Alert archive / Mississippi / Mesoscale Discussions in 2012
Mesoscale Discussion 321
The Storm Prediction Center issued this mesoscale discussion at Mar 21, 2012, 5:40 PM CDT for Orleans Parish, Plaquemines Parish, Saint Bernard Parish, Louisiana; 23 counties in Mississippi. It was in force for 35 min.
The area
The outline as issued.
The facts
- Issued
- Mar 21, 2012, 5:40 PM CDT (22:40 UTC)
- Expired
- Mar 21, 2012, 6:15 PM CDT
- In force
- 35 min
- Issued by
- the Storm Prediction Center
All 26 counties
Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Clarke County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Leake County, MS, Marion County, MS, Neshoba County, MS, Newton County, MS, Pearl River County, MS, Perry County, MS, Scott County, MS, Smith County, MS, Stone County, MS, Wayne County, MS
The radar
The Mobile radar (KMOB), 99 km from the middle of the area, began a volume at 22:39 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, 10.7 hours before the alert went out and 67 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
- 983 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 519 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 363 m²/s²
- 0-3 km storm-relative helicity
- 421 m²/s²
- Significant tornado parameter
- 1.7
- Supercell composite
- 10.7
The text
As transmitted, in the capitals the NWS used until 2016.
142
ACUS11 KWNS 212240
SWOMCD
SPC MCD 212240
ALZ000-MSZ000-LAZ000-212315-
MESOSCALE DISCUSSION 0321
NWS STORM PREDICTION CENTER NORMAN OK
0540 PM CDT WED MAR 21 2012
AREAS AFFECTED...PARTS OF CENTRAL/SRN MS AND FAR SERN LA
CONCERNING...TORNADO WATCH 97...
VALID 212240Z - 212315Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 97 CONTINUES.
A NEW TORNADO WATCH WILL LIKELY BE NEEDED INTO THE EVENING FOR PARTS
OF CENTRAL/SRN MS AND FAR SERN LA.
AT 2225Z...REGIONAL RADAR IMAGERY SHOWED AN AREA OF TSTMS /WITH
STRONGER REFLECTIVITY/ OVER SERN TO EAST CENTRAL MS...AND A SECOND
AREA OF TSTMS EXTENDING FROM SW-NW OF NEW ORLEANS INTO SWRN/CENTRAL
MS. THE FORMER BAND OF TSTMS IS LOCATED WITHIN A ZONE OF LOW LEVEL
CONVERGENCE EXTENDING FROM S-N...WITH MESO-ANALYSIS SUGGESTING AN
AREA OF LOW PRESSURE OVER SOUTH CENTRAL MS/ADJACENT SERN LA /JUST SW
OF THE RECENT TORNADO WARNING ISSUED BY WFO JAN/. SELY LOW LEVEL
WINDS /PER WSR-88D VADS AND ONE WIND PROFILER IN THE GULF COAST
STATES/ COMBINED WITH SSWLY 50+ KT MIDLEVEL WINDS IS MAINTAINING
EFFECTIVE BULK SHEAR OF 30-40 KT. THIS COMBINED WITH SFC-1 KM SHEAR
OF 25-35 KT REMAIN SUFFICIENT FOR ORGANIZED STORMS WITH A TORNADO
THREAT.
MOST MODEL DATA SUGGESTS THERE COULD BE A TEMPORARY LULL IN THE
NUMBER OF STRONGER TSTMS. HOWEVER...GIVEN THE FAVORABLE KINEMATICS
AND MODELS INDICATING AN INCREASE IN VERTICAL MOTION OVER THIS
REGION THIS EVENING...A NEW TORNADO WATCH ISSUANCE IS LIKELY.
..PETERS.. 03/21/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BMX...MOB...JAN...LIX...
LAT...LON 29729003 31088985 32488977 32938971 32958822 31288839
30208840 29508893 29038915 29108954 29729003SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 20, 8:02 PM CDT | Tornado Watch | SPC | Beauregard, Calcasieu, Cameron, Vernon | 4 hr |
| Mar 20, 10:23 PM CDT | Mesoscale Discussion | SPC | Allen, Beauregard, Calcasieu, Jefferson Davis, Natchitoches, Vernon | 67 min |
| Mar 20, 10:59 PM CDT | Tornado Watch | SPC | Acadia, Allen, Beauregard, Bienville, Calcasieu, Caldwell and 17 more | 7 hr |
| Mar 21, 2:17 AM CDT | Mesoscale Discussion | SPC | Acadia, Avoyelles, Caldwell, Catahoula, Concordia, Evangeline and 17 more | 118 min |
| Mar 21, 4:38 AM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 19 more | 97 min |
| Mar 21, 5:04 AM CDT | Tornado Watch | SPC | Acadia, Ascension, Assumption, Avoyelles, Caldwell, Catahoula and 33 more | 7 hr |
| Mar 21, 7:48 AM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, Avoyelles, East Baton Rouge, East Feliciana, Iberville and 10 more | 87 min |
| Mar 21, 9:25 AM CDT | Mesoscale Discussion | SPC | Ascension, Concordia, East Baton Rouge, East Carroll, East Feliciana, Franklin and 17 more | 95 min |
| Mar 21, 10:07 AM CDT | Tornado Watch | SPC | Ascension, East Carroll, East Feliciana, Franklin, Jefferson, Lafourche and 17 more | 8 hr |
| Mar 21, 12:19 PM CDT | Mesoscale Discussion | SPC | Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Tammany and 1 more | 86 min |
| Mar 21, 3:47 PM CDT | Mesoscale Discussion | SPC | Saint Bernard | 88 min |
| Mar 21, 6:02 PM CDT | Tornado Watch | SPC | Plaquemines, Saint Bernard | 9 hr |
Nearby
Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Louisiana, 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.