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Sea, Lake, and Overland Surge from Hurricanes

Learn about the SLOSH model, a computerized tool developed by the National Weather Service to estimate storm surge heights and winds caused by hurricanes. Explore the SLOSH data, installation process, display program, and more.

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Sea, Lake, and Overland Surge from Hurricanes

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  1. SLOSH Sea, Lake, and Overland Surge from Hurricanes

  2. Outline • Introduction – The SLOSH Model • Information about Storm Surge • SLOSH Data and Installation • SLOSH Display Program • Changing Basins • Displaying Storm Files • Animation within SLOSH • Display Options • Astronomical Tide Prediction • Exercise

  3. Introduction

  4. What is SLOSH? • Sea, Lake, and Overland Surge from Hurricanes • A computerized model developed by the National Weather Service (NWS) to estimate storm surge heights and winds resulting from historical, hypothetical, or predicted hurricanes. Source: http://www.nhc.noaa.gov/HAW2/english/storm_surge.shtml

  5. Storm Surge

  6. Wind 0’ 50’ 100’ 150’ 200’ Current Deep Water a. Top View of Sea Surface b. Side View of Cross Section “ABC” C B A Eye B C A MSL

  7. Wind Wind Wind STORM SURGE Current Landfall a. Top View of Sea Surface and Land b. Side View of Cross Section “ABC” Sand Dunes on Barrier Island C B A Eye 0’ 50’ 100’ 150’ 200’ MSL C B A Barrier Island Mainland Continental Shelf

  8. STORM SURGE STORM SURGE STORM SURGE HIGH TIDE MEAN TIDE (MSL) LOW TIDE DUNE DUNE Tide with Storm Surge

  9. SLOSH: Purposes • Determining the potential surge for a location • Basis for “hazard analysis” portion of coastal hurricane evacuation plans

  10. How does SLOSH work? Pressure Radius of Max Winds Topography Input Location Bathymetry Direction Forward Speed Storm Surge Heights Output

  11. Sub-grid elements: • 1 dimensional flow for rivers and streams • Barriers • Cuts between barriers • Channel flow with chokes and expansions • Increased friction for trees and mangroves Individual Grid Barrier Stair Step Rise Water Surface above a Square Transport Points Water Depth above a Square Surge Points DATUM

  12. SLOSH Model grid with geographic data at full resolution

  13. SLOSH Model grid with geographic data at finer resolution • Used by Basin Developer for quality control

  14. The SLOSH Model • Accuracy - generally within ±20% of peak storm surge • Accounts for astronomical tides • Does not include rainfall amounts, river flow, or wind-driven waves

  15. SLOSH Model Coverage • US East Coast and Gulf of Mexico Coastline • Parts of Hawaii, Guam, Puerto Rico and the Virgin Islands • Various basins in China and India

  16. Generalizations from SLOSH • More intense storms cause higher surges • Highest surges usually occur to the right of the storm track • Fast moving storms = high surges along the open coast • Slow moving storms = greater flooding inside bays and estuaries

  17. Generalizations from SLOSH • Larger storms affect longer stretches of coastline • Direction of storm approach often impacts the extent of flooding • Shallow slopes in the continental shelf allow greater storm surge with small waves • Storm surge is less in areas with steeper coastal slopes, but large breaking waves can occur

  18. Applications • To estimate potential storm surge and flooding for a given hurricane category, forward speed, and direction • To help hurricane evacuation programs by helping to define the areas at risk

  19. SLOSH Data and Installation

  20. SLOSH Package • SLOSH CD is available from NWS to any government employee with training working in the Emergency Management area • The CD contains: • SLOSH Display for Windows • Tide Display for Windows • Hurricane Tracking Program • SLOSH Data

  21. SLOSH Data • The National Weather Service has run several thousand hypothetical hurricanes for each basin with the SLOSH model • Resulting flooding data from each run is saved • SLOSH MEOW data is available for 39 basins

  22. 1. Run “Install.exe” from the “SLOSH Display CD-ROM” 2. Select “Install” SLOSH Installation

  23. 3. Select Components to Install Select “SLOSH Display Window” and “Tide Window” and hit “OK”

  24. 4. Set Target Directories 4a. Main Directory 4b. Data Directory C:\slosh.pkg 4c. Output Directory C:\slosh.pkg\data Hit “Enter” to Accept Default C:\slosh.pkg\output

  25. 5. Enter name for program group and select “OK” to begin installation SLOSH Package 6. After installation is complete, choose either to install SLOSH data or read data from SLOSH CD 7. Select “NO” 8. Installation Complete

  26. 9. Go to “Install SLOSH Data” 10. Highlight Basin Names 11. Select “Install” 12. Select “Next”

  27. Data Files of Historical Storms 13. Highlight Animation File Names 14. Select “Install” 15. Select “Done”

  28. SLOSH Display Program 1 Changing SLOSH Basins 3 Animating a Rex File 5 Tide Display 2 Displaying Storm Files 4 Display Options

  29. Initial State of SLOSH Display Program Toolbar Main Menu Bar

  30. Change Basin Screen Double click on outline of basin or basin name

  31. Basin Label SLOSH Grid Coordinates of Pointer Location

  32. Storm File Options Select Storm Window

  33. What is a MEOW? • Maximum Envelope of Water • Composite of maximum storm surge heights at each grid cell using hypothetical hurricanes run with the same: • Category • Forward Speed • Landfall Direction • Initial Tide Levels • Composite achieved by reviewing parallel tracks that make landfall at different locations • Over 80 MEOWs have been generated for some basins

  34. Direction of Hurricane Track Category of Hurricane Speed of Hurricane Select MEOW- Direction: NE Category: 3 Speed: 15 mph (mean)

  35. Color Coded Legend Storm Label Scales Color Coded Storm Surge Heights Storm Direction Arrows Water Height

  36. MEOW Category 3 NE Direction MEOW Category 3 NW Direction

  37. What is a MOM? • Maximum of MEOWs • Composite of the maximum storm surge height for all hurricanes of a given category • Disregards forward speed, landfall direction, landfall location, etc. • Only 5 MOMs per basin, i.e. one per storm category

  38. MOMs for Each Category at Mean Tide MOMs for Each Category at High Tide C4_MEAN.MS2 HI4_MOM.MS2 CATEGORY 4 CATEGORY 4 TIDE LEVEL = MEAN TIDE LEVEL = HI

  39. Storm Label

  40. Historical Storms • Not all basins have historical storms • File names containing a series of letters and numbers are actually MEOWs E105I0.ms2 Basin Tide Category Direction Forward Speed

  41. Historical Storms Basins where Historical Storms are available: • Apalachicola Bay agnes.apc • Bahamas andrwnhc.bha • Sabine Lake audrey.ebp • Fort Myers andrew.fmy • Virgin Island h1928.vir • Oahu, Hawaii oahu1.hnl • Puerto Rico h1928.sju

  42. Puerto Rico Basin Historic Storm of 1928 h1928.sju

  43. Display Options

  44. Toolbar • Arrow • Zoom In • Zoom Out • Pan • Ruler • Inquire All • Probe • Previous Zoom • Full Zoom

  45. ZOOM IN Zoom In Hot Button or Menu Display grid over SLOSH grid

  46. ZOOM OUT Zoom Out Hot Button or Menu

  47. RULER Ruler Hot Button or Menu

  48. Initial Point End Point Length of Current Segment Cumulative Length Measured MEASURING

  49. INQUIRE ALL Inquire All Hot Button or Menu Slidell, LA

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