Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 74

January 26, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Jan 26, 2012, 7:29 AM CST for 4 states. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Jan 26, 2012, 7:29 AM CST (13:29 UTC)
Expired: Jan 26, 2012, 9:00 AM CST
In force: 91 min
Issued by: the Storm Prediction Center

All 23 counties

Baldwin County, AL, Choctaw County, AL, Clarke County, AL, Conecuh County, AL, Escambia County, AL, Mobile County, AL, Monroe County, AL, Washington County, AL, Wilcox County, AL, Escambia County, FL, Santa Rosa County, FL, Plaquemines Parish, LA, Saint Bernard Parish, LA, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River 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 13:29 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.

Tornado Watch 18Jan 26, 9:55 AM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 1.5 hours before the alert went out and 81 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1176 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 461 m above ground
0-6 km bulk shear: 55 kt
0-1 km storm-relative helicity: 354 m²/s²
0-3 km storm-relative helicity: 359 m²/s²
Significant tornado parameter: 2.6
Supercell composite: 10.4

Open this sounding in Storm Lab

The text

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

133 
ACUS11 KWNS 261330
SWOMCD
SPC MCD 261329
ALZ000-FLZ000-MSZ000-LAZ000-261500-

MESOSCALE DISCUSSION 0074
NWS STORM PREDICTION CENTER NORMAN OK
0729 AM CST THU JAN 26 2012

AREAS AFFECTED...PORTIONS SERN MS...EXTREME SERN LA...SWRN
AL...EXTREME WRN PANHANDLE OF FL.

CONCERNING...TORNADO WATCH 17...

VALID 261329Z - 261500Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 17 CONTINUES.

STEADY INCREASE IN ORGANIZATION OF PRIMARY CONVECTIVE BAND HAS BEEN
EVIDENT DURING PAST HOUR...AND SVR POTENTIAL APPEARS TO BE
INCREASING CORRESPONDINGLY.  LEWP/BOW FEATURES WITHIN QLCS...AS WELL
AS ANY SUSTAINED/DISCRETE CELLS AHEAD OF IT...MAY OFFER POTENTIAL
FOR TORNADIC MESOCIRCULATIONS.  DAMAGING GUSTS ALSO ARE POSSIBLE
MAINLY NEAR APEXES OF OUTFLOW ARCS.

IMPROVED ORGANIZATION APPEARS TO BE RELATED TO STRENGTHENING
DEEP-LAYER ASCENT AT VARIOUS SCALES...INCLUDING LARGE-SCALE SUPPORT
AHEAD OF EJECTING TX SHORTWAVE TROUGH..AND LOW-LEVEL CONVERGENCE
PRECEDING SFC COLD FRONT.  THROUGH REMAINDER FORENOON
HOURS...COMBINATION OF LOW-LEVEL WAA AND SUBTLE DIABATIC HEATING
SHOULD BOOST MLCAPE IN WARM SECTOR...WITH RANGES FROM ABOUT 250 J/KG
OVER NERN FRINGES OF WW AREA TO 1000-1500 J/KG ALONG COAST....BASED
ON MODIFIED 12Z LIX RAOB AND FCST SOUNDINGS.  VERTICAL SHEAR WILL
REMAIN FAVORABLE...WITH EFFECTIVE SRH IN 200-400 J/KG RANGE AND
EFFECTIVE SHEAR MAGNITUDES INCREASING AGAIN TO 45-55 KT MOST AREAS.
STRONGLY PARALLEL COMPONENT OF MEAN FLOW WITH REGARD TO PREFRONTAL
BOUNDARY WILL SUPPORT CONTINUANCE OF QUASI-LINEAR MODE...THOUGH WEAK
CINH AHEAD OF MAIN MCS INDICATES POTENTIAL FOR ADDITIONAL SUPERCELL
FORMATION ASIDE FROM THAT CROSSING PLAQUEMINES PARISH AS OF 1320Z.

..EDWARDS.. 01/26/2012

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

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

LAT...LON   29219002 29988990 30748969 31448927 31798901 32208838
            32228797 32108715 31668681 30398682 30228766 30228832
            30228853 30228888 30118915 30108890 29928880 29678887
            29488907 29388926 29258910 29178894 29048916 28928912
            29088924 28838948 29118938 29268959 29298987 29219002

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 26, 2:05 AM CST	Mesoscale Discussion	SPC	Mobile, Washington	2 hr
Jan 26, 4:18 AM CST	Tornado Watch	SPC	Baldwin, Choctaw, Clarke, Conecuh, Escambia, Mobile and 3 more	7 hr
Jan 26, 9:34 AM CST	Mesoscale Discussion	SPC	Autauga, Baldwin, Barbour, Bullock, Butler, Calhoun and 24 more	86 min
Jan 26, 9:55 AM CST	Tornado Watch	SPC	Autauga, Baldwin, Barbour, Bibb, Bullock, Butler and 34 more	7 hr
Jan 26, 2:16 PM CST	Mesoscale Discussion	SPC	Barbour, Dale, Henry, Houston, Lee, Russell	119 min
Jan 26, 5:35 PM CST	Mesoscale Discussion	SPC	Colbert, Fayette, Franklin, Lamar, Lauderdale, Lawrence and 5 more	55 min
Jan 26, 3:30 PM CST	Tornado Watch	SPC	Dixie, Franklin, Gadsden, Jefferson, Lafayette, Leon and 4 more	6 hr
Jan 25, 8:23 PM CST	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 16 more	97 min

Nearby

Mesoscale Discussions in Mississippi, 2012 Mesoscale Discussions in Alabama, 2012 Mesoscale Discussions in Florida, 2012 Every 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.