Introduction to Potential Hurricane Flooding

“Although [the Sea Lake and Overland Surges from Hurricane] SLOSH [model] 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

What are MEOWs and MOMs?

To estimate potential flooding, as part of the National Hurricane Program, the SLOSH model is used by the NWS to compute storm surge impacts from thousands of hypothetical hurricanes in various computational domains (aka basins). Each model run produces an envelope which is the maximum water level attained in each grid cell at any time during the run. The envelopes are then combined into MEOWs and MOMs which are provided to the Army Corps of Engineers as the hazards analysis portion of hurricane evacuation planning. The Army Corps then combines the information with population and roadway information to create the evacuation plans that are provided to FEMA and local emergency managers.

Maximum Envelope of Water (MEOW) 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…” 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

Maximum of the MEOWs (MOM) “A MOM is a composite of the maximum storm surge heights for all simulated hurricanes of a given category… Thus, the MOM depicts the potential flooding for a given hurricane category and tide level, regardless of landfall approach direction and speed.” Glahn et al., 2009.

SDP’s Original Purpose

Because Geographical Information Systems (GIS) were not readily available in the 1980s and early 1990s, NWS’s Meteorological Development Lab created the SLOSH Display Program (SDP) as a free GIS tool to display the MEOW and MOM products. Originally built for MS-DOS, it was later rebuilt for MS-Windows and Linux in the late 1990s.

By the early 2020s, modern web services replaced the need for an offline MEOW and MOM viewer. In 2026, the MEOW and MOM products (last updated in the SDP in 2016) were discontinued from the software, and the project migrated to GitHub to focus purely on model development and historical animations.