Alert archive / Alabama / Mesoscale Discussions in 2009

Mesoscale Discussion 694

May 4, 20094 states

The Storm Prediction Center issued this mesoscale discussion at May 4, 2009, 4:58 AM CDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 4, 2009, 4:58 AM CDT (09:58 UTC)
Expired: May 4, 2009, 7:00 AM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 37 counties

Baldwin County, AL, Barbour County, AL, Butler County, AL, Clarke County, AL, Coffee County, AL, Conecuh County, AL, Covington County, AL, Crenshaw County, AL, Dale County, AL, Escambia County, AL, Geneva County, AL, Houston County, AL, Mobile County, AL, Monroe County, AL, Pike County, AL, Washington County, AL, Escambia County, FL, Holmes County, FL, Okaloosa County, FL, Santa Rosa County, FL, Walton County, FL, East Baton Rouge Parish, LA, Livingston Parish, LA, Saint Helena Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Lamar County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS

The radar

The Mobile radar (KMOB), 29 km from the middle of the area, began a volume at 10:00 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 238May 4, 7:35 AM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 10.0 hours before the alert went out and 172 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: 332 J/kg
Mixed-layer CIN: -105 J/kg
Mixed-layer LCL: 1021 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 25 m²/s²
0-3 km storm-relative helicity: 169 m²/s²
Significant tornado parameter: -0.1
Supercell composite: -1.0

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 4, 1:30 AM CDT	Mesoscale Discussion	SPC	Barbour, Bullock, Butler, Choctaw, Clarke, Coffee and 13 more	3 hr
May 4, 2:12 AM CDT	Mesoscale Discussion	SPC	Baldwin, Coffee, Covington, Dale, Escambia, Geneva and 2 more	93 min
May 4, 2:34 AM CDT	Tornado Watch	SPC	Baldwin, Butler, Clarke, Conecuh, Covington, Crenshaw and 5 more	5 hr
May 4, 7:33 AM CDT	Tornado Watch	SPC	Baldwin, Butler, Coffee, Conecuh, Covington, Crenshaw and 6 more	6 hr
May 4, 10:38 AM CDT	Mesoscale Discussion	SPC	Barbour, Dale, Geneva, Henry, Houston	67 min
May 4, 1:34 PM CDT	Mesoscale Discussion	SPC	Baldwin, Coffee, Conecuh, Covington, Dale, Escambia and 2 more	56 min
May 4, 3:24 PM CDT	Mesoscale Discussion	SPC	Bibb, Chilton, Choctaw, Clarke, Clay, Coosa and 7 more	66 min
May 4, 12:02 PM CDT	Severe Thunderstorm Watch	SPC	Baker, Columbia, Gadsden, Hamilton, Jefferson, Leon and 4 more	7 hr

Nearby

Mesoscale Discussions in Alabama, 2009 Mesoscale Discussions in Mississippi, 2009 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; radar from the NEXRAD Level II archive.