Alert archive / Georgia / Mesoscale Discussions in 2011

Mesoscale Discussion 507

April 21, 2011Duval County, Nassau County, Florida; 28 counties in Georgia; 11 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Apr 21, 2011, 5:40 PM EDT for Duval County, Nassau County, Florida; 28 counties in Georgia; 11 counties in South Carolina. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued
Apr 21, 2011, 5:40 PM EDT (21:40 UTC)
Expired
Apr 21, 2011, 8:15 PM EDT
In force
3 hr
Issued by
the Storm Prediction Center
All 41 counties

Duval County, FL, Nassau County, FL, Appling County, GA, Bacon County, GA, Brantley County, GA, Bryan County, GA, Bulloch County, GA, Burke County, GA, Camden County, GA, Candler County, GA, Charlton County, GA, Chatham County, GA, Effingham County, GA, Emanuel County, GA, Evans County, GA, Glynn County, GA, Jeff Davis County, GA, Jenkins County, GA, Liberty County, GA, Long County, GA, McIntosh County, GA, Montgomery County, GA, Pierce County, GA, Screven County, GA, Tattnall County, GA, Toombs County, GA, Treutlen County, GA, Ware County, GA, Wayne County, GA, Wheeler County, GA, Allendale County, SC, Bamberg County, SC, Barnwell County, SC, Beaufort County, SC, Berkeley County, SC, Charleston County, SC, Colleton County, SC, Dorchester County, SC, Georgetown County, SC, Hampton County, SC, Jasper County, SC

The radar

The Charleston,SC radar (KCLX), 72 km from the middle of the area, began a volume at 21:41 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 nearest sounding before it

Charleston AFB, SC (KCHS), launched 12:00Z, 9.7 hours before the alert went out and 140 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, Charleston AFB, SC at 12:00Z on 2011-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1320 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, Charleston AFB, SC at 12:00Z on 2011-04-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 73 square meters per square second.1939Sfc1 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
1320 J/kg
Mixed-layer CIN
-65 J/kg
Mixed-layer LCL
1241 m above ground
0-6 km bulk shear
13 kt
0-1 km storm-relative helicity
73 m²/s²
0-3 km storm-relative helicity
68 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.

IssuedProductOfficeCountiesLasted
Apr 21, 2:05 AM EDTMesoscale DiscussionSPCBaldwin, Barrow, Bartow, Bibb, Butts, Carroll and 39 more85 min
Apr 21, 2:32 AM EDTSevere Thunderstorm WatchSPCBaldwin, Banks, Barrow, Bartow, Butts, Carroll and 51 more2 hr
Apr 21, 4:09 AM EDTMesoscale DiscussionSPCClarke, Elbert, Franklin, Greene, Hart, Lincoln and 5 more96 min

Nearby

Mesoscale Discussions in Georgia, 2011Mesoscale Discussions in South Carolina, 2011Mesoscale Discussions in Florida, 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.