NOUS42 KCHS 090913
PNSCHS
GAZ087-088-099>101-114>119-137>141-SCZ040-042>045-047>051-091000-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
510 AM EDT THU JUN 8 2006

RIP CURRENT AWARENESS WEEK CONTINUES TODAY WITH THE CHARLESTON 
NATIONAL WEATHER SERVICE RIP CURRENT PROGRAM.

FOR THE FIRST TIME EVER THE NATIONAL WEATHER SERVICE OFFICE IN 
CHARLESTON WILL ISSUE THE RIP CURRENT OUTLOOK FOR ALL THE BEACHES 
FROM THE SOUTH SANTEE RIVER IN SOUTH CAROLINA...TO THE ALTAMAHA 
SOUND IN GEORGIA. 

THE OUTLOOK IS BASED ON VARIOUS FACTORS THAT METEOROLOGISTS AT THE 
CHARLESTON OFFICE HAVE DETERMINED ARE IMPORTANT IN THE DEVELOPMENT 
OF RIP CURRENTS. THIS OCCURRED AFTER ANALYZING SEVERAL YEARS OF DATA 
OBTAINED FROM THE CHARLESTON COUNTY LIFEGUARDS...THE NATIONAL DATA 
BUOY CENTER OBSERVATIONS AND NEWSPAPER ACCOUNTS.

THE FACTORS THAT WE USE FOR THE RIP CURRENT OUTLOOK ARE 
METEOROLOGICAL...OCEANOGRAPHICAL AND EVEN ASTRONOMICAL. 

THE METEOROLOGICAL FACTORS ARE WIND DIRECTION AND WIND SPEED. THE 
WIND DIRECTION IS BASED ON A PREVAILING DAYTIME WIND AT THE AREA 
BEACHES. USUALLY THE MORE ONSHORE THE WINDS AND THE RESULTING 
DIRECT ONSHORE MOVEMENT TO THE OCEAN WATER ARE THE FIRST CRITERIA 
WE USE. SECONDLY...WE LOOK FOR THE HIGHER WIND SPEEDS...ALTHOUGH THE 
STRONG ONSHORE WINDS ALONE ARE USUALLY NOT ENOUGH TO PRODUCE RIP 
CURRENTS UNLESS SPEEDS ARE NEAR 25 MILES AN HOUR OR HIGHER.

THE OCEANOGRAPHICAL FACTORS WE USE ARE SWELL HEIGHT AND SWELL 
PERIOD...AS WELL AS A PERSISTENCE FACTOR. THE LONGER PERIOD WAVES OR 
SWELLS PRODUCE HIGHER BREAKING WAVES AT THE COAST...WHICH IN TURN 
CAN LEAD TO MORE RIP CURRENTS. THIS IS EVEN MORE SO IF THERE ARE 
ALREADY CUTS IN THE SANDBAR FROM RECENT RIP CURRENTS. HENCE THE 
PERSISTENCE FACTOR.

FINALLY WE LOOK AT ASTRONOMICAL FACTORS. FIRST THERE IS THE FULL OR 
NEW MOON. WHEN THIS OCCURS WE HAVE THE ALIGNMENT OF THE SUN...EARTH 
AND MOON IN A STRAIGHT LINE...AND THE TIDAL PULL OF THE SUN JOINS 
THE TIDAL PULL OF THE MOON. THIS RESULTS IN AN ADDITIONAL GRAVITATIONAL
PULL ON THE EARTH. ANOTHER ASTRONOMICAL FACTOR IS THE 
PERIGEE...WHICH IS WHEN THE MOON IS AT ITS CLOSEST APPROACH TO THE 
EARTH EVERY 4 WEEKS. THIS IN TURN CAUSES A STRONG GRAVITATIONAL PULL 
OF THE MOON DURING THE PERIGEE.

AFTER DETERMINING THE FACTORS THAT ARE EXPECTED AT THE BEACHES WE 
ASSIGN A VALUE TO EACH...AND FINALLY ARRIVE AT EITHER A LOW 
RISK...MODERATE RISK OR HIGH RISK OF RIP CURRENTS.

IDEALLY THE COMBINATION OF A STRONG AND DIRECT ONSHORE COMPONENT TO 
WINDS AND WAVES...LARGE AND LONG PERIOD SWELLS...CUTS IN THE SANDBAR 
FROM RECENT DAYS...AND THE OCCURRENCE WITHIN 24 HOURS OF BOTH THE 
PERIGEE AND EITHER THE FULL OR NEW MOON...WILL LIKELY CAUSE THE BEST 
CHANCE OF RIP CURRENTS AT THE BEACHES. 

BUT WE NEED TO STRESS THE POINT THAT EVEN IN THE ABSENCE OF THE 
FACTORS THERE CAN STILL BE RIP CURRENTS. AS A SAFETY 
PRECAUTION...ALWAYS HEED THE ADVICE OF LIFEGUARDS OR THE BEACH 
PATROL. PAY ATTENTION TO FLAGS AND SIGNS POSTED NEAR BEACH ACCESS 
POINTS AND LIFEGUARD STATIONS.

WHENEVER YOU ARRIVE AT THE BEACH...SPEAK WITH ON DUTY LIFEGUARDS 
ABOUT RIP CURRENTS AND ALL OTHER WATER CONDITIONS EXPECTED FOR THE 
DAY.
  
TUNE IN TOMORROW FOR MORE INFORMATION ON RIP CURRENTS.

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