Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 322

March 21, 2012Plaquemines Parish, Saint Bernard Parish, Louisiana; 14 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Mar 21, 2012, 9:27 PM CDT for Plaquemines Parish, Saint Bernard Parish, Louisiana; 14 counties in Mississippi. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued
Mar 21, 2012, 9:27 PM CDT (02:27 UTC)
Expired
Mar 21, 2012, 11:00 PM CDT
In force
93 min
Issued by
the Storm Prediction Center

Counties Plaquemines Parish, LA, Saint Bernard Parish, LA, Clarke County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jones County, MS, Lauderdale County, MS, Newton County, MS, Perry County, MS, Stone County, MS, Wayne County, MS

The radar

The Mobile radar (KMOB), 90 km from the middle of the area, began a volume at 02:28 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 nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 2.5 hours before the alert went out and 67 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 2012-03-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 131 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 2012-03-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -10 square meters per square second.193958Sfc1 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
131 J/kg
Mixed-layer CIN
-28 J/kg
Mixed-layer LCL
505 m above ground
0-6 km bulk shear
33 kt
0-1 km storm-relative helicity
-10 m²/s²
0-3 km storm-relative helicity
17 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6

Open this sounding in Storm Lab

The text

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

245 
ACUS11 KWNS 220228
SWOMCD
SPC MCD 220227
ALZ000-MSZ000-LAZ000-220400-

MESOSCALE DISCUSSION 0322
NWS STORM PREDICTION CENTER NORMAN OK
0927 PM CDT WED MAR 21 2012

AREAS AFFECTED...SERN LA AND SERN TO EAST CENTRAL MS

CONCERNING...TORNADO WATCH 98...

VALID 220227Z - 220400Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 98 CONTINUES.

IN ADDITION TO THE CONTINUED SEVERE WEATHER THREAT...HEAVY RAINFALL
RATES PER HIGH PW VALUES /IN EXCESS OF 1.75 INCH/ WILL BE LIKELY
THROUGH THE LATE EVENING AS STORMS CONTINUE TO TRAIN TOWARD THE
NNE...WITHIN A LOW LEVEL CONVERGENCE ZONE IN SERN MS.

MID EVENING OBJECTIVE ANALYSES INDICATED THE STRONGEST LOW LEVEL
CONVERGENCE EXTENDED FROM FAR SERN LA AND ADJACENT COASTAL WATERS
NWD THROUGH SERN TO EAST CENTRAL MS.  THIS CONVERGENCE ZONE IS
JUXTAPOSED WITH THE RIGHT ENTRANCE REGION OF A 120+ KT SSELY UPPER
LEVEL JET PER 00Z SOUNDING ANALYSIS.  THESE FACTORS COMBINED WITH
RICH DEEP LAYER MOISTURE /PW OF 1.81 PER 00Z SLIDELL LA SOUNDING/
AND MUCAPE OF 500-1000 J/KG WILL CONTINUE TO FAVOR ADDITIONAL TSTM
DEVELOPMENT INTO THE LATE EVENING.  AT 0215Z...REGIONAL RADAR
IMAGERY SHOWED A BAND OF TSTMS LOCATED WITHIN THIS CONVERGENT
ZONE...WITH THE STORMS EXTENDING NNEWD FROM ERN PLAQUEMINES PARISH
THROUGH SERN MS TO THE NERN PART OF WW 98 IN EAST CENTRAL MS.

DESPITE THE MARGINAL INSTABILITY...THE SLIDELL LA SOUNDING MODIFIED
FOR CURRENT SURFACE OBSERVATIONS IN SERN MS INDICATED THAT PARCELS
REMAIN SURFACE BASED.  GIVEN SSELY LOW LEVEL WINDS BENEATH 50 KT
SSWLY MIDLEVEL WINDS ACROSS WW 98...EFFECTIVE BULK SHEAR AROUND 35
KT AND EFFECTIVE SRH OF 200-300 M2/S2 SUPPORT A CONTINUED POTENTIAL
FOR A TORNADO THREAT.

..PETERS.. 03/22/2012

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

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

LAT...LON   28618914 29118945 29438973 30268956 31188945 32048947
            32608948 32598837 31828850 30248827 29758830 29238864
            28898866 28678885 28618914

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Mar 21, 11:49 PM CDTMesoscale DiscussionSPCSaint Bernard56 min
Mar 22, 2:28 AM CDTMesoscale DiscussionSPCGeorge, Greene, Jackson2 hr
Mar 22, 6:49 AM CDTMesoscale DiscussionSPCGeorge, Jackson116 min
Mar 22, 7:15 AM CDTTornado WatchSPCGeorge, Harrison, Jackson, Stone5 hr
Mar 22, 9:53 AM CDTMesoscale DiscussionSPCJackson67 min

Nearby

Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Louisiana, 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; radar from the NEXRAD Level II archive.