UCAR training helps forecasters predict rip currents

06/30/05

BOULDER--Innovative online courses developed at the University Corporation for Atmospheric Research are helping forecasters protect the public from rip currents. These narrow, fast-moving currents carry around 100 U.S. swimmers to their deaths each year, and lifeguards rescue some 50,000 others ensnared in the deadly flows.

UCAR's Cooperative Program for Operational Meteorology, Education and Training (COMET) is producing a set of Web-based modules for the National Oceanic and Atmospheric Administration. The modules will acquaint forecasters at NOAA's National Weather Service with the physics behind rip currents and help them use wind and wave forecasts to produce outlooks of rip-current risk. Pioneered in Miami, these NWS outlooks now serve much of the U.S. East Coast and Gulf Coast, as well as southern California.

"The rip-current forecasting in Miami has helped publicize the danger, both locally and regionally," says James Lushine, a forecaster in the NWS Miami office. "The local media routinely highlight when the rip current risk is high."

COMET meteorologist Kevin Fuell is working with instructional designer Katherine Olson and a team of COMET education and graphics specialists to produce the rip-current modules, which are available to the public on the Web. Two are already online, and two more are forthcoming (see below). The modules include some of the first-ever animated depictions of rip-current evolution in three dimensions.

"Weather forecasters are familiar with the atmosphere, but they often don't have a background in physical oceanography," says Fuell. "Our goal is to help them understand the processes that occur in the nearshore environment and use the limited observations and computer model data available to forecast the daily rip-current hazard." Fuell notes that most university departments of meteorology require no coursework in oceanography.

Rip currents typically develop at low points, or cuts, in sandbars, as the return flow from breaking waves rushes back to sea. Rip-current locations are dictated by natural and human-made coastal features such as piers, erosion barriers, and offshore canyons, as well as sandbars.

"Breaking waves deposit water near shore in a nonuniform manner," says Fuell. As this water flows and converges along the shore, its path of least resistance back out to sea is through sandbar cuts.

Although large breaking waves can trigger rip currents at any point in the tidal cycles, the currents are most hazardous around low tide. Other factors, such as widely spaced swells and a long period of onshore wind flow, can add to the risk.

As the rip current outlooks expand to more NWS offices, forecasters will combine the COMET training with their knowledge of local coastal features. Much like a tornado or hurricane watch, the public outlooks give a generalized risk of rip currents (identified as low, medium, or high). When rip currents appear imminent, lifeguards and local officials may close beaches or take other action.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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