NOUS42 KCHS 031057
PNSCHS
GAZ087-088-099>101-114>119-137>141-SCZ040-042>045-047>051-031800-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
500 AM EDT THU JUN 7 2007

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

YOUR NATIONAL WEATHER SERVICE OFFICE IN CHARLESTON WILL ISSUE THE 
RIP CURRENT OUTLOOK IN THE SURF ZONE FORECAST FOR ALL 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. 

THE FACTORS THAT ARE USED FOR THE RIP CURRENT OUTLOOK ARE 
METEOROLOGICAL...OCEANOGRAPHICAL AND 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 SURFACE OF THE OCEAN 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 25 MPH OR GREATER.

THE OCEANOGRAPHICAL FACTORS WE USE ARE SWELL DIRECTION...HEIGHT AND 
PERIOD...AS WELL AS A PERSISTENCE FACTOR. WE LOOK FOR SWELLS THAT 
IMPACT THE COAST AS DIRECTLY AS POSSIBLE. AFTER DETERMINING WHAT 
DIRECTION THE SWELLS WILL BE OCCURRING FROM...WE LOOK FOR LONGER 
PERIOD WAVES OR SWELLS THAT PRODUCE HIGHER BREAKING WAVES AT THE 
COAST. THIS IN TURN LEADS TO STRONGER AND MORE FREQUENT RIP 
CURRENTS. THIS CAN FURTHER BE ENHANCED IF THERE ARE ALREADY CUTS IN 
THE SANDBAR FROM RECENT RIP CURRENTS. HENCE WE HAVE THE PERSISTENCE 
FACTOR.

FINALLY WE LOOK AT ASTRONOMICAL FACTORS. FIRST THERE IS THE FULL OR 
NEW MOON...WHEN WE HAVE THE ALIGNMENT OF THE SUN...EARTH AND MOON IN 
A STRAIGHT LINE. THE TIDAL PULL OF THE SUN JOINS THE TIDAL PULL OF 
THE MOON...RESULTING 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 WEEK. THIS IN TURN 
CAUSES A STRONG GRAVITATIONAL PULL OF THE MOON DURING THIS TIME.

AFTER DETERMINING THE FACTORS THAT WE EXPECT WE ASSIGN A VALUE TO 
EACH TO ARRIVE AT OUR FINAL FORECAST OF EITHER LOW...MODERATE OR 
HIGH HIGH RISK OF RIP CURRENTS.

IDEALLY...THE COMBINATION OF STRONG AND DIRECT ONSHORE WINDS... 
LARGE AND LONG PERIOD SWELLS IMPACTING THE COAST DIRECTLY...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 DO NEED TO STRESS THAT EVEN IN THE ABSENCE OF THESE FACTORS 
THERE CAN STILL BE RIP CURRENTS. AS A SAFETY PRECAUTION...ALWAYS 
HEED TO ADVICE OF LIFEGUARDS AND THE BEACH PATROL. PAY ATTENTION TO 
FLAGS AND POSTED SIGNS...SUCH AS THOSE NEAR BEACH ACCESS POINTS AND 
LIFEGUARD STATIONS.

WHEN YOU ARRIVE AT THE BEACH...SPEAK WITH ON DUTY LIFEGUARDS ABOUT 
THE RIP CURRENTS AND ALL OTHER WATER CONDITIONS EXPECTED FOR THE 
DAY.

TUNE IN TOMORROW FOR MORE INFORMATION ON RIP CURRENTS.

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