Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 1918
The Storm Prediction Center issued this mesoscale discussion at Oct 27, 2021, 5:13 PM CDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 27, 2021, 5:13 PM CDT (22:13 UTC)
- Expired
- Oct 27, 2021, 7:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 542
Counties Baldwin County, AL, Mobile County, AL, Escambia County, FL, Orleans Parish, LA, Saint Bernard Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, Forrest County, MS, George County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Lamar County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS, Walthall County, MS
The radar
The Mobile radar (KMOB), 85 km from the middle of the area, began a volume at 22:14 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
Slidell Radar S, LA (KSIL), launched 12:00Z, 10.2 hours before the alert went out and 64 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
- 1792 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 186 m²/s²
- 0-3 km storm-relative helicity
- 274 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
803
ACUS11 KWNS 272214
SWOMCD
SPC MCD 272213
FLZ000-ALZ000-MSZ000-LAZ000-280015-
Mesoscale Discussion 1918
NWS Storm Prediction Center Norman OK
0513 PM CDT Wed Oct 27 2021
Areas affected...southeast Louisiana...far southern Mississippi and
Alabama
Concerning...Tornado Watch 542...
Valid 272213Z - 280015Z
The severe weather threat for Tornado Watch 542 continues.
SUMMARY...The threat for isolated tornadoes and damaging gusts
persist across the watch area, and may eventually spread east later
this evening.
DISCUSSION...A substantial line of storms continues to move east
across south-central MS and into southeast LA, with a warm front
draped from northwest to southeast across southern MS. South of this
boundary, boundary layer moisture is quite substantial with 75-77 F
dewpoints. Given this moist air mass, cells are easily forming in
the warm advection zone near and spreading north of the warm front.
At times, some of these cells have exhibited brief periods rotation.
While storm interference remains possible, effective SRH near 300
m2/s2 along the warm front conditionally favors a supercell capable
of brief tornadoes. Otherwise, damaging gusts and/or brief
circulations also remain possible within the main squall line as it
proceeds east.
Farther east toward Mobile and the western FL Panhandle, degree of
moisture return and destabilization is less certain, but will need
to be monitored through evening.
..Jewell/Grams.. 10/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...JAN...LIX...
LAT...LON 31259023 31318978 31198906 30908799 30708749 30498714
30298711 30188774 30188828 30158856 29918869 29758884
29808932 29909019 30089065 30339067 30659052 31139037
31259023SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 27, 7:36 AM CDT | Mesoscale Discussion | SPC | Acadia, Beauregard, Calcasieu, Cameron, Iberia, Jefferson Davis and 4 more | 84 min |
| Oct 27, 7:55 AM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 13 more | 9 hr |
| Oct 27, 9:44 AM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 7 more | 2 hr |
| Oct 27, 10:08 AM CDT | Tornado Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 6 more | 5 hr |
| Oct 27, 10:59 AM CDT | Mesoscale Discussion | SPC | Beauregard, Vernon | 91 min |
| Oct 27, 12:50 PM CDT | Mesoscale Discussion | SPC | Acadia, Ascension, Assumption, Avoyelles, Concordia, East Baton Rouge and 24 more | 85 min |
| Oct 27, 12:52 PM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 7 more | 83 min |
| Oct 27, 1:53 PM CDT | Tornado Watch | SPC | Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 18 more | 8 hr |
| Oct 27, 3:25 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 13 more | 95 min |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Louisiana, 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.