Alert archive / North Carolina / Mesoscale Discussions in 2012

Mesoscale Discussion 877

May 23, 201237 counties in North Carolina; 18 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at May 23, 2012, 1:15 PM EDT for 37 counties in North Carolina; 18 counties in South Carolina. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: May 23, 2012, 1:15 PM EDT (17:15 UTC)
Expired: May 23, 2012, 2:15 PM EDT
In force: 60 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 55 counties

Beaufort County, NC, Bertie County, NC, Bladen County, NC, Chatham County, NC, Chowan County, NC, Columbus County, NC, Craven County, NC, Cumberland County, NC, Duplin County, NC, Durham County, NC, Edgecombe County, NC, Franklin County, NC, Granville County, NC, Greene County, NC, Halifax County, NC, Harnett County, NC, Hoke County, NC, Johnston County, NC, Jones County, NC, Lee County, NC, Lenoir County, NC, Martin County, NC, Moore County, NC, Nash County, NC, Onslow County, NC, Orange County, NC, Pender County, NC, Pitt County, NC, Richmond County, NC, Robeson County, NC, Sampson County, NC, Scotland County, NC, Vance County, NC, Wake County, NC, Washington County, NC, Wayne County, NC, Wilson County, NC, Berkeley County, SC, Calhoun County, SC, Chesterfield County, SC, Clarendon County, SC, Darlington County, SC, Dillon County, SC, Dorchester County, SC, Florence County, SC, Georgetown County, SC, Horry County, SC, Kershaw County, SC, Lee County, SC, Marion County, SC, Marlboro County, SC, Orangeburg County, SC, Richland County, SC, Sumter County, SC, Williamsburg County, SC

The radar

The Wilmington radar (KLTX), 84 km from the middle of the area, began a volume at 17:19 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.

Severe Thunderstorm Watch 292May 23, 1:45 PM EDT

The nearest sounding before it

Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 5.3 hours before the alert went out and 192 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: 63 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 574 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: 40 m²/s²
0-3 km storm-relative helicity: 35 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

901 
ACUS11 KWNS 231716
SWOMCD
SPC MCD 231715
NCZ000-SCZ000-231815-

MESOSCALE DISCUSSION 0877
NWS STORM PREDICTION CENTER NORMAN OK
1215 PM CDT WED MAY 23 2012

AREAS AFFECTED...PARTS OF THE CENTRAL/ERN CAROLINAS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 231715Z - 231815Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...INITIAL TSTM DEVELOPMENT IS EXPECTED TO EXPAND NWD FROM
CENTRAL SC INTO CENTRAL NC...WITH ACTIVITY TENDING TO MOVE NEWD/NWD
AFFECTING ERN PARTS OF THESE STATES AS WELL.  ADDITIONAL TSTMS
SHOULD DEVELOP ALONG A NWD MOVING DIFFERENTIAL HEATING BOUNDARY
/WHICH CURRENTLY EXTENDED FROM ENEWD FROM 40 SW SOP TO 20 E FAY TO
10 NE EWN/. WW ISSUANCE IS BEING CONSIDERED...GIVEN THE LIKELIHOOD
FOR SOME OF THE TSTMS TO BECOME SEVERE THIS AFTERNOON.

DISCUSSION...TRENDS IN SURFACE ANALYSES DURING THE MORNING SHOWED A
NEARLY STATIONARY TROUGH EXTENDING FROM SRN SC NWD TO THE SC/NC
BORDER...NEAR 40 SW SOP...AND THEN FARTHER NNEWD THROUGH ERN VA TO
VICINITY OF DCA AND THEN THROUGH ERN PA.  SURFACE HEATING ALONG AND
E OF THIS BOUNDARY WITHIN A CLEAR SLOT EXPANDING NWD ACROSS MUCH OF
CENTRAL/ERN NC PER SATELLITE IMAGERY WILL CONTINUE TO SUPPORT
DESTABILIZATION.  THIS COMBINED WITH A MOIST BOUNDARY
LAYER...STEEPENING LAPSE RATES AND COLD MIDLEVEL TEMPERATURES MOVING
NWD ACROSS THE DISCUSSION AREA WILL SUPPORT MLCAPE EXCEEDING 1500
J/KG /WHICH WAS ALREADY INDICATED PER OBJECTIVE ANALYSES/.

SATELLITE IMAGERY SHOWED A DEEPENING CU FIELD INVOF THE SURFACE
BOUNDARY WHERE LOW LEVEL CONVERGENCE SHOULD BE MAXIMIZED AND COUPLED
WITH UPPER LEVEL DIFFLUENT FLOW FIELD FROM NRN SC THROUGH CENTRAL
NC.  STRONGER MID-UPPER LEVEL SLY WINDS/DEEP SHEAR ARE MAINLY
CONFINED ALONG AND OFFSHORE THE SC/NC COASTS TODAY.
HOWEVER...DESPITE WEAKER SHEAR EXPECTED WITH WWD EXTENT...THE
FAVORABLE THERMODYNAMICS AND FORCING FOR ASCENT ATTENDANT TO A
COUPLE OF EMBEDDED VORTICITY MAXES OVER THE CENTRAL CAROLINAS
SUGGEST SEVERE TSTMS WILL BE POSSIBLE WITH STRONG WIND GUSTS AND
HAIL THE PRIMARY THREATS.

..PETERS/WEISS.. 05/23/2012

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

ATTN...WFO...AKQ...MHX...RAH...ILM...RNK...CHS...CAE...

LAT...LON   33898121 34978008 36367914 36397737 36067625 35017678
            34237805 33697892 33147951 32858008 33248088 33898121

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 23, 1:44 PM EDT	Severe Thunderstorm Watch	SPC	Anson, Beaufort, Bertie, Bladen, Brunswick, Camden and 46 more	7 hr
May 23, 4:54 PM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Bladen, Brunswick, Camden, Chatham and 42 more	66 min
May 23, 7:32 PM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Bladen, Brunswick, Chatham, Chowan and 37 more	58 min

Nearby

Mesoscale Discussions in North Carolina, 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.