Alert archive / South Carolina / Mesoscale Discussions in 2012

Mesoscale Discussion 1961

September 18, 2012Effingham County, Screven County, Georgia; Union County, North Carolina; 30 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Sep 18, 2012, 11:35 AM EDT for Effingham County, Screven County, Georgia; Union County, North Carolina; 30 counties in South Carolina. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued
Sep 18, 2012, 11:35 AM EDT (15:35 UTC)
Expired
Sep 18, 2012, 1:00 PM EDT
In force
85 min
Issued by
the Storm Prediction Center
Chance of a watch
80%
All 33 counties

Effingham County, GA, Screven County, GA, Union County, NC, Aiken County, SC, Allendale County, SC, Bamberg County, SC, Barnwell County, SC, Beaufort County, SC, Berkeley County, SC, Calhoun County, SC, Charleston County, SC, Chester County, SC, Chesterfield County, SC, Clarendon County, SC, Colleton County, SC, Darlington County, SC, Dorchester County, SC, Fairfield County, SC, Florence County, SC, Georgetown County, SC, Hampton County, SC, Horry County, SC, Jasper County, SC, Kershaw County, SC, Lancaster County, SC, Lee County, SC, Lexington County, SC, Marion County, SC, Marlboro County, SC, Orangeburg County, SC, Richland County, SC, Sumter County, SC, Williamsburg County, SC

The radar

The Columbia radar (KCAE), 45 km from the middle of the area, began a volume at 15:36 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, 3.6 hours before the alert went out and 121 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 2012-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1687 joules per kilogram.LCLEL10008507005003002001001 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 2012-09-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 135 square meters per square second.19395878Sfc1 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
1687 J/kg
Mixed-layer CIN
-1 J/kg
Mixed-layer LCL
620 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
135 m²/s²
0-3 km storm-relative helicity
147 m²/s²
Significant tornado parameter
0.8
Supercell composite
5.1

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
Sep 17, 8:14 PM EDTMesoscale DiscussionSPCBaldwin, Banks, Barrow, Bartow, Bibb, Bleckley and 85 more2 hr
Sep 17, 10:21 PM EDTMesoscale DiscussionSPCBaldwin, Banks, Barrow, Clarke, Elbert, Franklin and 21 more84 min
Sep 18, 12:23 AM EDTMesoscale DiscussionSPCBurke, Candler, Columbia, Elbert, Emanuel, Glascock and 17 more97 min
Sep 18, 3:44 AM EDTMesoscale DiscussionSPCBaker, Calhoun, Clay, Decatur, Dougherty, Early and 7 more2 hr
Sep 18, 9:39 AM EDTMesoscale DiscussionSPCAppling, Atkinson, Bacon, Ben Hill, Berrien, Brantley and 39 more66 min
Sep 18, 8:49 AM EDTMesoscale DiscussionSPCAlamance, Anson, Caswell, Chatham, Cumberland, Davidson and 31 more116 min
Sep 18, 9:45 AM EDTTornado WatchSPCAlamance, Anson, Chatham, Cumberland, Davidson, Durham and 25 more8 hr
Sep 18, 10:54 AM EDTTornado WatchSPCBertie, Camden, Caswell, Chowan, Currituck, Gates and 4 more9 hr
Sep 18, 11:19 AM EDTMesoscale DiscussionSPCAlamance, Caswell, Chatham, Cumberland, Durham, Edgecombe and 27 more86 min
Sep 18, 1:00 PM EDTTornado WatchSPCBeaufort, Carteret, Craven, Dare, Duplin, Greene and 9 more5 hr
Sep 18, 1:21 PM EDTMesoscale DiscussionSPCAlamance, Anson, Chatham, Cumberland, Davidson, Durham and 25 more84 min
Sep 18, 1:27 PM EDTMesoscale DiscussionSPCCamden, Chowan, Currituck, Gates, Hertford, Northampton and 2 more63 min
Sep 18, 3:52 PM EDTMesoscale DiscussionSPCBertie, Camden, Chowan, Gates, Hertford, Northampton and 2 more113 min
Sep 18, 4:11 PM EDTMesoscale DiscussionSPCAlamance, Anson, Beaufort, Carteret, Chatham, Craven and 40 more94 min
Sep 18, 6:15 PM EDTMesoscale DiscussionSPCCamden, Carteret, Chowan, Currituck, Dare, Gates and 5 more30 min

Nearby

Mesoscale Discussions in South Carolina, 2012Mesoscale Discussions in Georgia, 2012Mesoscale Discussions in North Carolina, 2012Every 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.