Alert archive / South Carolina / Tornado Watches in 2015

Tornado Watch 91

April 20, 2015Lincoln County, Georgia; 8 counties in South Carolina

The Storm Prediction Center issued this tornado watch at Apr 20, 2015, 4:36 PM EDT for Lincoln County, Georgia; 8 counties in South Carolina. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Apr 20, 2015, 4:36 PM EDT (20:36 UTC)
Expired
Apr 20, 2015, 10:00 PM EDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt

Counties Lincoln County, GA, Chesterfield County, SC, Edgefield County, SC, Fairfield County, SC, Kershaw County, SC, Lancaster County, SC, McCormick County, SC, Newberry County, SC, Saluda County, SC

The radar

The Columbia radar (KCAE), 47 km from the middle of the area, began a volume at 20:39 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
10%
Ten or more severe hail reports
30%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
60%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Apr 20, 6:23 PM EDTSevere Thunderstorm WarningCAELancaster22 min
Apr 20, 9:13 PM EDTSevere Thunderstorm WarningCAEEdgefield, McCormick32 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, 8.6 hours before the alert went out and 203 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 2015-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 51 joules per kilogram.LCLLFCEL10008507005003002001001 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 2015-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -7 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
51 J/kg
Mixed-layer CIN
-139 J/kg
Mixed-layer LCL
898 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
-7 m²/s²
0-3 km storm-relative helicity
10 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.

405 
WWUS20 KWNS 202029
SEL1  
SPC WW 202029
GAZ000-SCZ000-210200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 91
NWS STORM PREDICTION CENTER NORMAN OK
430 PM EDT MON APR 20 2015

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  EAST CENTRAL GEORGIA
  CENTRAL SOUTH CAROLINA

* EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 430 PM UNTIL
  1000 PM EDT.

* PRIMARY THREATS INCLUDE...
  A COUPLE TORNADOES POSSIBLE
  ISOLATED VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE
  ISOLATED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

SUMMARY...SEVERE THUNDERSTORMS OVER NORTHEAST GA AND UPSTATE SC WILL
BEING TO TRACK INTO WATCH AREA IN THE NEXT FEW HOURS.  LARGE HAIL
AND DAMAGING WINDS WILL REMAIN POSSIBLE WITH THE STORMS...ALONG WITH
A RISK OF ISOLATED TORNADOES.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 45 STATUTE
MILES EAST AND WEST OF A LINE FROM 45 MILES WEST SOUTHWEST OF
COLUMBIA SOUTH CAROLINA TO 90 MILES NORTH NORTHEAST OF COLUMBIA
SOUTH CAROLINA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 86...WW 87...WW 88...WW
89...WW 90...

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 25035.


...HART

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 20, 2:09 AM EDTSevere Thunderstorm WatchSPCCatoosa, Chattooga, Dade, Floyd, Gordon, Walker and 1 more4 hr
Apr 20, 3:36 AM EDTMesoscale DiscussionSPCCatoosa, Chattooga, Dade, Floyd, Gordon, Murray and 2 more84 min
Apr 20, 11:04 AM EDTSevere Thunderstorm WatchSPCAppling, Atkinson, Bacon, Baker, Ben Hill, Berrien and 25 more8 hr
Apr 20, 1:03 PM EDTMesoscale DiscussionSPCBanks, Clarke, Elbert, Franklin, Habersham, Hall and 7 more57 min
Apr 20, 1:23 PM EDTTornado WatchSPCBanks, Barrow, Clarke, Clayton, Cobb, Coweta and 22 more7 hr
Apr 20, 4:18 PM EDTMesoscale DiscussionSPCBanks, Barrow, Clarke, Elbert, Franklin, Habersham and 9 more57 min
Apr 20, 6:45 PM EDTMesoscale DiscussionSPCBanks, Barrow, Clarke, DeKalb, Elbert, Forsyth and 17 more60 min
Apr 19, 9:06 PM EDTMesoscale DiscussionSPCBladen, Brunswick, Duplin, Durham, Edgecombe, Franklin and 13 more54 min
Apr 20, 2:25 AM EDTMesoscale DiscussionSPCBeaufort, Bertie, Camden, Chowan, Craven, Currituck and 16 more95 min
Apr 20, 1:54 PM EDTMesoscale DiscussionSPCAlleghany, Stokes, Surry3 hr
Apr 20, 2:55 PM EDTSevere Thunderstorm WatchSPCAlamance, Alleghany, Anson, Ashe, Bertie, Caswell and 33 more7 hr
Apr 20, 6:27 PM EDTMesoscale DiscussionSPCAlamance, Alleghany, Caswell, Chatham, Durham, Forsyth and 16 more93 min

Nearby

Tornado Watches in South Carolina, 2015Tornado Watches in Georgia, 2015Every tornado watch in 2015

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.