— the rip current program is coordinated by Jeff Orrock and Mike Colby. In the Wakefield, 

 Va., office — which includes Currituck County in North Carolina and the Virginia Beach area 



— the contact is Paul Houle. 



"Town officials and county leaders are checking it daily, and the forecasts have become 

 part of the television stations' weather broadcasts," Pfaff says. 



"Even local papers are helping us spread the word when the threat for strong rip currents 

 are high — and, along with other media outlets, they give NWS rip current forecasts more 

 public exposure," adds Pfaff, who received the Wilmington NWS office's "Isaac Cline 

 Award" for his outreach efforts. 



The North Carolina models are derived from groundbreaking work done in Florida. Early 

 work included forecasts by Jim Lushine of the Miami office of the NWS. Randy Lascody of 

 the Melbourne NWS office transferred the models to other areas within Florida. Also, a team 

 of Sea Grant rip current researchers at UF includes Bob Dean, Dan Hanes and Robert Thieke, 

 as well as several graduate students 



"We used to believe that the formation of rip currents was relatively spontaneous and 

 correlated with individual events such as large storms," says Dean. "Now, we're starting to 

 believe rip currents persist for longer time periods at various strengths — sometimes as long as 

 several weeks or months." 



Doctoral student Jamie MacMahan analyzed thousands of time-lapse images of a beach 

 stretch near the U.S. Army Corps of Engineers research facility in Duck, on the North Carolina 

 Outer Banks. He was able to correlate the images to wave data and other information from 

 offshore buoys. 



The images revealed dark swaths of the ocean, which the researchers describe as rip 

 current channels that are persistent in time. As weather and surf conditions varied, the swaths 

 expanded or shrank — but remained in the same general location even after most storms. 



Only a particularly large storm or hurricane moved the channels — and/or erased the 

 longshore sandbar system until a new rip channel formed. "We've identified some rip current 

 channels that start in May and last until September," MacMahan said. 



While rip channels may be fairly common, they become noticeable — and dangerous — 

 when the flow of water is sufficient to create a strong current, the researchers concluded. 

 Factors include storms that push large amounts of water toward shore, piling water into the gap 

 between the sandbar and beach. 



"One of the biggest misnomers is 'rip tide,'" MacMahan says. While rip currents are not 

 part of the tidal system, they can be influenced by tides that lower the beach elevation. 



The Sea Grant team also has found that when waves are breaking in a fairly solid line 

 parallel to the shore, the risk for rip currents is higher than if the breaks come at a rippling 

 diagonal toward shore. But if the angle of the breaking waves becomes too big, longshore 

 currents may form, rather than rip currents. 



To map the nearshore bathymetry — or flow of the ocean floor — along beaches in 

 Florida, the researchers put instruments on personal watercraft and deploy the instruments in 

 rip channels. Early this summer, the team will spend a month in Daytona Beach gathering 

 additional data. 



"We need more quantitative measurements, then we will be able to make better correla- 

 tions," MacMahan says. 



Continued 



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TOP TO BOTTOM: The red flag signals "no 

 swimming" if rip currents are present. In Kitty 

 Hawk, violators are fined $250. 

 Rip currents can be identified in aerial views. 

 To link to local forecasts, go to the National 

 Weather Service ofwww.ripcurrents.noaa.gov. 



COASTWATCH 9 



