Tornadoes
| Probability of 2 or more tornadoes |
Mod (40%)
|
| Probability of 1 or more strong (F2-F5) tornadoes |
Low (20%)
|
| Probability of 10 or more severe wind events |
Mod (30%)
|
| Probability of 1 or more wind events > 65 knots |
Mod (30%)
|
| Probability of 10 or more severe hail events |
Low (10%)
|
| Probability of 1 or more hailstones > 2 inches |
Low (10%)
|
| Probability of 6 or more combined severe hail/wind events |
High (70%)
|
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 866
NWS STORM PREDICTION CENTER NORMAN OK
430 PM EDT THU OCT 13 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
DISTRICT OF COLUMBIA
SOUTHERN MARYLAND
EASTERN VIRGINIA
COASTAL WATERS
EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 430 PM UNTIL
1100 PM EDT.
TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE
MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH OF WASHINGTON
DISTRICT OF COLUM TO 35 MILES EAST SOUTHEAST OF RICHMOND
VIRGINIA. 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.
DISCUSSION...A SMALL CLUSTER OF SUPERCELLS HAS EVOLVED THIS
AFTERNOON INVOF OF A WARM/QUASI-STATIONARY BOUNDARY WHERE AIR MASS
IS MOIST AND MODERATELY UNSTABLE WITH MLCAPE OF AROUND 1000 J/KG.
THOUGH AMBIENT VERTICAL SHEAR IS NOT PARTICULARLY
STRONG...VERTICALLY VEERING WIND PROFILES COUPLED WITH THE MOIST/LOW
LCL BOUNDARY LAYER AND VORTICITY ENHANCEMENT ALONG THE SURFACE
BOUNDARY WILL ENHANCE LOW-LEVEL STORM ROTATION AND THE POTENTIAL FOR
A FEW TORNADOES.
