Services Directory Login

SLOSH_2022 (Map Service)


View In:    ArcGIS JavaScript   ArcGIS.com   WMTS  

Current Version: 10.81

Service Description:

The Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model is a numerical model used by National Weather Service (NWS) to compute storm surge. Storm surge is defined as the abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Flooding from storm surge depends on many factors, such as the track, intensity, size, and forward speed of the hurricane and the characteristics of the coastline where it comes ashore or passes nearby. For planning purposes, the NHC uses a representative sample of hypothetical storms to estimate the near worst-case scenario of flooding for each hurricane category.

Hurricane category legend

SLOSH employs curvilinear polar, elliptical, and hyperbolic telescoping mesh grids to simulate the storm surge hazard. The spatial coverage for each SLOSH grid ranges from an area the size of a few counties to a few states. The resolution of individual grid cells within each basin ranges from tens to hundreds of meters to a kilometer or more. Sub-grid scale water features and topographic obstructions such as channels, rivers, and cuts and levees, barriers, and roads, respectively, are parameterized to improve the modeled water levels.

NHC provides two near worst case scenario planning products based on hypothetical storm tracks: Maximum Envelopes of Water (MEOWs) and Maximum of Maximums (MOMs). MEOWs are created by computing the maximum storm surge resulting from up to 100,000 hypothetical storms simulated through each SLOSH grid of varying forward speed, radius of maximum wind, intensity (Categories 1-5), landfall location, initial water level, and storm direction. A MEOW product is created for each combination of category, forward speed, storm direction, and initial water level. SLOSH products do not include Category 5 storms north of the NC/VA border. For each storm combination, parallel storms make landfall in 5 to 10 mile increments along the coast within the SLOSH grid, and the maximum storm surge footprint from each simulation is composited, retaining the maximum height of storm surge in a given basin grid cell. No single hurricane will produce the regional flooding depicted in the MEOWs. SLOSH model MOMs are an ensemble product of maximum storm surge heights. MOMs are created for each SLOSH basin by compositing all the MEOWs, separated by category and initial water level, and selecting maximum storm surge value for each grid cell regardless of the forward speed, storm trajectory, or landfall location. The MOMs represent the worst case scenario for a given category of storm and initial water level under ideal storm conditions. A high tide initial water level was used for the storm surge hazard maps.

This product uses the expertise of the NHC Storm Surge Unit to merge the operational SLOSH grids to build a seamless map of storm surge hazard scenarios using the MOM product. Each individual SLOSH grid for the Category 1-5 MOMs are merged into a single, seamless grid. The seamless grid is then resampled, interpolated, and processed with a Digital Elevation Model (DEM, i.e. topography) to compute the storm surge hazard above ground for each hurricane category. It should be noted that the SLOSH MOM storm surge hazard data used to create these maps are constrained by the extent of the SLOSH grids users should be aware that risk due to storm surge flooding could extend beyond the areas depicted in these maps. The resulting dataset is then reclassified into the bins described in the entity overview.  The areas marked with a value of "99" represent certain levee areas, such as the Hurricane and Storm Damage Risk Reduction System in Louisiana. These areas are highly complex and this product should not be used to assess the storm surge hazard within these areas.  Users are urged to consult local officials for flood risk inside these levee areas. Not all levee areas are included in this analysis - in particular, local features such as construction walls, levees, berms, pumping systems, or other mitigation systems found at the local level may not be included in this analysis.

Storm Surge Hazard Maps: https://www.nhc.noaa.gov/surge/nationalsurge/
SLOSH Model: https://www.nhc.noaa.gov/surge/slosh.php
Potential Storm Surge Flooding Map: https://www.nhc.noaa.gov/surge/inundation/

Complete metadata are available in the GIS data layers available from https://www.nhc.noaa.gov/nationalsurge/

These SLOSH data were downloaded by the Massachusetts Office of Coastal Zone Management on 2024-02-21 and clipped to the Massachusetts offshore boundary. MassGIS received a tile package from MassCZM and published it as a hosted tile layer in ArcGIS Online.



Map Name: Layers

Legend

All Layers and Tables

Layers: Description:

The Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model is a numerical model used by National Weather Service (NWS) to compute storm surge. Storm surge is defined as the abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Flooding from storm surge depends on many factors, such as the track, intensity, size, and forward speed of the hurricane and the characteristics of the coastline where it comes ashore or passes nearby. For planning purposes, the NHC uses a representative sample of hypothetical storms to estimate the near worst-case scenario of flooding for each hurricane category.

