Alert archive / Louisiana / Mesoscale Discussions in 2018

Mesoscale Discussion 83

February 21, 201826 parishes in Louisiana; 6 counties in Mississippi; Newton County, Orange County, Texas

The Storm Prediction Center issued this mesoscale discussion at Feb 21, 2018, 3:03 PM CST for 26 parishes in Louisiana; 6 counties in Mississippi; Newton County, Orange County, Texas. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued: Feb 21, 2018, 3:03 PM CST (21:03 UTC)
Expired: Feb 21, 2018, 5:00 PM CST
In force: 117 min
Issued by: the Storm Prediction Center

All 34 counties

Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Richland Parish, LA, Saint Landry Parish, LA, Tensas Parish, LA, Vernon Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Claiborne County, MS, Franklin County, MS, Jefferson County, MS, Warren County, MS, Wilkinson County, MS, Newton County, TX, Orange County, TX

The radar

The Ft Polk radar (KPOE), 65 km from the middle of the area, began a volume at 21:02 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

Shreveport, LA (KBAD), launched 12:00Z, 9.1 hours before the alert went out and 159 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: 1043 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 529 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 151 m²/s²
0-3 km storm-relative helicity: 175 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 4.1

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
Feb 21, 9:07 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Caldwell and 12 more	113 min
Feb 21, 9:48 AM CST	Tornado Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Caldwell and 17 more	7 hr
Feb 21, 12:28 PM CST	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Caldwell and 17 more	92 min
Feb 21, 7:57 AM CST	Mesoscale Discussion	SPC	Archer, Baylor, Borden, Callahan, Childress, Clay and 35 more	4 hr
Feb 21, 12:44 PM CST	Mesoscale Discussion	SPC	Clay, Cooke, Denton, Jack, Montague, Palo Pinto and 1 more	4 hr

Nearby

Mesoscale Discussions in Louisiana, 2018 Mesoscale Discussions in Mississippi, 2018 Mesoscale Discussions in Texas, 2018 Every mesoscale discussion in 2018

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.