Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 2075

October 18, 20128 counties in Alabama; 14 parishes in Louisiana; 18 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Oct 18, 2012, 2:40 AM CDT for 8 counties in Alabama; 14 parishes in Louisiana; 18 counties in Mississippi. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued
Oct 18, 2012, 2:40 AM CDT (07:40 UTC)
Expired
Oct 18, 2012, 3:45 AM CDT
In force
65 min
Issued by
the Storm Prediction Center
All 40 counties

Choctaw County, AL, Clarke County, AL, Conecuh County, AL, Escambia County, AL, Marengo County, AL, Monroe County, AL, Washington County, AL, Wilcox County, AL, Ascension Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Clarke County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 7.7 hours before the alert went out and 93 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, Slidell Radar S, LA at 00:00Z on 2012-10-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 518 joules per kilogram.LCLLFCEL10008507005003002001001 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, Slidell Radar S, LA at 00:00Z on 2012-10-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 145 square meters per square second.19395878Sfc1 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
518 J/kg
Mixed-layer CIN
-6 J/kg
Mixed-layer LCL
686 m above ground
0-6 km bulk shear
34 kt
0-1 km storm-relative helicity
145 m²/s²
0-3 km storm-relative helicity
212 m²/s²
Significant tornado parameter
0.3
Supercell composite
2.0

Open this sounding in Storm Lab

The text

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

768 
ACUS11 KWNS 180740
SWOMCD
SPC MCD 180740 
ALZ000-FLZ000-MSZ000-LAZ000-180845-

MESOSCALE DISCUSSION 2075
NWS STORM PREDICTION CENTER NORMAN OK
0240 AM CDT THU OCT 18 2012

AREAS AFFECTED...SERN LA...SERN MS AND SWRN AL

CONCERNING...TORNADO WATCH 668...

VALID 180740Z - 180845Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 668 CONTINUES.

SUMMARY...SEVERE THREAT INCLUDING POTENTIAL FOR ISOLATED DAMAGING
WIND AND A BRIEF TORNADO OR TWO MAY PERSIST THROUGH 10Z.
HOWEVER...THE THREAT IS EXPECTED TO BEGIN A GRADUAL DECREASE...AND
ANOTHER WW WILL PROBABLY NOT BE NEEDED UNLESS TRENDS DICTATE
OTHERWISE.

DISCUSSION...LINE OF SCATTERED STORMS INCLUDING A FEW SUPERCELLS
WILL CONTINUE DEVELOPING SEWD INTO SRN LA...SERN MS AND SWRN AL NEXT
FEW HOURS. HOWEVER...DEEPER FORCING FOR ASCENT AND TRAILING END OF
THE LLJ WILL SHIFT NEWD AWAY FROM THE WARM SECTOR WITH
TIME...RESULTING IN A GRADUAL DECREASE IN 0-3 KM HODOGRAPH SIZE.
WHILE SHEAR/PARAMETER SPACE WILL CONTINUE TO SUPPORT SUPERCELLS WITH
A POTENTIAL FOR ISOLATED DAMAGING WIND AND PERHAPS A BRIEF TORNADO
OR TWO NEXT COUPLE HOURS...THREAT IS NOT EXPECTED TO PERSIST FOR A
LONG ENOUGH DURATION TO WARRANT ANOTHER WW ISSUANCE.

..DIAL/MEAD.. 10/18/2012

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

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

LAT...LON   30559217 31489032 32298852 32248732 31498669 30878739
            30259044 30059196 30559217

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Oct 17, 8:43 PM CDTSevere Thunderstorm WatchSPCColbert, Franklin, Lauderdale4 hr
Oct 17, 11:10 PM CDTMesoscale DiscussionSPCBibb, Blount, Calhoun, Cherokee, Chilton, Coosa and 24 more95 min
Oct 18, 1:09 AM CDTMesoscale DiscussionSPCChoctaw, Clarke, Mobile, Monroe, Washington96 min
Oct 17, 7:01 PM CDTTornado WatchSPCBienville, Bossier, Caddo, Caldwell, Catahoula, Claiborne and 20 more8 hr
Oct 17, 9:28 PM CDTMesoscale DiscussionSPCBienville, Caldwell, Catahoula, Claiborne, Concordia, De Soto and 18 more92 min
Oct 17, 11:49 PM CDTMesoscale DiscussionSPCCaldwell, Catahoula, East Carroll, Franklin, Grant, LaSalle and 6 more86 min
Oct 18, 1:16 AM CDTMesoscale DiscussionSPCAcadia, Allen, Ascension, Assumption, Calcasieu, East Baton Rouge and 12 more59 min
Oct 17, 7:35 PM CDTMesoscale DiscussionSPCBolivar, Coahoma, DeSoto, Panola, Quitman, Tallahatchie and 2 more85 min
Oct 17, 8:07 PM CDTMesoscale DiscussionSPCAlcorn53 min
Oct 17, 8:23 PM CDTTornado WatchSPCAlcorn, Benton, Calhoun, Chickasaw, Itawamba, Lafayette and 8 more5 hr

Nearby

Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Louisiana, 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.