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National Weather Service SLOSH S ea, L ake, and L ake, and O verland O verland S urges from S urges from H urricanes H urricanes Part 1: W. Shaffer / MDL.

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Presentation on theme: "National Weather Service SLOSH S ea, L ake, and L ake, and O verland O verland S urges from S urges from H urricanes H urricanes Part 1: W. Shaffer / MDL."— Presentation transcript:

1 National Weather Service SLOSH S ea, L ake, and L ake, and O verland O verland S urges from S urges from H urricanes H urricanes Part 1: W. Shaffer / MDL Part 2: B. Jarvinen / NHC

2 National Weather Service DEFINITIONS: STORM SURGE is the increase in water level due to a storm (hurricane / tropical storm / high winds). STORM TIDE is the total water level during a storm = Astro Tide + STORM SURGE + Rainfall Runoff + Anomaly = Astro Tide + STORM SURGE + Rainfall Runoff + Anomaly

3 National Weather Service b Storm tide 8.1 ft

4 National Weather Service Storm tide 8.1 ft Predicted Tide 0.9 ft

5 National Weather Service Storm tide 8.1 ft Predicted Tide 0.9 ft Storm Surge = Storm Tide – Predicted tide

6 National Weather Service Storm tide 8.1 ft Predicted Tide 0.9 ft Storm Surge = Storm Tide – Predicted tide = 8.1 – 0.9 = 7.2 ft

7 National Weather Service SLOSH Hurricane Storm Surge Model Solves shallow water equations Orthogonal curvilinear grid system 2-dimensional (2 ½ dimensional ???)

8 National Weather Service SLOSH Hurricane Storm Surge Model Overland flooding Sub-grid Features: 1-dimensional flow for rivers and streams barriers cuts between barriers channel flow, with chokes and expansions Increased friction for trees and mangroves

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10 DATUM Stair Step Rise Barrier Dry and wetted grid squares. The squares are two-dimensional stair steps. Surge Points Transport Points Water Depth above a square Water Surface above a square Individual Grid

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15 Topo/Bathy Data Sources USGS NGDC LSU

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17 SLOSH Hurricane Storm Surge Model Embedded parametric hurricane wind model Uses a normalized wind profile Solves diff eqn for wind speed and direction (Direction is NOT specified a priori) Uses pressure, not observed wind speed Forward speed incorporated into asymmetry

18 National Weather Service SLOSH Hurricane Storm Surge Model Universal, not “calibrated” to location Utilizes “forecastable” hurricane parameters Tested on MANY past hurricanes

19 National Weather Service INPUT TO SLOSH TRACK Positions - latitude & longitude INTENSITY - (pressure drop) SIZE - Radius of maximum wind

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21 SLOSH Hurricane Storm Surge Model Designed for hurricane evacuation planning Used as input to hydrology’s DWOPER river model – forecast hydrograph at selected locations used to initialize wave which propagates up river Being used for real-time surge forecasting near landfall time (beginning 24 hours before projected landfall)

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23 SLOSH Hurricane Storm Surge Model Model output: MOM’s and MEOW’s Individual runs – in real time Historical hurricane runs Probabilistic surge forecasts Available in SLOSH display format GIS format (ArcView or MapInfo) Animations (on web)

24 National Weather Service SLOSH Hurricane Storm Surge Model Not included currently: explicit tide computation wave setup and runup

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27 National Weather Service Verification of computed surges for past hurricanes

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