Alert archive / Louisiana / Mesoscale Discussions in 2009

Mesoscale Discussion 798

May 11, 20098 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at May 11, 2009, 6:15 PM CDT for 8 parishes in Louisiana. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: May 11, 2009, 6:15 PM CDT (23:15 UTC)
Expired: May 11, 2009, 7:45 PM CDT
In force: 90 min
Issued by: the Storm Prediction Center

Counties Ascension Parish, LA, Assumption Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 11.3 hours before the alert went out and 266 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: 339 J/kg
Mixed-layer CIN: -90 J/kg
Mixed-layer LCL: 611 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 57 m²/s²
0-3 km storm-relative helicity: 106 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.

Issued	Product	Office	Counties	Lasted
May 10, 7:29 PM CDT	Mesoscale Discussion	SPC	Concordia, Grant	61 min
May 10, 7:50 PM CDT	Severe Thunderstorm Watch	SPC	Catahoula, Concordia, Tensas	5 hr
May 11, 1:05 PM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 11 more	85 min
May 11, 2:20 PM CDT	Mesoscale Discussion	SPC	Allen, Avoyelles, Catahoula, Concordia, East Baton Rouge, East Feliciana and 13 more	55 min
May 11, 2:52 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 21 more	5 hr

Nearby

Mesoscale Discussions in Louisiana, 2009 Every mesoscale discussion in 2009

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.