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MDL's Evaluation Branch

  Main Storm Surge Verification

Hurricane Storm Surge Forecasting (SLOSH)

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:

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.

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    National Oceanic and Atmospheric Administration
    National Weather Service
    Meteorological Development Laboratory
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    Silver Spring, MD 20910
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    Page last Modified: November 08, 2012.
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