Alert archive / Louisiana / Mesoscale Discussions in 2012
Mesoscale Discussion 1829
The Storm Prediction Center issued this mesoscale discussion at Aug 28, 2012, 5:48 PM CDT for 4 states. It was in force for 87 min.
The area
The outline as issued.
The facts
- Issued
- Aug 28, 2012, 5:48 PM CDT (22:48 UTC)
- Expired
- Aug 28, 2012, 7:15 PM CDT
- In force
- 87 min
- Issued by
- the Storm Prediction Center
All 38 counties
Baldwin County, AL, Conecuh County, AL, Covington County, AL, Escambia County, AL, Mobile County, AL, Monroe County, AL, Washington County, AL, Bay County, FL, Escambia County, FL, Holmes County, FL, Okaloosa County, FL, Santa Rosa County, FL, Walton County, FL, Washington County, FL, Jefferson Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, Forrest County, MS, George County, MS, Greene 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, Wayne County, MS
The radar
The Mobile radar (KMOB), 79 km from the middle of the area, began a volume at 22:51 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, 10.8 hours before the alert went out and 102 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
- 41 J/kg
- Mixed-layer CIN
- -110 J/kg
- Mixed-layer LCL
- 650 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 272 m²/s²
- 0-3 km storm-relative helicity
- 266 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
788
ACUS11 KWNS 282249
SWOMCD
SPC MCD 282248
FLZ000-ALZ000-MSZ000-LAZ000-290015-
MESOSCALE DISCUSSION 1829
NWS STORM PREDICTION CENTER NORMAN OK
0548 PM CDT TUE AUG 28 2012
AREAS AFFECTED...PARTS OF SRN LA...SRN MS...SRN AL AND THE WRN FL
PANHANDLE
CONCERNING...TORNADO WATCH 591...592...
VALID 282248Z - 290015Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 591...592...CONTINUES.
SUMMARY...RISK FOR ISOLATED TORNADOES WILL CONTINUE WITHIN TORNADO
WATCH AREAS THIS EVENING...A NEW TORNADO WATCH WILL BE ISSUED PRIOR
TO THE SCHEDULED 00Z EXPIRATION OF WWS 591 AND 592.
DISCUSSION...ISAAC IS NOW CENTERED NEAR SOUTHEASTERN LOUISIANA
COASTAL PARISHES AND EXPECTED TO ONLY VERY SLOWLY DRIFT
NORTHWESTWARD/WESTWARD THROUGH THE EVENING HOURS. MODELS ARE
SUGGESTIVE THAT THIS MAY OCCUR AS A STRONGER SOUTHEASTERLY LOW-LEVEL
JET CORE CONTINUES TO GRADUALLY PROPAGATE AROUND ITS EASTERN AND
NORTHERN PERIPHERY... INLAND ACROSS SOUTHEASTERN LOUISIANA/SOUTHERN
MISSISSIPPI/SOUTHERN ALABAMA AND ADJACENT WESTERN FLORIDA PANHANDLE
COASTAL AREAS. THIS MAY BE ACCOMPANIED BY AN INFLUX OF AT LEAST
SLIGHTER HIGHER BOUNDARY LAYER DEW POINTS...MAINTAINING OR SLIGHTLY
INCREASING NEAR SURFACE INSTABILITY DESPITE THE ONSET OF SUBTLE
NOCTURNAL SURFACE COOLING. IT MAY NOT BE OUT OF THE QUESTION THAT
THE COMBINATION OF STRENGTHENING LOW-LEVEL SHEAR AND INCREASING
BOUNDARY LAYER RELATIVE HUMIDITY COULD STILL SUPPORT AT LEAST SOME
INCREASE IN TORNADIC POTENTIAL THROUGH THE 03-06Z TIME FRAME...
MAINLY ACROSS AREAS NOW COVERED BY TORNADO WATCHES 591 AND 592.
..KERR/CORFIDI.. 08/28/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...TAE...MOB...JAN...LIX...
LAT...LON 29339097 29949106 31099027 31628905 31718811 31518678
30988559 29838548 29908647 29848758 29608810 28768896
28638980 28999072 29339097SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 28, 7:01 AM CDT | Mesoscale Discussion | SPC | Baldwin, Clarke, Coffee, Conecuh, Covington, Escambia and 4 more | 2 hr |
| Aug 28, 9:46 AM CDT | Tornado Watch | SPC | Baldwin, Choctaw, Clarke, Conecuh, Escambia, Mobile and 2 more | 9 hr |
| Aug 28, 12:37 PM CDT | Mesoscale Discussion | SPC | Baldwin, Escambia, Mobile, Washington | 83 min |
| Aug 28, 3:46 PM CDT | Mesoscale Discussion | SPC | Baldwin, Clarke, Escambia, Mobile, Monroe, Washington | 89 min |
| Aug 28, 6:47 PM CDT | Tornado Watch | SPC | Baldwin, Choctaw, Clarke, Conecuh, Escambia, Mobile and 2 more | 21 hr |
| Aug 28, 12:56 PM CDT | Tornado Watch | SPC | Covington, Forrest, Jefferson Davis, Jones, Lamar, Lawrence and 2 more | 6 hr |
Nearby
Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Mississippi, 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; radar from the NEXRAD Level II archive.