Alert archive / Louisiana / Mesoscale Discussions in 2018

Mesoscale Discussion 1636

November 12, 201815 parishes in Louisiana; Hancock County, Harrison County, Jackson County, Mississippi

The Storm Prediction Center issued this mesoscale discussion at Nov 12, 2018, 4:01 AM CST for 15 parishes in Louisiana; Hancock County, Harrison County, Jackson County, Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Nov 12, 2018, 4:01 AM CST (10:01 UTC)
Expired: Nov 12, 2018, 6:30 AM CST
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 60%

Counties Ascension Parish, LA, Assumption Parish, LA, Iberia Parish, LA, 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, St. Mary Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Hancock County, MS, Harrison County, MS, Jackson County, MS

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 426Nov 12, 4:35 AM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 10.0 hours before the alert went out and 74 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1807 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 66 m²/s²
0-3 km storm-relative helicity: 174 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.

Issued	Product	Office	Counties	Lasted
Nov 12, 4:34 AM CST	Tornado Watch	SPC	Assumption, Cameron, Iberia, Jefferson, Lafourche, Orleans and 10 more	7 hr
Nov 12, 7:54 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Iberia, Jefferson, Lafourche, Orleans and 9 more	2 hr
Nov 12, 11:25 AM CST	Mesoscale Discussion	SPC	Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 2 more	95 min
Nov 12, 11:46 AM CST	Tornado Watch	SPC	Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 3 more	7 hr

Nearby

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