Alert archive / Mississippi / Mesoscale Discussions in 2012
Mesoscale Discussion 1836
The Storm Prediction Center issued this mesoscale discussion at Aug 29, 2012, 8:21 PM CDT for Baldwin County, Mobile County, Washington County, Alabama; 18 parishes in Louisiana; 30 counties in Mississippi. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Aug 29, 2012, 8:21 PM CDT (01:21 UTC)
- Expired
- Aug 29, 2012, 9:45 PM CDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
All 51 counties
Baldwin County, AL, Mobile County, AL, Washington County, AL, Ascension Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS, Wilkinson 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 00:00Z, 1.4 hours before the alert went out and 35 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
- 408 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 464 m above ground
- 0-6 km bulk shear
- 55 kt
- 0-1 km storm-relative helicity
- 299 m²/s²
- 0-3 km storm-relative helicity
- 301 m²/s²
- Significant tornado parameter
- 0.8
- Supercell composite
- 6.3
The text
As transmitted, in the capitals the NWS used until 2016.
721
ACUS11 KWNS 300121
SWOMCD
SPC MCD 300121
ALZ000-FLZ000-MSZ000-LAZ000-300245-
MESOSCALE DISCUSSION 1836
NWS STORM PREDICTION CENTER NORMAN OK
0821 PM CDT WED AUG 29 2012
AREAS AFFECTED...SE LA...SRN MS...SW AL
CONCERNING...TORNADO WATCH 595...
VALID 300121Z - 300245Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 595 CONTINUES.
SUMMARY...A TORNADO THREAT WILL LIKELY CONTINUE ACROSS SE LA...SRN
MS AND SW AL LATE THIS EVENING. THE TORNADO THREAT SHOULD GRADUALLY
DEVELOP NWD WITH ROTATING STORMS THAT PERSIST WITHIN THE BANDS OF
ISAAC.
DISCUSSION...THE CENTER OF TROPICAL STORM ISAAC IS CURRENTLY JUST
SOUTH OF BATON ROUGE AND THE NATIONAL HURRICANE CENTER FORECASTS THE
SYSTEM TO CONTINUE MOVING NWWD FOR THE REMAINDER OF THIS EVENING.
RAINBANDS EXTEND FROM 175 TO 200 STATUTE MILES TO THE NORTH AND EAST
OF THE CENTER. MESOANALYSIS CURRENTLY SHOWS THE AXIS OF STRONGEST
LOW-LEVEL WINDS WRAPPING EWD AND SWD ACROSS THE NERN QUADRANT OF
ISAAC ABOUT 100 STATUTE MILES AWAY FROM THE CENTER. THIS IS CREATING
STRONG LOW-LEVEL SHEAR WHICH IS SAMPLED WELL BY THE NEW ORLEANS 00Z
SOUNDING WITH 0-1 KM STORM RELATIVE HELICITIES OF 300 TO 325 M2/S2.
THIS COMBINED WITH LCL HEIGHTS VERY CLOSE TO GROUND LEVEL AND SFC
DEWPOINTS IN THE UPPER 70S F SHOULD CONTINUE TO BE FAVORABLE FOR
LOW-ROTATING CLOUD BASES AND TORNADO FORMATION. THE GREATEST CHANCE
FOR TORNADO DEVELOPMENT WILL LIKELY OCCUR WITH INDIVIDUAL CELL
ELEMENTS EMBEDDED IN THE MORE INTENSE RAINBANDS TO THE NORTHEAST OF
THE CENTER OF ISAAC.
..BROYLES.. 08/30/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MOB...JAN...LIX...LCH...
LAT...LON 28868871 28668896 28648931 28608959 28888982 28789008
29099011 29189001 29329018 29329001 29459014 29629018
29729034 29919063 30169067 30099118 30139147 30449174
30839182 31069169 30989159 31189162 31299161 31269147
31409154 31459149 31559149 31549140 31619152 31629139
31839136 31819125 32009108 32069115 32229071 32049069
32048973 32238973 32238844 31718846 31708810 31588810
31548794 31298791 31108795 31298777 31308760 30998759
30818760 30648738 30458742 30298749 30328723 29968713
29838818 29898826 29858845 29608853 29418867 29138860
28868871SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 29, 11:06 PM CDT | Mesoscale Discussion | SPC | Baldwin, Mobile, Washington | 84 min |
| Aug 29, 11:42 PM CDT | Tornado Watch | SPC | Mobile, Washington | 8 hr |
| Aug 30, 3:18 AM CDT | Mesoscale Discussion | SPC | Baldwin, Butler, Choctaw, Clarke, Coffee, Conecuh and 7 more | 117 min |
| Aug 30, 6:33 AM CDT | Mesoscale Discussion | SPC | Baldwin, Butler, Choctaw, Clarke, Coffee, Conecuh and 13 more | 117 min |
| Aug 30, 7:13 AM CDT | Tornado Watch | SPC | Autauga, Baldwin, Butler, Choctaw, Clarke, Conecuh and 15 more | 9 hr |
| Aug 30, 12:57 PM CDT | Mesoscale Discussion | SPC | Baldwin, Butler, Choctaw, Clarke, Conecuh, Dallas and 8 more | 93 min |
| Aug 30, 3:56 PM CDT | Tornado Watch | SPC | Choctaw, Greene, Sumter, Washington | 6 hr |
Nearby
Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Alabama, 2012Every mesoscale discussion in 2012
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.