Alert archive / Louisiana / Mesoscale Discussions in 2011

Mesoscale Discussion 2105

September 3, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Sep 3, 2011, 7:46 AM CDT for 4 states. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Sep 3, 2011, 7:46 AM CDT (12:46 UTC)
Expired: Sep 3, 2011, 9:45 AM CDT
In force: 119 min
Issued by: the Storm Prediction Center

Counties Baldwin County, AL, Escambia County, AL, Mobile County, AL, Escambia County, FL, Santa Rosa County, FL, Jefferson Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, George County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Stone County, MS

The radar

The Mobile radar (KMOB), 113 km from the middle of the area, began a volume at 12:47 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 828Sep 3, 9:40 AM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 0.8 hours before the alert went out and 75 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: 850 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 477 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 286 m²/s²
0-3 km storm-relative helicity: 260 m²/s²
Significant tornado parameter: 1.0
Supercell composite: 7.0

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
Sep 3, 1:43 AM CDT	Tornado Watch	SPC	Baldwin, Mobile	8 hr
Sep 3, 9:41 AM CDT	Tornado Watch	SPC	Baldwin, Mobile	12 hr
Sep 3, 1:41 PM CDT	Mesoscale Discussion	SPC	Baldwin, Conecuh, Covington, Escambia, Mobile, Washington	64 min
Sep 3, 5:57 PM CDT	Mesoscale Discussion	SPC	Baldwin, Escambia, Mobile, Washington	2 hr
Sep 2, 11:32 PM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 15 more	118 min

Nearby

Mesoscale Discussions in Louisiana, 2011 Mesoscale Discussions in Mississippi, 2011 Mesoscale Discussions in Alabama, 2011 Every 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.