Alert archive / Alabama / Mesoscale Discussions in 2011

Mesoscale Discussion 642

April 27, 201133 counties in Alabama; Chattooga County, Walker County, Georgia

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2011, 7:55 PM CDT for 33 counties in Alabama; Chattooga County, Walker County, Georgia. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued
Apr 27, 2011, 7:55 PM CDT (00:55 UTC)
Expired
Apr 27, 2011, 9:00 PM CDT
In force
65 min
Issued by
the Storm Prediction Center
All 35 counties

Autauga County, AL, Bibb County, AL, Blount County, AL, Butler County, AL, Calhoun County, AL, Cherokee County, AL, Chilton County, AL, Clay County, AL, Cleburne County, AL, Conecuh County, AL, Coosa County, AL, Crenshaw County, AL, Cullman County, AL, Dallas County, AL, DeKalb County, AL, Elmore County, AL, Etowah County, AL, Hale County, AL, Jefferson County, AL, Lowndes County, AL, Macon County, AL, Marengo County, AL, Marshall County, AL, Monroe County, AL, Montgomery County, AL, Perry County, AL, Randolph County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tallapoosa County, AL, Tuscaloosa County, AL, Wilcox County, AL, Chattooga County, GA, Walker County, GA

The radar

The Birmingham radar (KBMX), 43 km from the middle of the area, began a volume at 00:54 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.

The nearest sounding before it

Birmingham, AL (KBMX), launched 00:00Z, 0.9 hours before the alert went out and 43 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-pSkew-T log-p diagram, Birmingham, AL at 00:00Z on 2011-04-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3065 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Birmingham, AL at 00:00Z on 2011-04-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 448 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
3065 J/kg
Mixed-layer CIN
-4 J/kg
Mixed-layer LCL
711 m above ground
0-6 km bulk shear
73 kt
0-1 km storm-relative helicity
448 m²/s²
0-3 km storm-relative helicity
480 m²/s²
Significant tornado parameter
9.6
Supercell composite
33.6

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.

IssuedProductOfficeCountiesLasted
Apr 27, 9:20 PM CDTMesoscale DiscussionSPCAutauga, Bibb, Blount, Butler, Calhoun, Cherokee and 29 more25 min
Apr 27, 9:42 PM CDTTornado WatchSPCAutauga, Bibb, Butler, Calhoun, Cherokee, Chilton and 19 more4 hr
Apr 27, 11:09 PM CDTMesoscale DiscussionSPCBarbour, Bullock, Chambers, Clay, Cleburne, Elmore and 7 more36 min
Apr 28, 1:22 AM CDTMesoscale DiscussionSPCDale, Geneva, Henry, Houston83 min
Apr 27, 11:56 PM CDTTornado WatchSPCBaldwin, Banks, Barrow, Bibb, Bleckley, Burke and 80 more4 hr
Apr 28, 2:30 AM CDTMesoscale DiscussionSPCBaldwin, Bibb, Bleckley, Burke, Chattahoochee, Columbia and 30 more90 min
Apr 28, 3:30 AM CDTTornado WatchSPCBaldwin, Bibb, Bleckley, Bulloch, Burke, Candler and 37 more10 hr
Apr 28, 7:05 AM CDTMesoscale DiscussionSPCBurke, Candler, Dodge, Emanuel, Jefferson, Jenkins and 5 more85 min
Apr 28, 7:48 AM CDTTornado WatchSPCBryan, Bulloch, Candler, Chatham, Effingham, Evans and 6 more7 hr
Apr 28, 8:47 AM CDTSevere Thunderstorm WatchSPCAppling, Atkinson, Bacon, Brantley, Camden, Charlton and 8 more9 hr
Apr 28, 10:22 AM CDTMesoscale DiscussionSPCBulloch, Burke, Candler, Chatham, Effingham, Emanuel and 2 more53 min
Apr 28, 11:19 AM CDTMesoscale DiscussionSPCAppling, Bacon, Brantley, Camden, Charlton, Clinch and 10 more56 min

Nearby

Mesoscale Discussions in Alabama, 2011Mesoscale Discussions in Georgia, 2011Every 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.