Alert archive / Louisiana / Mesoscale Discussions in 2018

Mesoscale Discussion 1732

December 27, 20187 counties in Arkansas; 8 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Dec 27, 2018, 1:39 AM CST for 7 counties in Arkansas; 8 parishes in Louisiana. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Dec 27, 2018, 1:39 AM CST (07:39 UTC)
Expired
Dec 27, 2018, 3:45 AM CST
In force
2 hr
Issued by
the Storm Prediction Center

Counties Calhoun County, AR, Columbia County, AR, Hempstead County, AR, Lafayette County, AR, Nevada County, AR, Ouachita County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Lincoln Parish, LA, Red River Parish, LA, Webster Parish, LA

The radar

The Shreveport radar (KSHV), 73 km from the middle of the area, began a volume at 07:38 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 00:00Z, 7.7 hours before the alert went out and 65 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 00:00Z on 2018-12-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 00:00Z on 2018-12-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 280 square meters per square second.1939587897Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
836 m above ground
0-6 km bulk shear
51 kt
0-1 km storm-relative helicity
280 m²/s²
0-3 km storm-relative helicity
510 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.

IssuedProductOfficeCountiesLasted
Dec 27, 12:02 AM CSTSevere Thunderstorm WatchSPCColumbia, Hempstead, Howard, Lafayette, Little River, Miller and 2 more5 hr
Dec 26, 11:40 PM CSTMesoscale DiscussionSPCBossier, Caddo, De Soto2 hr
Dec 27, 3:09 AM CSTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Cameron, Jefferson Davis, Vernon2 hr
Dec 27, 3:43 AM CSTTornado WatchSPCAcadia, Allen, Beauregard, Calcasieu, Caldwell, Cameron and 10 more10 hr
Dec 27, 7:12 AM CSTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 11 more2 hr
Dec 27, 9:00 AM CSTMesoscale DiscussionSPCAvoyelles, Catahoula, Concordia, East Baton Rouge, East Feliciana, Iberville and 6 more60 min
Dec 27, 9:29 AM CSTTornado WatchSPCAscension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 27 more9 hr
Dec 27, 1:50 PM CSTMesoscale DiscussionSPCAscension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 19 more85 min

Nearby

Mesoscale Discussions in Louisiana, 2018Mesoscale Discussions in Arkansas, 2018Every 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.