Alert archive / South Carolina / Mesoscale Discussions in 2014

Mesoscale Discussion 613

May 15, 2014Chatham County, Georgia; 19 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at May 15, 2014, 6:55 PM EDT for Chatham County, Georgia; 19 counties in South Carolina. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 15, 2014, 6:55 PM EDT (22:55 UTC)
Expired: May 15, 2014, 9:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Chatham County, GA, Beaufort County, SC, Berkeley County, SC, Calhoun County, SC, Charleston County, SC, Chesterfield County, SC, Clarendon County, SC, Colleton County, SC, Darlington County, SC, Dorchester County, SC, Florence County, SC, Georgetown County, SC, Horry County, SC, Jasper County, SC, Kershaw County, SC, Lee County, SC, Marion County, SC, Orangeburg County, SC, Sumter County, SC, Williamsburg County, SC

The radar

The Charleston,SC radar (KCLX), 75 km from the middle of the area, began a volume at 22:56 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, 10.9 hours before the alert went out and 52 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: 1386 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 609 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 146 m²/s²
0-3 km storm-relative helicity: 154 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 5.5

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

406 
ACUS11 KWNS 152255
SWOMCD
SPC MCD 152255 
SCZ000-GAZ000-160100-

MESOSCALE DISCUSSION 0613
NWS STORM PREDICTION CENTER NORMAN OK
0555 PM CDT THU MAY 15 2014

AREAS AFFECTED...PORTIONS OF ERN SC AND FAR ERN GA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 152255Z - 160100Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A LOCALIZED DMGG-WIND RISK MAY EXIST THROUGH THE
EVENING...THOUGH THE ISSUANCE OF A WW IS UNLIKELY.

DISCUSSION...MOISTURE-CHANNEL IMAGERY IMPLIES INCREASING LARGE-SCALE
FORCING FOR ASCENT IN ASSOCIATION WITH AN EMBEDDED MID-LEVEL SPEED
MAX GLANCING THE SERN ATLANTIC COASTAL STATES. A MERIDIONALLY
EXTENSIVE PLUME OF RICH TROPOSPHERIC MOISTURE PRECEDES THIS FEATURE.
GPS PW DATA SUGGEST A RIBBON OF 1.75-2.00-INCH PW EXTENDING NWD FROM
THE SWRN N ATLC INTO THE CAROLINAS...WHICH IS ASSOCIATED WITH SFC
DEWPOINTS IN THE LOWER 70S IN ADVANCE OF A N/S-ORIENTED COLD FRONT
SEGMENT ADVANCING ACROSS THE PIEDMONT. THESE FACTORS MAY FOSTER A
CONTINUED UPTICK IN CONVECTION INTO THE EVENING HOURS...WITH WATER
LOADING BEING A PRIMARY IMPETUS FOR LOCALLY DMGG WIND GUSTS.
HOWEVER...VWP DATA INDICATE MID-LEVEL FLOW BEING CONSIDERABLY WEAKER
THAN THAT ACROSS HIGHER LATITUDES -- I.E. ON THE ORDER OF 20-30 KT.
CORRESPONDING WEAKER DEEP SHEAR WILL LIKELY IMPEDE CONVECTIVE
ORGANIZATION TO LIMIT THE COVERAGE OF THE SVR-TSTM RISK. GIVEN THE
LOW-LCL ENVIRONMENT WITH AT LEAST MODEST LOW-LEVEL SHEAR...A
BRIEF/WEAK TORNADO CANNOT BE RULED OUT. HOWEVER...THIN BUOYANCY
PROFILES WILL LIMIT UPDRAFT ACCELERATIONS TO MINIMIZE SUCH
POTENTIAL...ESPECIALLY AS NOCTURNAL SFC-LAYER COOLING BECOMES
ESTABLISHED.

..COHEN/EDWARDS.. 05/15/2014

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ILM...CHS...CAE...

LAT...LON   31758129 32228118 32948107 34188075 34728041 34717991
            33967886 33057936 32078067 31758129

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 15, 12:14 AM EDT	Mesoscale Discussion	SPC	Appling, Atkinson, Bacon, Baldwin, Banks, Barrow and 51 more	91 min
May 15, 8:29 AM EDT	Mesoscale Discussion	SPC	Berkeley, Calhoun, Charleston, Chesterfield, Clarendon, Colleton and 13 more	2 hr

Nearby

Mesoscale Discussions in South Carolina, 2014 Mesoscale Discussions in Georgia, 2014 Every mesoscale discussion in 2014

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.