Alert archive / Louisiana / Mesoscale Discussions in 2015

Mesoscale Discussion 607

May 11, 201524 parishes in Louisiana; 22 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 11, 2015, 12:30 PM CDT for 24 parishes in Louisiana; 22 counties in Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
May 11, 2015, 12:30 PM CDT (17:30 UTC)
Expired
May 11, 2015, 2:30 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
20%
All 46 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, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Amite County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 5.5 hours before the alert went out and 61 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 12:00Z on 2015-05-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1277 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 12:00Z on 2015-05-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -2 square meters per square second.1939Sfc1 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
1277 J/kg
Mixed-layer CIN
-50 J/kg
Mixed-layer LCL
695 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
-2 m²/s²
0-3 km storm-relative helicity
61 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.2

Open this sounding in Storm Lab

The text

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

142 
ACUS11 KWNS 111731
SWOMCD
SPC MCD 111730 
ALZ000-MSZ000-LAZ000-111930-

MESOSCALE DISCUSSION 0607
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT MON MAY 11 2015

AREAS AFFECTED...SRN MS...SERN LA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 111730Z - 111930Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...SCATTERED STRONG STORMS ARE EXPECTED THROUGH THIS
AFTERNOON WITH MARGINALLY SEVERE WIND OR HAIL POSSIBLE.

DISCUSSION...HEATING HAS RESULTED IN INCREASED INSTABILITY AHEAD OF
A SURGING OUTFLOW BOUNDARY WITH SBCAPE ON THE ORDER OF 2500 J/KG AND
DEWPOINTS INTO THE 70S F. 

LIGHTNING AND RADAR TRENDS INDICATE A RECENT INCREASE IN STORM
INTENSITY FOCUSED ALONG THE OUTFLOW BOUNDARY FROM SWRN MS INTO S
CNTRL LA. WHILE WIND PROFILES ACROSS THE REGION ARE NOT SUPPORTIVE
OF ORGANIZED SEVERE STORMS...FAVORABLE TIME OF DAY COMBINED WITH
SUBSTANTIAL MOISTURE SHOULD LEAD TO ISOLATED SEVERE WIND OR HAIL. AT
THIS TIME...IT APPEARS THE SEVERE THREAT WILL BE TOO ISOLATED FOR A
WATCH.

..JEWELL/CORFIDI.. 05/11/2015

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

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

LAT...LON   29839309 30319178 31119098 31879056 32118988 31968906
            31448867 30888834 30318833 29698846 28968906 28959071
            29379189 29839309

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 10, 7:08 PM CDTMesoscale DiscussionSPCBossier, Caddo97 min
May 10, 9:57 PM CDTMesoscale DiscussionSPCBossier, Caddo93 min
May 10, 11:31 PM CDTTornado WatchSPCBienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 3 more5 hr
May 11, 2:55 AM CDTMesoscale DiscussionSPCSabine95 min
May 11, 1:44 PM CDTMesoscale DiscussionSPCAscension, East Baton Rouge, East Feliciana, Iberville, Livingston, Saint Helena and 3 more2 hr

Nearby

Mesoscale Discussions in Louisiana, 2015Mesoscale Discussions in Mississippi, 2015Every mesoscale discussion in 2015

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.