Alert archive / Louisiana / Mesoscale Discussions in 2019

Mesoscale Discussion 673

May 18, 201917 parishes in Louisiana; 15 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at May 18, 2019, 5:16 PM CDT for 17 parishes in Louisiana; 15 counties in Texas. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: May 18, 2019, 5:16 PM CDT (22:16 UTC)
Expired: May 18, 2019, 7:15 PM CDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 32 counties

Bienville Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Sabine Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, Winn Parish, LA, Angelina County, TX, Grimes County, TX, Houston County, TX, Jasper County, TX, Nacogdoches County, TX, Newton County, TX, Panola County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX

The radar

The Ft Polk radar (KPOE), 87 km from the middle of the area, began a volume at 22:18 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 189May 18, 7:00 PM CDT

The nearest sounding before it

Shreveport, LA (KBAD), launched 12:00Z, 10.3 hours before the alert went out and 94 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: 471 J/kg
Mixed-layer CIN: -216 J/kg
Mixed-layer LCL: 727 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: -16 m²/s²
0-3 km storm-relative helicity: 98 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

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
May 18, 12:48 PM CDT	Tornado Watch	SPC	Bossier, Caddo	7 hr
May 17, 9:20 PM CDT	Mesoscale Discussion	SPC	Crockett, Irion, Reagan, Schleicher, Sutton, Terrell and 1 more	85 min
May 17, 11:47 PM CDT	Mesoscale Discussion	SPC	Borden, Brown, Callahan, Coke, Coleman, Concho and 34 more	2 hr
May 18, 1:35 AM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Borden, Brown, Callahan, Clay and 33 more	2 hr
May 18, 2:20 AM CDT	Tornado Watch	SPC	Archer, Baylor, Borden, Brown, Callahan, Childress and 54 more	8 hr
May 18, 5:11 AM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Brown, Callahan, Clay, Coke and 34 more	2 hr
May 18, 6:51 AM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Brown, Callahan, Clay, Coke and 26 more	114 min
May 18, 9:10 AM CDT	Tornado Watch	SPC	Bosque, Brown, Coleman, Collin, Comanche, Concho and 36 more	8 hr
May 18, 12:11 PM CDT	Mesoscale Discussion	SPC	Anderson, Bell, Blanco, Bosque, Bowie, Burnet and 42 more	64 min
May 18, 1:16 PM CDT	Tornado Watch	SPC	Anderson, Bastrop, Bell, Blanco, Brazos, Burleson and 19 more	9 hr
May 18, 3:48 PM CDT	Severe Thunderstorm Watch	SPC	Lipscomb	6 hr
May 18, 6:37 PM CDT	Mesoscale Discussion	SPC	Cooke, Dallas, Denton, Parker, Tarrant, Wise	53 min

Nearby

Mesoscale Discussions in Louisiana, 2019 Mesoscale Discussions in Texas, 2019 Every mesoscale discussion in 2019

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.