Alert archive / Alabama / Mesoscale Discussions in 2011

Mesoscale Discussion 438

April 15, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Apr 15, 2011, 1:30 PM CDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Apr 15, 2011, 1:30 PM CDT (18:30 UTC)
Expired
Apr 15, 2011, 3:30 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
All 118 counties

Autauga County, AL, Bibb County, AL, Blount County, AL, Bullock County, AL, Butler County, AL, Calhoun County, AL, Chambers County, AL, Cherokee County, AL, Chilton County, AL, Choctaw County, AL, Clarke County, AL, Clay County, AL, Cleburne County, AL, Conecuh County, AL, Coosa County, AL, Crenshaw County, AL, Cullman County, AL, Dallas County, AL, DeKalb County, AL, Elmore County, AL, Escambia County, AL, Etowah County, AL, Fayette County, AL, Greene County, AL, Hale County, AL, Jackson County, AL, Jefferson County, AL, Lamar County, AL, Lee County, AL, Lowndes County, AL, Macon County, AL, Marengo County, AL, Marion County, AL, Marshall County, AL, Mobile County, AL, Monroe County, AL, Montgomery County, AL, Morgan County, AL, Perry County, AL, Pickens County, AL, Pike County, AL, Randolph County, AL, Shelby County, AL, St. Clair County, AL, Sumter County, AL, Talladega County, AL, Tallapoosa County, AL, Tuscaloosa County, AL, Walker County, AL, Washington County, AL, Wilcox County, AL, Winston County, AL, Carroll County, GA, Haralson County, GA, Heard County, GA, Polk County, GA, Avoyelles Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, Tangipahoa Parish, LA, Tensas Parish, LA, Washington Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Attala County, MS, Chickasaw County, MS, Choctaw County, MS, Claiborne County, MS, Clarke County, MS, Clay County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, George County, MS, Greene County, MS, Hinds County, MS, Holmes County, MS, Jasper County, MS, Jefferson 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, Lowndes County, MS, Madison County, MS, Marion County, MS, Monroe County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Warren County, MS, Wayne County, MS, Webster County, MS, Wilkinson County, MS, Winston County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 126 km from the middle of the area, began a volume at 18:33 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

Jackson, MS (KJAN), launched 12:00Z, 6.5 hours before the alert went out and 135 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-pSkew-T log-p diagram, Jackson, MS at 12:00Z on 2011-04-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1458 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Jackson, MS at 12:00Z on 2011-04-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 382 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
1458 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
523 m above ground
0-6 km bulk shear
59 kt
0-1 km storm-relative helicity
382 m²/s²
0-3 km storm-relative helicity
565 m²/s²
Significant tornado parameter
4.0
Supercell composite
14.6

Open this sounding in Storm Lab

The text

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

029 
ACUS11 KWNS 151831
SWOMCD
SPC MCD 151830
GAZ000-ALZ000-FLZ000-MSZ000-LAZ000-152030-

MESOSCALE DISCUSSION 0438
NWS STORM PREDICTION CENTER NORMAN OK
0130 PM CDT FRI APR 15 2011

AREAS AFFECTED...PORTIONS MS...CENTRAL-ERN LA...AL...EXTREME WRN GA.

CONCERNING...TORNADO WATCH 140...141...

VALID 151830Z - 152030Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 140...141...CONTINUES.

CONTINUE W 141.  REPLACEMENT WW FOR 140 IS LIKELY BEFORE SCHEDULED
20Z EXPIRATION...BECAUSE SVR THREAT WILL PERSIST WELL BEYOND THAT
TIME AND PRIOR TO COLD FROPA.

