threat for damaging wind gusts may be increasing,
along with a threat of a brief tornado or two. Eastern parts of WW
104 may need to be extended in time prior to expiration.
DISCUSSION...Surface analysis shows gradually increasingly theta-e
ahead of a consolidating line of storms extending from near New
Iberia LA toward Hattiesburg MS. VWPs from the area show very strong
flow just off the surface, with 55-65 kt in the lowest 2 km. Indeed,
a gust to 55 kt was recently measured at New Iberia, indicating
downward momentum transfer. Radar presentation over the past hour
shows a better organized line of storms moving into southeast LA,
thus damaging-wind potential may be increasing. Other strong cells
persist along the warm front from southern MS into southwest AL
where theta-e also continues to increase.
0-1 km SRH on the order of 300-500 m2/s2 also indicates supercell
potential, with attendant threat of brief tornadoes as storm mode
becomes primarily linear.
..Jewell.. 04/24/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...JAN...LIX...LCH...
LAT...LON 29939141 30359088 30719031 31098964 31388882 31628814
31608766 31508747 31288732 30888724 30608741 30208786
30188836 30108908 29948949 29829003 29849091 29839134
29939141SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 24, 1:00 AM CDT | Mesoscale Discussion | SPC | Baldwin, Coffee, Conecuh, Covington, Escambia, Geneva and 2 more | 3 hr |
| Apr 24, 1:00 AM CDT | Mesoscale Discussion | SPC | Baldwin, Coffee, Conecuh, Covington, Escambia, Geneva and 2 more | 3 hr |
| Apr 24, 1:23 AM CDT | Tornado Watch | SPC | Baldwin, Clarke, Conecuh, Covington, Escambia, Mobile and 2 more | 8 hr |
| Apr 24, 4:26 AM CDT | Mesoscale Discussion | SPC | Conecuh, Covington, Escambia, Monroe, Washington | 2 hr |
| Apr 24, 5:22 AM CDT | Tornado Watch | SPC | Coffee, Dale, Geneva, Henry, Houston | 9 hr |
| Apr 24, 7:29 AM CDT | Mesoscale Discussion | SPC | Coffee, Dale, Geneva, Henry, Houston | 91 min |
| Apr 24, 12:29 PM CDT | Mesoscale Discussion | SPC | Baldwin, Choctaw, Clarke, Conecuh, Escambia, Marengo and 4 more | 2 hr |
| Apr 24, 1:17 PM CDT | Severe Thunderstorm Watch | SPC | Autauga, Baldwin, Barbour, Bullock, Butler, Choctaw and 23 more | 8 hr |
| Apr 24, 1:22 PM CDT | Mesoscale Discussion | SPC | Blount, Calhoun, Cherokee, Clay, Cleburne, Colbert and 22 more | 113 min |
| Apr 24, 3:40 PM CDT | Mesoscale Discussion | SPC | Autauga, Barbour, Bullock, Butler, Clarke, Coffee and 19 more | 95 min |
| Apr 24, 4:52 PM CDT | Severe Thunderstorm Watch | SPC | Bibb, Blount, Calhoun, Chambers, Cherokee, Chilton and 15 more | 4 hr |
| Apr 24, 5:56 PM CDT | Mesoscale Discussion | SPC | Barbour, Bullock, Coffee, Dale, Henry, Houston and 1 more | 94 min |
| Apr 24, 6:13 PM CDT | Mesoscale Discussion | SPC | Calhoun, Chambers, Cherokee, Clay, Cleburne, Coosa and 6 more | 2 hr |
| Apr 23, 8:30 PM CDT | Tornado Watch | SPC | Allen, Avoyelles, Beauregard, Catahoula, Concordia, East Baton Rouge and 16 more | 8 hr |
| Apr 23, 10:29 PM CDT | Mesoscale Discussion | SPC | Allen, Avoyelles, Concordia, East Baton Rouge, East Feliciana, Evangeline and 10 more | 2 hr |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Mississippi, 2021Mesoscale 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.