Alert archive / Georgia / Mesoscale Discussions in 2009

Mesoscale Discussion 534

April 20, 200910 counties in Georgia; 8 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2009, 12:20 AM EDT for 10 counties in Georgia; 8 counties in South Carolina. It was in force for 55 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2009, 12:20 AM EDT (04:20 UTC)
Expired: Apr 20, 2009, 1:15 AM EDT
In force: 55 min
Issued by: the Storm Prediction Center

Counties Elbert County, GA, Franklin County, GA, Greene County, GA, Hart County, GA, Lincoln County, GA, Madison County, GA, McDuffie County, GA, Oglethorpe County, GA, Taliaferro County, GA, Wilkes County, GA, Abbeville County, SC, Anderson County, SC, Greenville County, SC, Greenwood County, SC, Laurens County, SC, McCormick County, SC, Oconee County, SC, Pickens County, SC

The radar

The Greer radar (KGSP), 80 km from the middle of the area, began a volume at 04:21 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 177Apr 20, 12:45 AM EDT

The nearest sounding before it

Peachtre/Fal Fld, GA (KFFC), launched 00:00Z, 4.3 hours before the alert went out and 193 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: 182 J/kg
Mixed-layer CIN: -11 J/kg
Mixed-layer LCL: 1004 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 212 m²/s²
0-3 km storm-relative helicity: 248 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
Apr 19, 8:51 PM EDT	Tornado Watch	SPC	Barrow, Bartow, Butts, Carroll, Catoosa, Chattooga and 42 more	6 hr
Apr 19, 11:21 PM EDT	Mesoscale Discussion	SPC	Barrow, Bartow, Butts, Carroll, Chattooga, Cherokee and 35 more	84 min
Apr 20, 12:42 AM EDT	Tornado Watch	SPC	Baldwin, Banks, Clarke, Columbia, Elbert, Franklin and 19 more	5 hr
Apr 20, 1:22 AM EDT	Mesoscale Discussion	SPC	Barrow, Bibb, Butts, Chattahoochee, Clayton, Coweta and 26 more	53 min
Apr 20, 2:52 PM EDT	Mesoscale Discussion	SPC	Chatham	83 min
Apr 20, 3:16 PM EDT	Severe Thunderstorm Watch	SPC	Bryan, Chatham, Effingham, Liberty, Long, McIntosh	6 hr
Apr 20, 4:55 PM EDT	Mesoscale Discussion	SPC	Bryan, Bulloch, Chatham, Effingham, Evans, Liberty and 1 more	95 min
Apr 20, 7:36 PM EDT	Mesoscale Discussion	SPC	Chatham	84 min

Nearby

Mesoscale Discussions in Georgia, 2009 Mesoscale Discussions in South Carolina, 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.