18Z SFC MESOANALYSIS SHOWED COLD FRONT CONTINUING TO MOVE EWD ACROSS
NERN...CENTRAL AND SWRN LA...WITH WARM FRONT ANALYZED ROUGHLY 30 NNE
TCL...TCL...GZH...NSE AND LIFTING NEWD ACROSS W-CENTRAL/S-CENTRAL
AL.  PRE COLD-FRONTAL CONFLUENCE LINE IS PIVOTING EWD ACROSS
SWRN/CENTRAL MS WHILE DRIFTING EWD ACROSS SERN LA.  AS THESE
PROCESSES CONTINUES...FAVORABLY BUOYANT AND STRONGLY HEATED AIR
MASS...CHARACTERIZED BY MLCAPE 1000-2000 J/KG...WILL OVERSPREAD
PROGRESSIVELY MORE OF CENTRAL/SRN AND EVENTUALLY ERN AL...THROUGH
LATE AFTERNOON.  NRN FRINGE OF STRONGEST HEATING IS EVIDENT IN SFC
DATA AND VIS IMAGERY ROUGHLY ALONG JAN-EET LINE...AND HAS MOVED N OF
MEI.  STORMS WITHIN AND JUST N OF THAT BOUNDARY MAY ENCOUNTER
ENHANCED LOW-LEVEL VORTICITY/ASCENT.  THIS INCLUDES LONG-LIVED
SUPERCELL NOW MOVING TOWARD PORTIONS SUMTER/GREENE/HALE/TUSCALOOSA
COUNTIES AL THAT PRODUCED DAMAGING TORNADO IN JAN AREA AROUND
16Z...AND MORE RECENTLY...REPORT OF LARGE TORNADO IN KEMPER COUNTY
AT 1820Z.  UPSHEAR SUPERCELLS S AND SW JAN ALSO MAY INTERACT WITH
THAT BOUNDARY.  CELLS OVER SERN MS AND SRN AL MAY ENCOUNTER WARM
FRONT...WHERE LOW-LEVEL BACKING/VORTICITY/HODOGRAPHS WILL BE
RELATIVELY MAXIMIZED.  BOTH REGIMES MAY SUPPORT CORRIDORS OF LOCALLY
ENHANCED TORNADO POTENTIAL...WITH EFFECTIVE SRH REACHING 500 J/KG.
HOWEVER...STG LOW-MIDLEVEL SPEED SHEAR WILL SUPPORT SUPERCELL THREAT
EVEN AS FAR W AS S-CENTRAL LA.

SVR POTENTIAL MAY EXTEND INTO PORTIONS WRN GA DURING NEXT 2-3 HOURS
WITH CELLS WELL NE OF SFC WARM FRONT...BUT IN REGIME OF ELEVATED WAA
AND STRENGTHENING BUOYANCY/SHEAR ALOFT...SUPPORTING OCNL HAIL.
BETTER-ORGANIZED THREAT THERE IS NOT EXPECTED UNTIL LATE AFTERNOON
INTO EVENING.

..EDWARDS.. 04/15/2011

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

ATTN...WFO...FFC...TAE...BMX...HUN...MOB...MEG...JAN...LIX...
LCH...SHV...

LAT...LON   31109248 32009153 33558978 34078871 34338761 34908581
            33858503 32708523 31548577 31108703 30958751 30488839
            30459014 30569233 31109248

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 15, 4:21 AM CDTMesoscale DiscussionSPCColbert, Franklin, Lamar, Lauderdale, Marion, Pickens84 min
Apr 15, 7:32 AM CDTTornado WatchSPCBlount, Choctaw, Clarke, Colbert, Cullman, Fayette and 20 more7 hr
Apr 15, 10:28 AM CDTMesoscale DiscussionSPCAutauga, Baldwin, Bibb, Blount, Butler, Chilton and 34 more2 hr
Apr 15, 11:21 AM CDTTornado WatchSPCAutauga, Baldwin, Barbour, Bibb, Blount, Bullock and 44 more9 hr
Apr 15, 3:35 PM CDTMesoscale DiscussionSPCAutauga, Bibb, Blount, Bullock, Butler, Chambers and 39 more85 min
Apr 15, 5:57 PM CDTMesoscale DiscussionSPCColbert, Franklin, Lamar, Lauderdale, Lawrence, Marion2 hr
Apr 15, 4:30 PM CDTMesoscale DiscussionSPCBarrow, Bartow, Butts, Carroll, Cherokee, Clayton and 26 more60 min
Apr 15, 4:46 PM CDTTornado WatchSPCBanks, Barrow, Bartow, Butts, Carroll, Chattooga and 45 more3 hr
Apr 14, 11:24 PM CDTSevere Thunderstorm WatchSPCBossier, Caddo, Claiborne, De Soto, Webster3 hr
Apr 14, 11:56 PM CDTMesoscale DiscussionSPCBossier, Caddo, De Soto, Webster94 min
Apr 15, 1:27 AM CDTMesoscale DiscussionSPCBienville, Bossier, Claiborne, East Carroll, Jackson, Lincoln and 5 more93 min
Apr 15, 2:19 AM CDTTornado WatchSPCBienville, Bossier, Caddo, Caldwell, Catahoula, Claiborne and 20 more8 hr
Apr 15, 2:41 PM CDTTornado WatchSPCAcadia, Ascension, Assumption, Avoyelles, Concordia, East Baton Rouge and 19 more7 hr
Apr 15, 6:09 PM CDTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 12 more96 min
Apr 15, 12:29 PM CDTMesoscale DiscussionSPCAlcorn, Benton, DeSoto, Lafayette, Marshall, Panola and 4 more61 min
Apr 15, 2:09 PM CDTTornado WatchSPCAlcorn, Benton, Calhoun, Chickasaw, DeSoto, Itawamba and 13 more7 hr

Nearby

Mesoscale Discussions in Alabama, 2011Mesoscale Discussions in Mississippi, 2011Mesoscale Discussions in Louisiana, 2011Every mesoscale discussion in 2011

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.