Alert archive / Mississippi / Mesoscale Discussions in 2012
Mesoscale Discussion 317
The Storm Prediction Center issued this mesoscale discussion at Mar 21, 2012, 12:19 PM CDT for 7 parishes in Louisiana; 26 counties in Mississippi. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Mar 21, 2012, 12:19 PM CDT (17:19 UTC)
- Expired
- Mar 21, 2012, 1:45 PM CDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
All 33 counties
Jefferson Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Tammany Parish, LA, Washington Parish, LA, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Hinds County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Leake County, MS, Madison County, MS, Marion County, MS, Newton County, MS, Pearl River County, MS, Perry County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 72 km from the middle of the area, began a volume at 17:21 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
Jackson, MS (KJAN), launched 12:00Z, 5.3 hours before the alert went out and 77 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
- 143 J/kg
- Mixed-layer CIN
- -17 J/kg
- Mixed-layer LCL
- 559 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km storm-relative helicity
- 239 m²/s²
- 0-3 km storm-relative helicity
- 239 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.8
The text
As transmitted, in the capitals the NWS used until 2016.
555
ACUS11 KWNS 211719
SWOMCD
SPC MCD 211719
MSZ000-LAZ000-211845-
MESOSCALE DISCUSSION 0317
NWS STORM PREDICTION CENTER NORMAN OK
1219 PM CDT WED MAR 21 2012
AREAS AFFECTED...FAR EASTERN LA TO CENTRAL/SOUTHERN MS
CONCERNING...TORNADO WATCH 97...
VALID 211719Z - 211845Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 97 CONTINUES.
TORNADO WATCH 97 CONTINUES UNTIL 23Z...WITH CONTINUED POTENTIAL FOR
TORNADOES AND WIND DAMAGE...ESPECIALLY ACROSS FAR SOUTHEAST
LA/SOUTHERN MS.
GENERAL NORTH-SOUTH ORIENTED QUASI-LINEAR CONVECTIVE SYSTEM...WITH
EMBEDDED BOWS/SUPERCELLS...CONTINUES TO GRADUALLY PROGRESS
EAST-NORTHEASTWARD ACROSS SOUTHWEST/WEST-CENTRAL MS AND SOUTHEAST LA
EARLY THIS AFTERNOON. CLOUD BREAKS/STRONGER HEATING ARE EVIDENT
ACROSS EXTREME SOUTHEAST LA INTO SOUTHEAST MS...BUT THE AIRMASS DOES
CONTINUE TO OTHERWISE WARM/MOISTEN INTO CENTRAL MS PER SURFACE
OBSERVATIONAL TRENDS. THE JACKSON MS AND NEW ORLEANS WSR-88D VWPS
ARE BOTH INDICATIVE OF RELATIVELY STRONG/CURVING HODOGRAPHS...WITH
STRONG NEAR-SURFACE SOUTHEASTERLY WINDS BENEATH NEARLY
UNIDIRECTIONAL BUT STRONG DEEP SOUTHERLY FLOW ABOVE 1 KM. WITH A
SURFACE PRESSURE RISE/FALL COUPLET EVIDENT...THIS CONTINUES TO
SUPPORT AN ORGANIZED QUASI-LINEAR CONVECTIVE MODE WITH EMBEDDED
SUPERCELLS/BOWING STRUCTURES AS THE QLCS OTHERWISE SPREADS
EAST-NORTHEAST. THE MOST AGGRESSIVE FORWARD PROPAGATION/PERHAPS A
CORRIDOR OF SEMI-FOCUSED SEVERE MAY CONTINUE TO OCCUR NEAR THE LA/MS
BORDER VICINITY EAST OF I-55...WHERE THE QLCS IS INTERCEPTING
ADDITIONAL WARM ADVECTION SHOWERS/FEW TSTMS IN VICINITY OF A
DIFFERENTIAL HEATING BOUNDARY/INSTABILITY GRADIENT. LASTLY...IN THE
WAKE OF THE QLCS...ADDITIONAL TSTMS HAVE INCREASED ABOUT 75-90 MILES
BEHIND THE PRIMARY CONVECTIVE LINE. THE MAJORITY OF THIS IS
OCCURRING ATOP A SURFACE STABILIZED COLD POOL...WITH SOME HAIL
POSSIBLE.
..GUYER.. 03/21/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MOB...JAN...LIX...
LAT...LON 32899084 33199041 32728921 31088851 29178907 29269046
31029015 32499060 32899084SPC 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, 3:47 PM CDT | Mesoscale Discussion | SPC | Saint Bernard | 88 min |
| Mar 21, 5:40 PM CDT | Mesoscale Discussion | SPC | Orleans, Plaquemines, Saint Bernard | 35 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.