Alert archive / Alabama / Mesoscale Discussions in 2017

Mesoscale Discussion 1605

August 31, 201711 counties in Alabama; 9 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2017, 10:31 AM CDT for 11 counties in Alabama; 9 counties in Mississippi. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Aug 31, 2017, 10:31 AM CDT (15:31 UTC)
Expired: Aug 31, 2017, 12:30 PM CDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

Counties Choctaw County, AL, Fayette County, AL, Greene County, AL, Hale County, AL, Lamar County, AL, Marion County, AL, Mobile County, AL, Pickens County, AL, Sumter County, AL, Tuscaloosa County, AL, Washington County, AL, George County, MS, Itawamba County, MS, Jackson County, MS, Lee County, MS, Lowndes County, MS, Monroe County, MS, Noxubee County, MS, Prentiss County, MS, Tishomingo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 155 km from the middle of the area, began a volume at 15:34 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 476Aug 31, 11:15 AM CDT

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 3.5 hours before the alert went out and 180 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: 724 J/kg
Mixed-layer CIN: -9 J/kg
Mixed-layer LCL: 569 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 198 m²/s²
0-3 km storm-relative helicity: 229 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 4.5

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 31, 11:13 AM CDT	Tornado Watch	SPC	Bibb, Blount, Chilton, Colbert, Coosa, Cullman and 22 more	11 hr
Aug 31, 2:35 PM CDT	Mesoscale Discussion	SPC	Colbert, Fayette, Franklin, Greene, Lamar, Marion and 3 more	115 min
Aug 31, 5:47 PM CDT	Mesoscale Discussion	SPC	Bibb, Chilton, Colbert, Cullman, Fayette, Franklin and 16 more	88 min

Nearby

Mesoscale Discussions in Alabama, 2017 Mesoscale Discussions in Mississippi, 2017 Every mesoscale discussion in 2017

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.