Alert archive / Louisiana / Mesoscale Discussions in 2015

Mesoscale Discussion 2091

December 27, 201510 counties in Arkansas; 16 parishes in Louisiana; 9 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 27, 2015, 7:11 PM CST for 10 counties in Arkansas; 16 parishes in Louisiana; 9 counties in Texas. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued: Dec 27, 2015, 7:11 PM CST (01:11 UTC)
Expired: Dec 27, 2015, 8:45 PM CST
In force: 94 min
Issued by: the Storm Prediction Center

All 35 counties

Ashley County, AR, Bradley County, AR, Calhoun County, AR, Columbia County, AR, Drew County, AR, Lafayette County, AR, Miller County, AR, Nevada County, AR, Ouachita County, AR, Union County, AR, Allen Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Jackson Parish, LA, Lincoln Parish, LA, Natchitoches Parish, LA, Red River Parish, LA, Sabine Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, Winn Parish, LA, Harrison County, TX, Jasper County, TX, Marion County, TX, Newton County, TX, Panola County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Tyler County, TX

The radar

The Shreveport radar (KSHV), 63 km from the middle of the area, began a volume at 01:12 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 573Dec 27, 9:55 PM CST

The nearest sounding before it

Shreveport, LA (KBAD), launched 00:00Z, 1.2 hours before the alert went out and 61 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: 692 J/kg
Mixed-layer CIN: -10 J/kg
Mixed-layer LCL: 1047 m above ground
0-6 km bulk shear: 61 kt
0-1 km storm-relative helicity: 360 m²/s²
0-3 km storm-relative helicity: 462 m²/s²
Significant tornado parameter: 1.9
Supercell composite: 9.3

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
Dec 27, 8:59 PM CST	Mesoscale Discussion	SPC	Ashley, Chicot, Union	91 min
Dec 27, 9:57 PM CST	Tornado Watch	SPC	Ashley, Chicot, Columbia, Union	7 hr
Dec 27, 11:49 PM CST	Mesoscale Discussion	SPC	Ashley, Chicot, Union	86 min
Dec 28, 2:03 AM CST	Mesoscale Discussion	SPC	Arkansas, Ashley, Bradley, Chicot, Desha, Drew and 1 more	117 min
Dec 28, 2:23 AM CST	Tornado Watch	SPC	Lee, Phillips	8 hr
Dec 28, 5:14 AM CST	Mesoscale Discussion	SPC	Crittenden, Cross, Lee, Mississippi, Monroe, Phillips and 3 more	2 hr
Dec 27, 10:41 PM CST	Mesoscale Discussion	SPC	Archer, Armstrong, Baylor, Borden, Briscoe, Brown and 56 more	4 hr
Dec 28, 2:41 AM CST	Mesoscale Discussion	SPC	Wichita	6 hr

Nearby

Mesoscale Discussions in Louisiana, 2015 Mesoscale Discussions in Arkansas, 2015 Mesoscale Discussions in Texas, 2015 Every mesoscale discussion in 2015

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.