Alert archive / Georgia / Mesoscale Discussions in 2012

Mesoscale Discussion 1958

September 18, 201213 counties in Florida; 45 counties in Georgia; 6 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Sep 18, 2012, 9:39 AM EDT for 13 counties in Florida; 45 counties in Georgia; 6 counties in South Carolina. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: Sep 18, 2012, 9:39 AM EDT (13:39 UTC)
Expired: Sep 18, 2012, 10:45 AM EDT
In force: 66 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 64 counties

Alachua County, FL, Baker County, FL, Bradford County, FL, Clay County, FL, Columbia County, FL, Duval County, FL, Gilchrist County, FL, Hamilton County, FL, Lafayette County, FL, Nassau County, FL, Putnam County, FL, Suwannee County, FL, Union County, FL, Appling County, GA, Atkinson County, GA, Bacon County, GA, Ben Hill County, GA, Berrien 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, Clinch County, GA, Coffee County, GA, Dodge County, GA, Echols County, GA, Effingham County, GA, Emanuel County, GA, Evans County, GA, Glascock County, GA, Glynn County, GA, Irwin County, GA, Jeff Davis County, GA, Jefferson County, GA, Jenkins County, GA, Johnson County, GA, Lanier County, GA, Laurens County, GA, Liberty County, GA, Long County, GA, Lowndes County, GA, McIntosh County, GA, Montgomery County, GA, Pierce County, GA, Richmond County, GA, Screven County, GA, Tattnall County, GA, Telfair County, GA, Toombs County, GA, Treutlen County, GA, Ware County, GA, Washington County, GA, Wayne County, GA, Wheeler County, GA, Allendale County, SC, Bamberg County, SC, Barnwell County, SC, Beaufort County, SC, Hampton County, SC, Jasper County, SC

The radar

The Charleston,SC radar (KCLX), 123 km from the middle of the area, began a volume at 13:39 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

Jacksonville, FL (KJAX), launched 12:00Z, 1.7 hours before the alert went out and 164 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: 897 J/kg
Mixed-layer CIN: -26 J/kg
Mixed-layer LCL: 697 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 75 m²/s²
0-3 km storm-relative helicity: 89 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.2

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
Sep 18, 3:44 AM EDT	Mesoscale Discussion	SPC	Bay, Calhoun, Gadsden, Holmes, Jackson, Okaloosa and 2 more	2 hr
Sep 17, 8:14 PM EDT	Mesoscale Discussion	SPC	Baldwin, Banks, Barrow, Bartow, Bibb, Bleckley and 85 more	2 hr
Sep 17, 10:21 PM EDT	Mesoscale Discussion	SPC	Baldwin, Banks, Barrow, Clarke, Elbert, Franklin and 21 more	84 min
Sep 18, 12:23 AM EDT	Mesoscale Discussion	SPC	Burke, Candler, Columbia, Elbert, Emanuel, Glascock and 17 more	97 min
Sep 18, 11:35 AM EDT	Mesoscale Discussion	SPC	Effingham, Screven	85 min
Sep 18, 11:19 AM EDT	Mesoscale Discussion	SPC	Marlboro	86 min

Nearby

Mesoscale Discussions in Georgia, 2012 Mesoscale Discussions in Florida, 2012 Mesoscale Discussions in South Carolina, 2012 Every mesoscale discussion in 2012

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.