Alert archive / Louisiana / Mesoscale Discussions in 2020

Mesoscale Discussion 1709

September 23, 20207 parishes in Louisiana; 4 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Sep 23, 2020, 8:45 PM CDT for 7 parishes in Louisiana; 4 counties in Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Sep 23, 2020, 8:45 PM CDT (01:45 UTC)
Expired
Sep 23, 2020, 10:45 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Concerning
Tornado watch 494

Counties Avoyelles Parish, LA, Concordia Parish, LA, East Feliciana Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Franklin County, MS, Wilkinson County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 1.8 hours before the alert went out and 196 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, Slidell Radar S, LA at 00:00Z on 2020-09-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1062 joules per kilogram.LCLEL10008507005003002001001 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, Slidell Radar S, LA at 00:00Z on 2020-09-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 222 square meters per square second.193958Sfc1 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
1062 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
497 m above ground
0-6 km bulk shear
38 kt
0-1 km storm-relative helicity
222 m²/s²
0-3 km storm-relative helicity
309 m²/s²
Significant tornado parameter
1.2
Supercell composite
6.0

Open this sounding in Storm Lab

The text

As transmitted.

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Nearby

Mesoscale Discussions in Louisiana, 2020Mesoscale Discussions in Mississippi, 2020Every mesoscale discussion in 2020

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.