README.md SLOSH Help Pages Last Change: 2024-04-26
"Although SLOSH originated as a forecast model, it has recently [as of 1984] been used as a tool to delineate areas of potential hurricane flooding along the coast. With this information, an evacuation planner can identify areas for evacuation, determine which highways can be used for evacuation routes, and site shelters in areas not flooded or cut off by a hurricane." Jelesnianski, et. al., 1984
To estimate the potential flooding, "The SLOSH model is used by the NWS to create simulation studies to assist in the 'hazards analysis' portion of hurricane evacuation planning by FEMA, the U.S. Army Corps of Engineers, and state and local emergency managers. Thousands of [hypothetical] hurricanes with various combinations of categories (according to the Saffir-Simpson scale), forward speeds, track directions, and landfall locations are simulated to compute storm surge for each basin. Two composite products, Maximum Envelope of Water (MEOW) and Maximum of the MEOWs (MOM), are created in order to provide a manageable dataset for hurricane evacuation planners to access and display;" Glahn et al, 2009
The MEOW "lumps together a family of parallel track storms, all of the same category[, tide level, direction of motion,] and speed along the tracks. At each SLOSH grid square, the highest value of surge from the family of storms is displayed, giving a composite called the Maximum Envelope of Waters..." Shaffer, et al., 1986 "This product, then, displays the potential flooding for a hurricane of a given category, tide level, and general track direction and speed." Glahn et al, 2009
"A MOM is a composite of the maximum storm surge heights for all simulated hurricanes of a given category. There are typically five MOMs per basin (one per storm category), as results for forward speed, direction, and landfall location are aggregated... Thus, the MOM depicts the potential flooding for a given hurricane category [and tide level], regardless of landfall approach direction and speed. This product can be used by evacuation planners to designate evacuation routes and emergency managers to make early decisions." Glahn et al, 2009
With the development of the MEOWs and MOMs in the 1980's came a need to display these results to NWS's users. Since Geographical Information Systems (GIS) were not readily available, NWS's Meteorological Development Lab developed the SLOSH Display Program (SDP), a free GIS, to display the MEOW and MOM products. The SDP was first built for MS-DOS in the early 1990s and later rebuilt for MS-Windows (and linux) in the late 1990s.
The SDP was also given the ability, via a "Rex-file", to display animations of individual storms, whether they be historical, hypothetical, or predicted. The "Rex-file" contains snapshots of surge elevations and wind information at fixed time intervals (usually 10-15 minutes) as well as a final frame that holds the maximum level each grid cell attained during the run. The purpose of the animations, particularly the historical ones, is to validate the model, teach about the timing of surge and winds, and display historic storm surge levels.
While the SDP has for over 25 years (1990's to early 2020's) enabled interactions with MEOWs and MOMs, recent developments with online web services has eliminated that need. So the MEOWs and MOMs (which were last updated in the SDP in 2016) are being removed from the SDP.
As the remaining capabilities of the SDP are focused on education (see Rex-file above) and SLOSH model development, MDL has chosen to migrate the SDP to GitHub.
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