Update on Storm Surge at NCEP Dr. Rick Knabb, Director, National Hurricane Center and representing numerous partners 21 January 2014

NOAA/NWS Vision Improve storm surge guidance Produce water level analyses and forecasts that include all contributions to total water level: surge, tides, waves, fresh water, background anomaly Move from deterministic to probabilistic approaches Utilize multi-model ensemble Inundation products: provide information about water depth over land (inundation) above ground level (AGL) Communicating actionable information for decision makers, media, and the public

Social science research summary Insufficient public concern about storm surge, even among high-risk coastal residents Strong support for inundation graphic Strong support for separate storm surge warning

Are you in a zone? Public outreach emphasis: to know risk, then create appropriate hurricane (evacuation?) plan for family or business

New NHC inundation graphic What will drive inundation prediction? Experimental P-Surge % exceedance at each individual location Grids Latest SLOSH basins updated to NAVD88 Topography/DEMs NOAA CSC sea-level rise DEM (~5-10m), resampled to ~30 m Augmented with USGS NED ~30 Processing Locally using ArcGIS for Server and Desktop Working on automation for 2014 hurricane season

P-Surge Methodology Derive probabilistic guidance from a set of SLOSH (Sea, Lake, and Overland Surges from Hurricanes) model runs Ensemble is centered on NHC’s official advisory Error space is based on 5-year Mean Absolute Error (MAE); assumed normal distribution; and that MAE = sigma Error space is sampled via representative storms rather than via random sampling

P-Surge Methodology Why SLOSH? Efficient (100s of runs in 30 minutes with few CPU) Maintained as part of hurricane evacuation studies Parametric wind model for forcing Overland flooding

P-Surge 2.0 Enhancements SLOSH + Tide Each ensemble member defines time thereby allowing addition of a gridded tide Advantage: More accurate overland inundation Impact: More along track error samples (from 3 to 7) Most recent SLOSH basins Advantage: More accurate storm surge using modern vertical datum (NAVD-88) Impact: Slower run times due to higher resolution

P-Surge 2.0 Enhancements Above ground level as well as above datum Advantage: Enhanced communication as general users do not understand datums Impact: More files to process Time component Create (13) 6-hour cumulative and (13) 6-hour incremental probability products rather than (1) 80-hour cumulative probability product Advantage: Provides timing guidance Impact: Larger and more numerous files to process

NWS Storm Surge Warning Implementation Team Watch/warning definition and criteria Internal NWS watch/warning collaboration procedures Specifying needed development work, training, etc. Leverage and track relevant work funded by Sandy Supplemental Affects on and potential changes to wind warnings Affected products and content/format changes Dissemination mechanisms including EAS Discuss potential similar approach for extratropical surge

Next generation of storm surge models NOS working with NWS to develop and transfer into operations new tropical and extratropical storm surge models with finer resolution and tide, river, and wave effects Total water level surge models with ensembles Operational and research models have been evaluated within the Coastal Ocean Modeling Testbed ESTOFS: Extratropical Surge and Tide Operational Forecast System Experimental storm surge predictions for Hurricane Isaac (2012)

Joint Hurricane Testbed (JHT) Mission: Successfully transfer new technology, research results, and observational advances from research groups to operational centers Announcement of Federal Funding Opportunity (AFFO) for 7 th round projects published Aug 2012 New projects begun for , including: Blanton/Luettich, UNC: “A Visualization Application for Distributed ADCIRC-based Coastal Storm Surge, Inundation, and Wave Modeling”

Using ADCIRC for Tropical Cyclone Surge Prediction NOS and NWS using ADCIRC – its unstructured grids capture large storms like Sandy while providing local resolution ADCIRC combines effects of storm surge and tide Experimental 5-member ensemble provided to NHC via HFIP With Sandy Supplemental funding, a version will become operational on NCEP high performance computing system in FY2016 Model grid Model topobathy in Chesapeake

Experimental ADCIRC TC Predictions NHC Track Ensemble members for Isaac (2012): NHC track, shifted left, and increased intensity Shifted right within cone of uncertainty Ensemble for Sandy (2012)

Improving extratropical storm surge prediction Atlantic Extratropical Surge + Tide Operational Forecast System (ESTOFS) began in 2012 Computes surge with tides for forecasting and for coupling to Nearshore Wave Prediction System NOS developed with ADCIRC Coastal resolution ~3km GFS forcing 6-hr nowcast followed by 180-h forecast Pacific capability in development for FY14

Extra slides if needed

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

Rmax=25 mi (forecast) Surge Based on NHC -12 hr. Advisory

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

Rmax=40 mi Surge Based on NHC Storm Best Track