Alert archive / Mississippi / Mesoscale Discussions in 2012
Mesoscale Discussion 794
The Storm Prediction Center issued this mesoscale discussion at May 12, 2012, 10:39 AM CDT for Choctaw County, Mobile County, Washington County, Alabama; 14 parishes in Louisiana; 24 counties in Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 12, 2012, 10:39 AM CDT (15:39 UTC)
- Expired
- May 12, 2012, 12:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 41 counties
Choctaw County, AL, Mobile County, AL, Washington County, AL, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville 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, Tangipahoa Parish, LA, Washington Parish, LA, Amite County, MS, Clarke County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Marion County, MS, Newton County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 3.7 hours before the alert went out and 87 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
- 1685 J/kg
- Mixed-layer CIN
- -13 J/kg
- Mixed-layer LCL
- 500 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 118 m²/s²
- 0-3 km storm-relative helicity
- 201 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 5.7
The text
As transmitted, in the capitals the NWS used until 2016.
080
ACUS11 KWNS 121540
SWOMCD
SPC MCD 121539
ALZ000-MSZ000-LAZ000-121745-
MESOSCALE DISCUSSION 0794
NWS STORM PREDICTION CENTER NORMAN OK
1039 AM CDT SAT MAY 12 2012
AREAS AFFECTED...SERN LA...SRN MS...SWRN AL
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 121539Z - 121745Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...STORMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY
FROM LATE MORNING INTO THE AFTERNOON FROM SERN LA...SERN MS INTO
SWRN AL. THE MAIN THREAT WILL BE ISOLATED DAMAGING WIND. PLANS ARE
TO INCLUDE A LOW END SLIGHT RISK AREA TO ACCOUNT FOR THIS SCENARIO.
WW ISSUANCE WILL ULTIMATELY DEPEND ON CHARACTER AND ORGANIZATION OF
DEVELOPING STORMS.
DISCUSSION...LATE THIS MORNING A COUPLE OF CONVECTIVE INDUCED MCVS
WERE EMBEDDED WITHIN BASE OF LARGER SCALE UPPER TROUGH. ONE WAS
LOCATED OVER SWRN MS MOVING NEWD AND ANOTHER OVER SWRN LA MOVING
EAST. WEAK SFC MESO LOW WAS CENTERED OVER CNTRL LA WITH A WARM FRONT
EXTENDING EWD FROM THE LOW THROUGH SRN MS INTO SWRN AL. OUTFLOW
BOUNDARY EXTENDS SWD FROM THE LOW THROUGH SERN LA INTO THE NWRN
GULF. THE WARM SECTOR IS VERY MOIST WITH NEAR SFC DEWPOINTS IN THE
LOW 70S AND 1.6 INCH PW VALUES. AS THE BOUNDARY LAYER WARMS AND
TEMPERATURES RISE INTO THE LOW 80S...MODERATE INSTABILITY IS
EXPECTED...BUT MLCAPE SHOULD REMAIN GENERALLY AOB 1800 J/KG DUE TO
POOR MID LEVEL LAPSE RATES. WITH A WEAK CAP IN PLACE...STORMS ARE
EXPECTED TO CONTINUE DEVELOPING ALONG RESIDUAL OUTFLOW
BOUNDARIES...THE INLAND PROPAGATING SEA BREEZE...AS WELL AS NEAR THE
WARM FRONT.
BELT OF SLIGHTLY STRONGER FLOW ALONG SRN PERIPHERY OF UPPER LOW IS
CONTRIBUTING TO DEEP LAYER SHEAR FROM 30-35 KT OVER SRN LA INTO THE
BOOTHEEL OF MS AND SWRN AL. DEEP SHEAR IS WEAKER FARTHER TOWARD
CNTRL MS...BUT LOW LEVEL VEERING EXISTS NORTH OF THE WARM FRONT.
OVERALL ENVIRONMENT APPEARS FAVORABLE FOR MULTICELL AND MARGINAL
SUPERCELL STRUCTURES WITH A THREAT OF MAINLY ISOLATED DAMAGING WIND
AS LOW LEVEL LAPSE RATES STEEPEN AND PERHAPS A BRIEF TORNADO OR TWO.
..DIAL/HART.. 05/12/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BMX...MOB...JAN...LIX...LCH...
LAT...LON 31519048 32428951 32388828 31618778 30618817 29768997
29379075 30109145 30999104 31519048SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 12, 5:16 PM CDT | Mesoscale Discussion | SPC | Butler, Choctaw, Clarke, Coffee, Conecuh, Covington and 10 more | 89 min |
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.