Alert archive / South Carolina / Mesoscale Discussions in 2009

Mesoscale Discussion 2145

October 27, 2009Chatham County, Effingham County, Georgia; 12 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Oct 27, 2009, 6:56 PM EDT for Chatham County, Effingham County, Georgia; 12 counties in South Carolina. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued: Oct 27, 2009, 6:56 PM EDT (22:56 UTC)
Expired: Oct 27, 2009, 8:30 PM EDT
In force: 94 min
Issued by: the Storm Prediction Center

Counties Chatham County, GA, Effingham County, GA, Allendale County, SC, Bamberg County, SC, Barnwell County, SC, Beaufort County, SC, Berkeley County, SC, Charleston County, SC, Clarendon County, SC, Colleton County, SC, Dorchester County, SC, Hampton County, SC, Jasper County, SC, Orangeburg County, SC

The radar

The Charleston,SC radar (KCLX), 58 km from the middle of the area, began a volume at 22:59 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 777Oct 27, 7:10 PM EDT

The nearest sounding before it

Charleston AFB, SC (KCHS), launched 12:00Z, 10.9 hours before the alert went out and 69 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 413 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 169 m²/s²
0-3 km storm-relative helicity: 176 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.5

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
Oct 27, 8:32 AM EDT	Mesoscale Discussion	SPC	Brooks, Decatur, Grady, Seminole, Thomas	88 min
Oct 27, 9:14 AM EDT	Tornado Watch	SPC	Berrien, Brooks, Colquitt, Cook, Decatur, Grady and 6 more	8 hr
Oct 27, 11:24 AM EDT	Mesoscale Discussion	SPC	Decatur, Grady, Seminole, Thomas	2 hr
Oct 27, 2:57 PM EDT	Mesoscale Discussion	SPC	Brooks, Grady, Lanier, Lowndes, Thomas	2 hr
Oct 27, 3:43 PM EDT	Mesoscale Discussion	SPC	Bryan, Chatham, Liberty	2 hr
Oct 27, 4:43 PM EDT	Mesoscale Discussion	SPC	Atkinson, Brantley, Brooks, Camden, Charlton, Clinch and 7 more	92 min
Oct 27, 7:08 PM EDT	Tornado Watch	SPC	Bryan, Chatham, Effingham	3 hr

Nearby

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