Office of Coast Survey NOAA’s Storm Surge Modeling Capabilities Jesse C. Feyen Storm Surge Roadmap Portfolio Manager

Office of Coast Survey NOAA’s Tropical Storm Surge Products SLOSH-based storm surge products

Office of Coast Survey SLOSH: NWS’ Operational Surge Model The basis for tropical products and services Internal hurricane model driven by storm track, radius of maximum winds, and central pressure Uses domains (basins) which vary in resolution from several hundred meters near the coastline to a few kilometers offshore –Basins have sub-grid cell features to model barriers (such as levees or roadways) and Further info:

Office of Coast Survey Generating MEOWs and MOMs Primary purpose for SLOSH is to estimate potential surge for hurricane evacuation studies –NHC runs thousands of hypothetical storms through a basin to create composites of potential surge in the form of MEOWs and MOMs –More info: MEOW = Maximum Envelopes of Water Worst case snapshot for a particular storm category, forward speed, trajectory, and initial tide level, incorporating uncertainty in landfall location MOM = Maximum of Maximums Combines all MEOWs for a particular storm category

Office of Coast Survey How a MEOW is Assembled

Office of Coast Survey Predicting Imminent Events Real-time deterministic runs –National Hurricane Center (NHC) begins operational SLOSH runs when a hurricane watch is issued (48 hours before landfall) based upon NHC’s official forecast –Used by NHC and local Weather Forecast Offices to guide advisories and statements

Office of Coast Survey Deterministic Output for Ike (2008) But the prediction from one run is misleading because it ignores forecast uncertainty

Office of Coast Survey Hurricane Advisory – Approximately 12 hr. before landfall NHC TRACK ERROR 12 hr. OUT 133 mph, 933 mb.

Office of Coast Survey Actual Hurricane Track 30 mi. E of 12 hr. Advisory Forecast Track TRACK FORECAST ACTUAL TRACK 133 mph, 933 mb.

Office of Coast Survey Rmax=25 mi (forecast) Surge Based on NHC 12 hr. Advisory

Office of Coast Survey Rmax=40 mi Surge Based on NHC Storm Best Track

Office of Coast Survey Filling the Gap: P-Surge Probabilistic storm surge predictions Ensemble based on NHC forecast advisory –Perturbation of cross-track error, along-track error, intensity error, and size error Computes probabilities and exceedance heights –“Probability of water exceeding X feet” available on NHC’s website: –“Height exceeded by X%” of ensemble available at MDL: Available in.kml,.shp, GRIB2

Office of Coast Survey Perturbing the Forecast Include 90% of possible cross track error (roughly 3 times the size of the cone of error) Similar perturbations applied to size, speed, and intensity Results in hundreds of simulations

Office of Coast Survey Probability of > 5 feet of Storm Surge for Katrina Advisory 23 Provided – Ensemble of hypothetical storm runs – Associated weights Can compute – Probability of exceeding a certain height

Office of Coast Survey Height Exceeded by 10% of the Ensemble for Katrina Advisory 23 Provided – Ensemble of hypothetical storm runs – Associated weights Can compute – Height exceeded by a certain probability

Office of Coast Survey Pacific SLOSH Basins - MOMs and MEOWs haven’t been generated - Operational?

Office of Coast Survey SLOSH Display Package (SDP) Allows for viewing and exploring SLOSH data –Displays basins, MOMs, MEOWs, and historical storms for viewing and analysis –Can animate and explore native.rex files –Can output.shp and.kml SDP is intended to be used by trained emergency managers, FEMA personnel, and NWS forecasters Download:

Office of Coast Survey Extratropical Storm Surge (ETSS) Operational modeling system based on SLOSH –Uses a larger grid since it is a larger phenomena and driven by the Global Forecast System (GFS) model –96 hourly surge forecasts are made every 6 hours, 24 x 7 –Predictions given at points around U.S. coasts: –Visualizations also available:

Office of Coast Survey ET-Surge Website Combines Tide and Surge Forecasts

Office of Coast Survey Visualization of Gridded ETSS Predictions

Office of Coast Survey Coverage of ETSS

Office of Coast Survey Atlantic Extratropical Surge and Tide Operational Forecast System (ESTOFS) Purpose –Second operational set of forecast guidance for extratropical storms that covers the Western North Atlantic basin, Gulf of Mexico, and Caribbean Sea –Compute surge with tides, astronomical tides, and subtidal water levels (surge only) Pros –Incorporates the astronomical tides, lacking in current model –ADCIRC unstructured grid could improve coastal resolution Cons –No river inflows or seasonable water level adjustments –Insufficient grid resolution at rivers, inlets, and barrier islands

Office of Coast Survey ESTOFS-Atlantic Applies widely validated ADCIRC model East Coast 2001 tidal database grid (EC2001) 254,565 nodes Coastal resolution ≈ 3 km Specify the tidal forcing at 60 o W

Office of Coast Survey Operational Set-up 4 times per day running cycle –Time is 00z, 06z, 12z, and 18z Total 8 days simulation –12-hr nowcast followed by 180-hr forecast Surface forcing from GFS –10 m winds and sea level pressure every 3 hours Tidal forcing from OSU TPXO v6.2 Scheduled to be operational at NCO FY12 Q2

Office of Coast Survey ESTOFS Output Deliver three types of water level –Combined Water Level (CWL): Surge + tides –Harmonic Tidal Prediction (HTP): Astronomical tides –Subtidal Water Level (SWL): SWL = CWL – HTP Provide both field and point output –6 minute water level at points, hourly water level for fields Output on grid (NetCDF) and 2.5 km NDFD (GRIB2) 2009 Veteran’s Day Nor’Ida

Office of Coast Survey Water Level as Fields EC2001 grid (NetCDF)NDFD CONUS grid (GRIB2)

Office of Coast Survey Water Level as Fields EC2001 grid (NetCDF)NDFD CONUS grid (GRIB2)

Office of Coast Survey Hindcast Skill Assessment (ESTOFS CWL vs ETSS + CO-OPS TP + Anomaly) East CoastGulf of Mexico

Office of Coast Survey Ensemble Model Development Uncertainty in initial conditions Evaluate the extent of model predictability Model uncertainty: dynamics Model uncertainty: Physics Deterministic model only consider one IC Single model can not give us probability clue Only one numerical method for single model Only one set of physical parameterizations can be used

Office of Coast Survey