Alert archive / North Carolina / Tornado Watches in 2011

Tornado Watch 256

April 28, 20115 counties in North Carolina; 5 counties in South Carolina

The Storm Prediction Center issued this tornado watch at Apr 28, 2011, 3:19 PM EDT for 5 counties in North Carolina; 5 counties in South Carolina. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Apr 28, 2011, 3:19 PM EDT (19:19 UTC)
Expired: Apr 28, 2011, 7:45 PM EDT
In force: 4 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 60 kt

Counties Bladen County, NC, Brunswick County, NC, Columbus County, NC, New Hanover County, NC, Pender County, NC, Florence County, SC, Georgetown County, SC, Horry County, SC, Marion County, SC, Williamsburg County, SC

The radar

The Wilmington radar (KLTX), 65 km from the middle of the area, began a volume at 19:20 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 40%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 40%
One or more hailstones of 2 inches or more: 30%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

3 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Apr 28, 3:24 PM EDT	Severe Thunderstorm Warning	ILM	Bladen, Columbus, Pender	51 min
Apr 28, 3:37 PM EDT	Tornado Warning	ILM	Bladen, Columbus, Pender	38 min
Apr 28, 4:10 PM EDT	Tornado Warning	ILM	Pender	40 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Charleston AFB, SC (KCHS), launched 12:00Z, 7.3 hours before the alert went out and 128 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: 1847 J/kg
Mixed-layer CIN: -17 J/kg
Mixed-layer LCL: 685 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 221 m²/s²
0-3 km storm-relative helicity: 251 m²/s²
Significant tornado parameter: 1.8
Supercell composite: 10.6

Open this sounding in Storm Lab

The text

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

175 
WWUS20 KWNS 281913
SEL6
SPC WW 281913
NCZ000-SCZ000-CWZ000-290000-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 256
NWS STORM PREDICTION CENTER NORMAN OK
315 PM EDT THU APR 28 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

       SOUTHEAST NORTH CAROLINA
       NORTHEAST SOUTH CAROLINA
       COASTAL WATERS

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 315 PM UNTIL
800 PM EDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 45 STATUTE
MILES EAST AND WEST OF A LINE FROM 55 MILES SOUTHWEST OF MYRTLE
BEACH SOUTH CAROLINA TO 30 MILES NORTH OF WILMINGTON NORTH
CAROLINA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 252...WW 253...WW
254...WW 255...

DISCUSSION...THUNDERSTORMS CONTINUE TO FORM OVER THE EASTERN
CAROLINAS AS LARGE UPPER TROUGH ROTATES ACROSS REGION.  SUFFICIENT
LOW LEVEL VERTICAL SHEAR WILL PROVIDE SUPPORT FOR SUPERCELLS THROUGH
THE AFTERNOON.  DAMAGING WINDS ARE THE MAIN THREAT...ALTHOUGH
ISOLATED TORNADOES WILL REMAIN POSSIBLE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24035.


...HART

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 27, 10:12 PM EDT	Mesoscale Discussion	SPC	Alleghany, Ashe, Forsyth, Rockingham, Stokes, Surry and 3 more	63 min
Apr 28, 12:09 AM EDT	Mesoscale Discussion	SPC	Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 25 more	36 min
Apr 28, 12:27 AM EDT	Mesoscale Discussion	SPC	Alamance, Alleghany, Ashe, Caswell, Davidson, Davie and 11 more	63 min
Apr 28, 12:41 AM EDT	Tornado Watch	SPC	Alamance, Alleghany, Ashe, Caswell, Davidson, Forsyth and 10 more	7 hr
Apr 28, 12:56 AM EDT	Tornado Watch	SPC	Alexander, Avery, Buncombe, Burke, Cabarrus, Caldwell and 21 more	4 hr
Apr 28, 3:30 AM EDT	Mesoscale Discussion	SPC	Alexander, Anson, Burke, Cabarrus, Catawba, Cleveland and 10 more	90 min
Apr 28, 4:30 AM EDT	Tornado Watch	SPC	Alamance, Anson, Bladen, Chatham, Cumberland, Davidson and 27 more	10 hr
Apr 28, 7:38 AM EDT	Tornado Watch	SPC	Bertie, Camden, Caswell, Chowan, Currituck, Gates and 9 more	7 hr
Apr 28, 8:05 AM EDT	Mesoscale Discussion	SPC	Anson, Chatham, Cumberland, Durham, Edgecombe, Franklin and 15 more	85 min
Apr 28, 8:48 AM EDT	Tornado Watch	SPC	Beaufort, Bladen, Brunswick, Carteret, Columbus, Craven and 15 more	7 hr
Apr 28, 11:22 AM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Bladen, Brunswick, Chowan, Columbus and 29 more	53 min
Apr 28, 2:41 PM EDT	Tornado Watch	SPC	Beaufort, Bertie, Camden, Carteret, Chowan, Craven and 21 more	6 hr
Apr 28, 6:33 PM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Camden, Carteret, Chowan, Craven and 20 more	57 min

Nearby

Tornado Watches in North Carolina, 2011 Tornado Watches in South Carolina, 2011 Every tornado watch in 2011

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.