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

National Weather Service

SLOSHSLOSH

SSea, ea,

LLake, andake, and

OOverlandverland

SSurges fromurges from

HHurricanesurricanes

Part 1: W. Shaffer / MDLPart 2: B. Jarvinen / NHC


DEFINITIONS:DEFINITIONS:

STORM SURGESTORM SURGE is the increase in is the increase in water level due to a storm water level due to a storm (hurricane / tropical storm / high (hurricane / tropical storm / high winds).winds).

STORM TIDESTORM TIDE is the total water level is the total water level during a stormduring a storm

= Astro Tide + STORM SURGE= Astro Tide + STORM SURGE + Rainfall Runoff + Anomaly + Rainfall Runoff + Anomaly


bb

Storm tide 8.1 ft


Storm tide 8.1 ft

Predicted Tide0.9 ft


Storm tide 8.1 ft


Storm Surge = Storm Tide – Predicted tide


Storm tide 8.1 ft


Storm Surge = Storm Tide – Predicted tide = 8.1 – 0.9 = 7.2 ft


SLOSH Hurricane Storm SLOSH Hurricane Storm Surge ModelSurge Model

Solves shallow water equationsSolves shallow water equations

Orthogonal curvilinear grid Orthogonal curvilinear grid systemsystem

2-dimensional (2 ½ 2-dimensional (2 ½ dimensional ???)dimensional ???)



Overland floodingOverland flooding

Sub-grid Features:Sub-grid Features:

1-dimensional flow for rivers and 1-dimensional flow for rivers and streamsstreams

barriersbarriers

cuts between barrierscuts between barriers

channel flow, with chokes and channel flow, with chokes and expansionsexpansions

Increased friction for trees and mangrovesIncreased friction for trees and mangroves



DATUM

Stair Step RiseBarrier

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






Topo/BathyTopo/BathyData SourcesData Sources

USGS

NGDC

LSU




Embedded parametric Embedded parametric hurricane wind hurricane wind modelmodel

Uses a normalized wind profileUses a normalized wind profile

Solves diff eqn for wind speed and Solves diff eqn for wind speed and directiondirection (Direction is NOT specified (Direction is NOT specified a a prioripriori))

Uses pressure, not observed wind speedUses pressure, not observed wind speed

Forward speed incorporated into Forward speed incorporated into asymmetryasymmetry



Universal, not “calibrated” to locationUniversal, not “calibrated” to location

Utilizes “forecastable” hurricane Utilizes “forecastable” hurricane parametersparameters

Tested on MANY past hurricanesTested on MANY past hurricanes


INPUT TO SLOSHINPUT TO SLOSH

TRACK Positions - latitude & TRACK Positions - latitude & longitudelongitude

INTENSITY - (pressure drop)INTENSITY - (pressure drop)

SIZE - Radius of maximum SIZE - Radius of maximum windwind




Designed for hurricane Designed for hurricane evacuation evacuation planningplanning

Used as input to hydrology’s Used as input to hydrology’s DWOPERDWOPER river model – forecast hydrograph at river model – forecast hydrograph at selected locations used to initialize selected locations used to initialize wave which propagates up riverwave which propagates up river

Being used for Being used for real-timereal-time surge surge forecasting near landfall time forecasting near landfall time (beginning 24 hours before projected (beginning 24 hours before projected landfall)landfall)




Model output:Model output:

MOM’s and MEOW’sMOM’s and MEOW’s

Individual runs – in real timeIndividual runs – in real time

Historical hurricane runsHistorical hurricane runs

Probabilistic surge forecasts Probabilistic surge forecasts

Available inAvailable in

SLOSH display formatSLOSH display format

GIS format (ArcView or MapInfo)GIS format (ArcView or MapInfo)

Animations (on web)Animations (on web)



Not includedNot included currently: currently:

explicit tide explicit tide computationcomputation

wave setup and runupwave setup and runup



http://www.nws.noaa.gov/mdl/etsurge/


Verification of computed surges Verification of computed surges for past hurricanesfor past hurricanes




Documents

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