Alert archive / Alabama / Mesoscale Discussions in 2012

Mesoscale Discussion 1878

September 3, 201223 counties in Alabama; 5 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Sep 3, 2012, 9:28 PM CDT for 23 counties in Alabama; 5 counties in Mississippi. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued: Sep 3, 2012, 9:28 PM CDT (02:28 UTC)
Expired: Sep 3, 2012, 10:30 PM CDT
In force: 62 min
Issued by: the Storm Prediction Center

All 28 counties

Autauga County, AL, Bibb County, AL, Butler County, AL, Chilton County, AL, Choctaw County, AL, Clarke County, AL, Conecuh County, AL, Crenshaw County, AL, Dallas County, AL, Elmore County, AL, Greene County, AL, Hale County, AL, Lowndes County, AL, Marengo County, AL, Monroe County, AL, Montgomery County, AL, Perry County, AL, Pickens County, AL, Pike County, AL, Sumter County, AL, Tuscaloosa County, AL, Washington County, AL, Wilcox County, AL, Clay County, MS, Lowndes County, MS, Noxubee County, MS, Oktibbeha County, MS, Winston County, MS

The radar

The Birmingham radar (KBMX), 81 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

Birmingham, AL (KBMX), launched 00:00Z, 2.5 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: 1069 J/kg
Mixed-layer CIN: -48 J/kg
Mixed-layer LCL: 747 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 124 m²/s²
0-3 km storm-relative helicity: 238 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 3.9

Open this sounding in Storm Lab

The text

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

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 4, 3:42 PM CDT	Mesoscale Discussion	SPC	Autauga, Butler, Choctaw, Clarke, Conecuh, Crenshaw and 13 more	63 min

Nearby

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