Rip Currents in the Great Lakes
Characterization,
Forecast, and Warning
Rip
currents are shore-normal, rapid seaward
flows that originate in the surf zone. As a hidden
but lethal hazard at Great
Lakes beaches, rip currents can quickly sweep
swimmers away from the shore out to the open, deep
water. It has been estimated by the Great
Lakes Current Incident Database that every
summer an average 12 fatalities and 26 rescues are
related to rip currents during from 2002 to 2012.
Rip currents sometimes are incorrectly referred as “undertows”
or “rip
tides”; however, those are three
different phenomena. Undertow is the backwash
of breaking waves and in general a weak flow. On the
other hand, rip tides are strong offshore currents
caused by the constricted tidal flow through barrier
beaches. In comparison, rip currents are strong,
non-periodical, discretely located, and more
dangerous than the other two types of offshore
currents. Rip currents are in general caused by
spatial difference in wave breaking along the
shoreline; however, the mechanism for generation of
rip current can be complicated and varies on a
beach-to-beach basis. To improve beach hazard
rip-current warning, we will develop an
Integrated Nowcast (real-time) Observation and
Forecast (future) Operation System (INFOS) and
applying the INFOS at three rip-current prone
beaches through coordination, communication, and
community outreach and education. The three beaches,
(i) Park
Point Beach, Duluth, MN, (ii) Mckinley
and Bradford Beach, Milwaukee, WI, and (iii) North Beach,
Port Washington, WI, are identified as high
occurrence of bar-gap, headland, and
structured-induced rip currents, respectively. The
proposed project is an integrated and collaborative
effort among partners: UW-Madison,
Minnesota/Wisconsin Sea Grants, Wisconsin Coastal
Management Program, National Weather Service at
Duluth and Milwaukee/Sullivan, City of Duluth,
Milwaukee County, and City of Port Washington,
NOAA-NOS and Great Lakes Environmental Research
Laboratory. Several news related to the INFOS-rip
current project can be accessed here.
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