NOUS42 KCHS 061239
PNSCHS
GAZ087-088-099>101-114>119-137>141-071100-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
739 AM EST WED FEB 6 2013

...GEORGIA SEVERE WEATHER AWARENESS WEEK CONTINUES THROUGH 
FRIDAY...

TODAY WE WILL DISCUSS TORNADOES. 

TORNADOES OCCUR RARELY AND IMPACT ONLY VERY SMALL AREAS AS
COMPARED TO THUNDERSTORMS...TROPICAL CYCLONES AND WINTER STORMS.
HOWEVER...AT THEIR WORST TORNADOES PRODUCE THE MOST VIOLENT WEATHER
ON EARTH.

MOST TORNADOES DEVELOP WHEN WARM...HUMID AIR AT THE SURFACE AND 
DRY...COLD AIR ALOFT COINCIDE WITH STRONG WINDS WHICH CHANGE 
DIRECTION AND SPEED WITH ALTITUDE...USUALLY NEAR A SURFACE LOW 
PRESSURE...WARM FRONT OR COLD FRONT. SUPERCELL THUNDERSTORMS
DEVELOP WITHIN THESE UNIQUE ATMOSPHERIC CONDITIONS...AND THESE 
ROTATING THUNDERSTORMS PRODUCE THE MAJORITY OF TORNADOES. 

A TORNADO FORMS AS AN INTENSE AND CONCENTRATED ROTATING COLUMN OF 
AIR WHICH EXTENDS BETWEEN A THUNDERSTORM AND THE GROUND. A FUNNEL IN 
CONTACT A BODY OF WATER BECOMES A WATERSPOUT. A FUNNEL NOT IN 
CONTACT WITH THE GROUND IS CALLED A FUNNEL CLOUD. SOMETIMES THE 
LOWER PORTION OF A FUNNEL IS NOT VISIBLE BUT IS STILL IN CONTACT 
WITH THE GROUND AND IS THUS DESIGNATED A TORNADO.  

WHEN A SIGNIFICANT THREAT FOR TORNADOES EXISTS...THE NATIONAL 
WEATHER SERVICE WILL ISSUE A TORNADO WATCH VALID FOR MULTIPLE 
COUNTIES...SOMETIMES ACROSS MULTIPLE STATES...VALID FOR SEVERAL 
HOURS. IF NATIONAL WEATHER SERVICE DOPPLER RADAR OR TRAINED SPOTTERS 
INDICATE THAT A TORNADO IS OCCURRING OR IMMINENT...THE NATIONAL 
WEATHER SERVICE WILL ISSUE A TORNADO WARNING FOR THE AFFECTED 
COUNTY...PART OF A COUNTY OR GROUP OF COUNTIES. TORNADO WARNINGS 
TYPICALLY LAST ONE HALF TO ONE HOUR. IF THE TORNADO THREAT 
PERSISTS...THE NATIONAL WEATHER SERVICE WILL ISSUE ADDITIONAL 
TORNADO WARNINGS.

IN RARE CASES...THE NATIONAL WEATHER SERVICE WILL DECLARE A TORNADO 
EMERGENCY IF CLEAR EVIDENCE EXISTS THAT A TORNADO PRESENTS A GRAVE 
THREAT TO LIFE AND IS PRODUCING CATASTROPHIC DAMAGE.     

TORNADOES OCCASIONALLY DEVELOP RAPIDLY WHEN NO WATCH OR WARNING IS
IN EFFECT. YOU SHOULD ALWAYS TAKE ACTION TO SAVE YOUR LIFE IF YOU
OBSERVE A TORNADO. 

HERE ARE SOME OTHER FACTS ABOUT TORNADOES...

SPRING IS THE MOST ACTIVE SEASON IN THE SOUTHEASTERN STATES...BUT 
TORNADOES CAN OCCUR ANY TIME OF YEAR. DURING THE LATE MORNING HOURS 
OF WEDNESDAY...JANUARY 30 2013...AN EF-3 TORNADO PRODUCED ONE 
FATALITY...MULTIPLE INJURIES AND EXTENSIVE DAMAGE ACROSS NORTHWEST 
GEORGIA INCLUDING AREAS WITHIN AND AROUND THE COMMUNITY OF 
ADAIRSVILLE. TORNADOES ARE ALSO PRODUCED BY DECAYING TROPICAL 
SYSTEMS DURING THE SUMMER AND AUTUMN. IN EARLY SEPTEMBER 2004...THE 
REMNANTS OF HURRICANE FRANCES SPAWNED 20 TORNADOES ACROSS SOUTHEAST 
GEORGIA AND SOUTH-COASTAL SOUTH CAROLINA.

NATIONAL WEATHER SERVICE TEAMS SURVEY STORM DAMAGE TO DETERMINE IF 
DAMAGE WAS PRODUCED BY A TORNADO OR BY STRAIGHT-LINE WINDS.
IF THE SURVEY CONFIRMS THAT A TORNADO OCCURRED...THE TEAM ASSIGNS A 
DAMAGE RATING BASED ON THE ENHANCED FUJITA SCALE. THIS SCALE RANGES 
FROM EF-0...A WEAK TORNADO WITH MINOR DAMAGE...TO EF-5...A VIOLENT 
TORNADO WITH INCREDIBLE DAMAGE.   

TORNADOES USUALLY MOVE FROM THE SOUTHWEST TO THE NORTHEAST AT
AN AVERAGE FORWARD SPEED OF 30 MPH. HOWEVER...TORNADOES SOMETIMES 
MOVE AS FAST AS 70 MPH AND CAN MOVE IN ANY DIRECTION. YOU SHOULD
NEVER ATTEMPT TO OUTRUN A TORNADO IN A MOTOR VEHICLE. 

TORNADOES REMAIN ON THE GROUND FOR WIDELY VARYING DISTANCES. THE 
TRI-STATE TORNADO OF MARCH 18 1925 REMAINED ON THE GROUND FOR OVER 
200 MILES FROM MISSOURI TO INDIANA. CONVERSELY...A TORNADO WHICH
TOUCHED DOWN IN NORTHERN BULLOCH COUNTY GA ON MARCH 26 2011 REMAINED 
ON THE GROUND FOR JUST OVER ONE-HALF OF A MILE. SOMETIMES A SINGLE 
SUPERCELL WILL PRODUCE MULTIPLE TORNADOES...KNOWN AS A TORNADO 
FAMILY...OVER A PERIOD OF HOURS AND OVER MANY MILES. 

TORNADOES IN THE SOUTHEASTERN UNITED STATES ARE FREQUENTLY MASKED BY 
HEAVY RAIN AND CANNOT BE VISUALLY OBSERVED. TORNADOES ALSO OCCUR AT 
NIGHT WHEN THEY CANNOT BE SEEN AND WHEN MANY PEOPLE ARE ASLEEP.  

TOMORROW WE WILL REVIEW THE DANGERS OF FLASH FLOODING. 

CHECK OUT ADDITIONAL SEVERE WEATHER AWARENESS WEEK INFORMATION ON 
OUR WEB PAGE AT WWW/ERH.NOAA.GOV/CHS/...AS WELL ON FACEBOOK AT 
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHARLESTONSC.GOV. YOU CAN 
ALSO FOLLOW @NWSCHARLESTONSC ON TWITTER.   

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