The SLOSH (Sea, Lake, and Overland Surges from Hurricanes) model computes
storm surge heights from tropical cyclones. SLOSH model coverage includes
all of the U.S.'s East and Gulf coastline, as well as parts of Hawaii,
Guam, Puerto Rico and the Virgin Islands. Various "basins" have also been
completed for the Peoples Republic of China and for India. An example of a
typical SLOSH "basin" is the Biloxi, Mississippi basin. A sample animation
of a model run (based on the National Hurricane Center's (NHC) best historical
track) is shown for Hurricane Hugo.
The SLOSH model is the basis for the "hazard analysis"
portion of coastal hurricane evacuation plans. Hundreds of hypothetical
hurricanes are simulated with various Saffir-Simpson categories, forward
speeds, landfall directions, and landfall locations. An envelope of high
water containing the maximum value a grid cell attains is generated at the
end of each model run. These envelopes are combined by the NHC into various
composites which depict the possible flooding. One useful composite is the
MEOW (Maximum Envelopes of Water) which incorporates all the envelopes for a
particular category, speed, and landfall direction. Another composite that
is useful to emergency managers is the MOM (Maximum of the MEOW's), which
combines all the MEOWs of a particular category.
Extratropical Storm Surge Forecasting (ET-Surge)
The extratropical storm surge model is driven by winds and
pressures derived from the NWS's Global Forecast Sytem (GFS) atmospheric model.
Coverage for the model as well as links to the forecasts can be seen here.
Probabilistic Storm Surge Forecasting (P-Surge)
The experimental Tropical Cyclone Storm Surge Probabilities
product consists of two graphics for the Gulf of Mexico and the Eastern
Atlantic coastal areas. The first graphic shows probabilities, in percent,
of storm surge exceeding 5 feet. The second graphic indicates there is a
10 percent chance of the displayed storm surge heights being exceeded.
These storm surge graphics are based upon an ensemble of Sea, Lake, and
Overland Surge from Hurricanes (SLOSH) model runs using the National
Hurricane Center (NHC) official advisory and accounts for track, size, and
intensity errors based on historical errors. Additional information on the
SLOSH model can be found at:
http://www.nhc.noaa.gov/HAW2/english/surge/slosh.shtml.
The experimental product is intended to provide users with
information which enhances their ability to make preparedness decisions
specific to their own situations. Customers have requested additional
tropical cyclone probabilistic information, and the National Research
Council's Fair Weather Report encourages probabilistic products. An
experimental period will be conducted from June 1- November 30, 2007, to
receive input from users to determine the benefits and usefulness of the
product and the product formats.
Coastal Waves
We undertake Coastal wave modeling to complement the
Evaluation Branch's storm surge models and to provide coastal and marine wave
forecasts. We have developed a numerical model which calculates maximum wind
speed and predicts hurricane generated sea waves along the hurricane's track.
Several hindcast studies have been performed for recent hurricanes. The
parametric high wave model is meant to be used with the ocean spectrum wave
model which cannot resolve the strong wind surrounding the eye wall. As
waves propagate into the coastal zone, shallow water wave models predict
wave shoaling, refraction, and breaking.
In the very near shore, breaking waves cause wave set-up in
the surf zone on the foreshore beach. The wave set-up at the shoreline may be
as high as 1 meter, which significantly enhances coastal flooding. A field
test at the U.S. Army Corps of Engineers' research facility in Duck, North
Carolina shows the observed wave set-up during the winter (extratropical)
storm of January 1998.