Hurricane category legend

SLOSH employs curvilinear polar, elliptical, and hyperbolic telescoping mesh grids to simulate the storm surge hazard. The spatial coverage for each SLOSH grid ranges from an area the size of a few counties to a few states. The resolution of individual grid cells within each basin ranges from tens to hundreds of meters to a kilometer or more. Sub-grid scale water features and topographic obstructions such as channels, rivers, and cuts and levees, barriers, and roads, respectively, are parameterized to improve the modeled water levels.

NHC provides two near worst case scenario planning products based on hypothetical storm tracks: Maximum Envelopes of Water (MEOWs) and Maximum of Maximums (MOMs). MEOWs are created by computing the maximum storm surge resulting from up to 100,000 hypothetical storms simulated through each SLOSH grid of varying forward speed, radius of maximum wind, intensity (Categories 1-5), landfall location, initial water level, and storm direction. A MEOW product is created for each combination of category, forward speed, storm direction, and initial water level. SLOSH products do not include Category 5 storms north of the NC/VA border. For each storm combination, parallel storms make landfall in 5 to 10 mile increments along the coast within the SLOSH grid, and the maximum storm surge footprint from each simulation is composited, retaining the maximum height of storm surge in a given basin grid cell. No single hurricane will produce the regional flooding depicted in the MEOWs. SLOSH model MOMs are an ensemble product of maximum storm surge heights. MOMs are created for each SLOSH basin by compositing all the MEOWs, separated by category and initial water level, and selecting maximum storm surge value for each grid cell regardless of the forward speed, storm trajectory, or landfall location. The MOMs represent the worst case scenario for a given category of storm and initial water level under ideal storm conditions. A high tide initial water level was used for the storm surge hazard maps.

This product uses the expertise of the NHC Storm Surge Unit to merge the operational SLOSH grids to build a seamless map of storm surge hazard scenarios using the MOM product. Each individual SLOSH grid for the Category 1-5 MOMs are merged into a single, seamless grid. The seamless grid is then resampled, interpolated, and processed with a Digital Elevation Model (DEM, i.e. topography) to compute the storm surge hazard above ground for each hurricane category. It should be noted that the SLOSH MOM storm surge hazard data used to create these maps are constrained by the extent of the SLOSH grids users should be aware that risk due to storm surge flooding could extend beyond the areas depicted in these maps. The resulting dataset is then reclassified into the bins described in the entity overview.  The areas marked with a value of "99" represent certain levee areas, such as the Hurricane and Storm Damage Risk Reduction System in Louisiana. These areas are highly complex and this product should not be used to assess the storm surge hazard within these areas.  Users are urged to consult local officials for flood risk inside these levee areas. Not all levee areas are included in this analysis - in particular, local features such as construction walls, levees, berms, pumping systems, or other mitigation systems found at the local level may not be included in this analysis.

Storm Surge Hazard Maps: https://www.nhc.noaa.gov/surge/nationalsurge/
SLOSH Model: https://www.nhc.noaa.gov/surge/slosh.php
Potential Storm Surge Flooding Map: https://www.nhc.noaa.gov/surge/inundation/

Complete metadata are available in the GIS data layers available from https://www.nhc.noaa.gov/nationalsurge/

These SLOSH data were downloaded by the Massachusetts Office of Coastal Zone Management on 2024-02-21 and clipped to the Massachusetts offshore boundary. MassGIS received a tile package from MassCZM and published it as a hosted tile layer in ArcGIS Online.



Copyright Text: NOAA National Hurricane Center (NHC) Storm Surge Unit, Mass. Office of Coastal Zone Management, MassGIS

Spatial Reference:
102100

Single Fused Map Cache: true

Capabilities: Map,TilesOnly,Tilemap

Tile Info:
Initial Extent:
Full Extent:
Min Scale: 4943216.0
Max Scale: 0.0

Min LOD: 7
Max LOD: 16

Units: esriMeters

Supported Image Format Types: MIXED

Export Tiles Allowed: true
Max Export Tiles Count: 100000

Resampling: true

Document Info: