Alert archive / Mississippi / Mesoscale Discussions in 2009

Mesoscale Discussion 310

March 28, 200920 parishes in Louisiana; 23 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Mar 28, 2009, 1:33 AM CDT for 20 parishes in Louisiana; 23 counties in Mississippi. It was in force for 27 min.

The area

The outline as issued.

The facts

Issued: Mar 28, 2009, 1:33 AM CDT (06:33 UTC)
Expired: Mar 28, 2009, 2:00 AM CDT
In force: 27 min
Issued by: the Storm Prediction Center

All 43 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Amite County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Leake County, MS, Lincoln County, MS, Marion County, MS, Neshoba County, MS, Newton County, MS, Pearl River County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Walthall County, MS

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 86Mar 28, 2:15 AM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 6.6 hours before the alert went out and 74 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1844 J/kg
Mixed-layer CIN: -27 J/kg
Mixed-layer LCL: 467 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: 259 m²/s²
0-3 km storm-relative helicity: 296 m²/s²
Significant tornado parameter: 2.8
Supercell composite: 13.4

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
ACUS11 KWNS 280633
SWOMCD
SPC MCD 280633 
ALZ000-MSZ000-LAZ000-280700-

MESOSCALE DISCUSSION 0310
NWS STORM PREDICTION CENTER NORMAN OK
0133 AM CDT SAT MAR 28 2009

AREAS AFFECTED...SERN LA/CENTRAL AND SRN MS

CONCERNING...TORNADO WATCH 83...

VALID 280633Z - 280700Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 83 CONTINUES.

WW 82 WILL NEED TO BE EITHER EXTENDED IN TIME BEYOND THE SCHEDULED
07Z EXPIRATION OR A NEW WW WILL BE ISSUED TO REPLACE WW 82.

TRENDS IN REGIONAL RADARS ACROSS THE LOWER MS VALLEY INDICATED
ACTIVITY FROM SERN LA INTO PARTS OF CENTRAL MS ARE EVOLVING INTO A
MORE LINEAR TYPE SYSTEM.  THIS SCENARIO IS EXPECTED AS MID-UPPER
LEVEL FLOW/EFFECTIVE SHEAR VECTORS BACK ACROSS THIS REGION WITH THE
APPROACH OF THE SRN PLAINS CLOSED LOW.  A CONTINUED INFLUX OF GULF
MOISTURE NWD ALONG SLY LLJ WITHIN WARM SECTOR WILL MAINTAIN AN
UNSTABLE ENVIRONMENT CONDUCIVE FOR ADDITIONAL TSTMS.  LOW LEVEL
SHEAR IS EXPECTED TO REMAIN STRONG...GIVEN BACKED SELY SURFACE WINDS
BENEATH SLY LLJ.

..PETERS.. 03/28/2009

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BMX...MOB...JAN...LIX...LCH...

LAT...LON   29279211 31629064 33028977 32918824 30018975 29259003
            28919052 29279211

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 27, 7:51 PM CDT	Tornado Watch	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Calcasieu and 36 more	9 hr
Mar 27, 8:21 PM CDT	Mesoscale Discussion	SPC	Orleans, Saint Bernard, Saint Tammany, Washington	84 min
Mar 27, 10:24 PM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Claiborne, De Soto, East Carroll and 13 more	96 min
Mar 27, 11:06 PM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Caldwell and 32 more	84 min
Mar 27, 11:51 PM CDT	Mesoscale Discussion	SPC	Saint Bernard	84 min
Mar 28, 4:25 AM CDT	Mesoscale Discussion	SPC	Saint Bernard, Saint Tammany	35 min
Mar 27, 10:09 PM CDT	Tornado Watch	SPC	George, Greene, Hancock, Harrison, Jackson, Perry and 2 more	9 hr
Mar 28, 2:20 AM CDT	Tornado Watch	SPC	Clarke, Covington, Forrest, Jasper, Jefferson Davis, Jones and 10 more	3 hr
Mar 28, 3:14 AM CDT	Mesoscale Discussion	SPC	George, Greene, Harrison, Jackson, Perry, Stone and 1 more	61 min
Mar 28, 4:50 AM CDT	Tornado Watch	SPC	George, Greene, Perry, Stone, Wayne	5 hr

Nearby

Mesoscale Discussions in Mississippi, 2009 Mesoscale Discussions in Louisiana, 2009 Every mesoscale discussion in 2009

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.