Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 1690

August 3, 201214 counties in Alabama; 27 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Aug 3, 2012, 11:56 AM CDT for 14 counties in Alabama; 27 counties in Mississippi. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued: Aug 3, 2012, 11:56 AM CDT (16:56 UTC)
Expired: Aug 3, 2012, 1:00 PM CDT
In force: 64 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 41 counties

Bibb County, AL, Choctaw County, AL, Dallas County, AL, Fayette County, AL, Greene County, AL, Hale County, AL, Lamar County, AL, Marengo County, AL, Perry County, AL, Pickens County, AL, Sumter County, AL, Tuscaloosa County, AL, Walker County, AL, Wilcox County, AL, Attala County, MS, Carroll County, MS, Choctaw County, MS, Clarke County, MS, Clay County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Jasper County, MS, Kemper County, MS, Lauderdale County, MS, Leake County, MS, Leflore County, MS, Lowndes County, MS, Madison County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Webster County, MS, Winston County, MS, Yazoo County, MS

The radar

The Columbus AFB radar (KGWX), 124 km from the middle of the area, began a volume at 16:58 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.

Severe Thunderstorm Watch 552Aug 3, 12:15 PM CDT

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 4.9 hours before the alert went out and 136 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: 2849 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 681 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: -19 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.9

Open this sounding in Storm Lab

The text

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

623 
ACUS11 KWNS 031657
SWOMCD
SPC MCD 031656
ALZ000-MSZ000-031800-

MESOSCALE DISCUSSION 1690
NWS STORM PREDICTION CENTER NORMAN OK
1156 AM CDT FRI AUG 03 2012

AREAS AFFECTED...CENTRAL PARTS OF MS/AL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 031656Z - 031800Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE ACROSS CENTRAL
MS INTO CENTRAL AL THIS AFTERNOON WITH THE POTENTIAL FOR A SEVERE
WEATHER THREAT.  WW ISSUANCE IS BEING CONSIDERED FOR THIS AFTERNOON.

DISCUSSION...VISIBLE SATELLITE IMAGERY SHOWED AN INCREASE CU
DEVELOPMENT FROM NORTH CENTRAL MS /JUST S OF THE CLOUD SHIELD/ SEWD
INTO WEST CENTRAL AND SRN AL...AND SERN MS.  THIS CORRIDOR OF DEEP
CU FORMATION WITH A FEW TSTMS ALREADY DEVELOPING PER REGIONAL RADAR
IMAGERY AND LIGHTNING DATA.  THIS ACTIVITY IS LOCATED ALONG A SUBTLE
SURFACE TROUGH WITH FORCING FOR ASCENT ATTENDANT TO A SSEWD MOVING
MCV OVER NWRN AL AND LOWER TROPOSPHERIC WEAK WAA S OF THIS FEATURE
WILL SUPPORT ADDITIONAL TSTM DEVELOPMENT THIS AFTERNOON.  MODIFIED
12Z JAN RAOB SUGGESTED SURFACE TEMPERATURES RISING INTO THE UPPER
80S WOULD BE SUFFICIENT TO WEAKEN INHIBITION...AND THESE TRENDS ARE
NOW BEING OBSERVED PER TSTM DEVELOPMENT AND TRENDS IN OBJECTIVE
ANALYSES.  EFFECTIVE BULK SHEAR OF 25-30 KT SAMPLED BY THE VWP/S AT
NQA AND GWX SUGGEST MULTICELLS WILL THE DOMINANT STORM MODE WITH AN
ATTENDANT THREAT FOR DAMAGING WINDS AND HAIL.

..PETERS/THOMPSON.. 08/03/2012

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

ATTN...WFO...BMX...MOB...MEG...JAN...

LAT...LON   33569041 33918981 33828822 33828725 33468681 32778692
            32018717 31788731 31708843 31738888 31899000 32599052
            33309070 33569041

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 3, 12:14 PM CDT	Severe Thunderstorm Watch	SPC	Autauga, Bibb, Chilton, Coosa, Dallas, Elmore and 11 more	6 hr
Aug 3, 3:33 PM CDT	Mesoscale Discussion	SPC	Autauga, Bibb, Chilton, Coosa, Dallas, Elmore and 12 more	57 min

Nearby

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