Alert archive / Louisiana / Mesoscale Discussions in 2015

Mesoscale Discussion 2085

December 27, 20158 counties in Arkansas; 17 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Dec 27, 2015, 12:47 PM CST for 8 counties in Arkansas; 17 parishes in Louisiana. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued: Dec 27, 2015, 12:47 PM CST (18:47 UTC)
Expired: Dec 27, 2015, 2:15 PM CST
In force: 88 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 25 counties

Ashley County, AR, Bradley County, AR, Calhoun County, AR, Cleveland County, AR, Columbia County, AR, Drew County, AR, Ouachita County, AR, Union County, AR, Avoyelles Parish, LA, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Richland Parish, LA, Union Parish, LA, Winn Parish, LA

The radar

The Ft Polk radar (KPOE), 135 km from the middle of the area, began a volume at 18:46 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 572Dec 27, 2:40 PM CST

The nearest sounding before it

Shreveport, LA (KBAD), launched 12:00Z, 6.8 hours before the alert went out and 132 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: 625 J/kg
Mixed-layer CIN: -20 J/kg
Mixed-layer LCL: 707 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 350 m²/s²
0-3 km storm-relative helicity: 426 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 8.3

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 26, 7:32 PM CST	Mesoscale Discussion	SPC	Crawford, Sebastian	88 min
Dec 26, 11:27 PM CST	Mesoscale Discussion	SPC	Boone, Crawford, Franklin, Johnson, Logan, Madison and 8 more	2 hr
Dec 27, 5:44 AM CST	Mesoscale Discussion	SPC	Little River, Sevier	3 hr
Dec 27, 8:56 AM CST	Tornado Watch	SPC	Hempstead, Howard, Lafayette, Little River, Miller, Sevier	10 hr
Dec 27, 12:45 PM CST	Mesoscale Discussion	SPC	Hempstead, Howard, Lafayette, Little River, Miller, Sevier	2 hr
Dec 27, 2:27 PM CST	Mesoscale Discussion	SPC	Ashley, Bradley, Calhoun, Cleveland, Columbia, Dallas and 7 more	63 min
Dec 27, 2:47 PM CST	Tornado Watch	SPC	Arkansas, Ashley, Bradley, Calhoun, Clark, Cleveland and 15 more	7 hr
Dec 27, 4:55 PM CST	Mesoscale Discussion	SPC	Ashley, Bradley, Calhoun, Cleveland, Columbia, Dallas and 8 more	2 hr
Dec 27, 3:15 PM CST	Mesoscale Discussion	SPC	East Carroll, East Feliciana, Madison, Saint Helena, Tensas, Washington	90 min

Nearby

Mesoscale Discussions in Louisiana, 2015 Mesoscale Discussions in Arkansas, 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.