Alert archive / Louisiana / Mesoscale Discussions in 2011

Mesoscale Discussion 837

May 21, 2011Ashley County, Columbia County, Union County, Arkansas; 16 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at May 21, 2011, 3:38 PM CDT for Ashley County, Columbia County, Union County, Arkansas; 16 parishes in Louisiana. It was in force for 97 min.

The area

The outline as issued.

The facts

Issued
May 21, 2011, 3:38 PM CDT (20:38 UTC)
Expired
May 21, 2011, 5:15 PM CDT
In force
97 min
Issued by
the Storm Prediction Center

Counties Ashley County, AR, Columbia County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Franklin Parish, LA, Jackson Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Ouachita Parish, LA, Richland Parish, LA, Tensas Parish, LA, Union Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA

The radar

The Shreveport radar (KSHV), 133 km from the middle of the area, began a volume at 20:37 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 (KSHV), launched 12:00Z, 8.6 hours before the alert went out and 124 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-pSkew-T log-p diagram, Shreveport, LA at 12:00Z on 2011-05-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Shreveport, LA at 12:00Z on 2011-05-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 218 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
1 J/kg
Mixed-layer CIN
-398 J/kg
Mixed-layer LCL
813 m above ground
0-6 km bulk shear
50 kt
0-1 km storm-relative helicity
218 m²/s²
0-3 km storm-relative helicity
238 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0

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.

IssuedProductOfficeCountiesLasted
May 20, 9:06 PM CDTMesoscale DiscussionSPCClark, Columbia, Dallas, Garland, Grant, Hempstead and 8 more114 min

Nearby

Mesoscale Discussions in Louisiana, 2011Mesoscale Discussions in Arkansas, 2011Every mesoscale discussion in 2011

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.