Alert archive / Mississippi / Mesoscale Discussions in 2008

Mesoscale Discussion 660

April 18, 200814 parishes in Louisiana; 19 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2008, 3:24 PM CDT for 14 parishes in Louisiana; 19 counties in Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 18, 2008, 3:24 PM CDT (20:24 UTC)
Expired: Apr 18, 2008, 5:30 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 33 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Hinds County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Pike County, MS, Rankin County, MS, Simpson County, MS, Smith County, MS, Walthall County, MS, Wilkinson County, MS

The watches that followed

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

Tornado Watch 207Apr 18, 3:45 PM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 8.4 hours before the alert went out and 83 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: 36 J/kg
Mixed-layer CIN: -35 J/kg
Mixed-layer LCL: 623 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 225 m²/s²
0-3 km storm-relative helicity: 290 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
Apr 18, 3:43 PM CDT	Tornado Watch	SPC	Ascension, Assumption, Jefferson, Lafourche, Livingston, Orleans and 10 more	7 hr
Apr 18, 6:07 PM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, Jefferson, Lafourche, Livingston, Orleans and 10 more	53 min
Apr 18, 3:07 PM CDT	Mesoscale Discussion	SPC	Benton, DeSoto, Marshall, Tate, Tunica	113 min
Apr 18, 5:08 PM CDT	Mesoscale Discussion	SPC	Alcorn, Attala, Benton, Calhoun, Chickasaw, Choctaw and 16 more	37 min

Nearby

Mesoscale Discussions in Mississippi, 2008 Mesoscale Discussions in Louisiana, 2008 Every mesoscale discussion in 2008

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.