1. NHC SLOSH Run – Irene Advisory 29CHPS Forecast on the lower HudsonIrene’s Actual Flood Impact

2.  A bit about the NERFC & CHPS  Hydraulic Modeling of the lower Hudson  Event successes and challenges of incorporating SLOSH grids as the boundary condition for river forecasts at Poughkeepsie and Albany, NY

3.  Service area covers all 6 states of New England and much of New York State (less the Susquehanna River Basin)  180 forecast points  4 operational tidal segments  Poughkeepsie & Albany / Hudson  Middletown & Hartford / CT Rvr  Running USACE HEC-RAS  Boundary conditions:  NOS Astronomical Tides  GFS MRPSSE ET Surge  Hourly time steps

4. 4  For 3 decades NWS River Forecast System (NWSRFS) has been the NWS hydrologic forecasting foundation for over 30 years  NWSRFS architecture hindered use of recent advances in interactive forecasting and modeling  NWS needed an improved hydrologic modeling infrastructure to leverage community operational concepts and models as well as provide future products and services  The Community Hydrologic Prediction System (CHPS) is now operational at 10 of 13 RFCs, the rest will be over by the end of the year  For more information, see the NWS OHD CHPS web site (http://www.nws.noaa.gov/ohd/hrl/chps/index.html)http://www.nws.noaa.gov/ohd/hrl/chps/index.html

5. 5  CHPS is both a system and a concept  Open forecasting system to promote model & data sharing  NOAA reaching out to hydro community  CHPS uses Delft-FEWS from Deltares (Dutch Foundation) as core infrastructure  FEWS: Flood Early Warning System  Model adapter concept for algorithm modularity  Allows for dozens of hydrologic/hydraulic/hydro-dynamic models to run through these adapters within the system  Sophisticated data and workflow handling for models  Comprehensive forecaster user interface and displays (the IFD)  Highly configurable modeling environment via XML files  Initially, includes NWSRFS models and USACE models (HEC-RAS and HEC-ResSim)  Later, can include models from other providers

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7.  Hudson River (151 miles)  Albany – river mile 143.5  Poughkeepsie – river mile 73.9  Connecticut River (60 miles)  Hartford – river mile 51.8  Middletown – river mile 29.5  Daily boundary provided by NOS Tide + GFS ET Surge (MRPSSE) Connecticut River Hudson River

8.  Jamie Rhome, TPC Surge Group reached out to NERFC early Wed (prior to Irene) to work with us to incorporate SLOSH grids into HEC- RAS  Rob Shedd (DOH) and Alison MacNeil (Sr. Hydrologist) worked to:  Retrieve real-time runs & Extract appropriate time series data from SLOSH grid cells  Incorporate into our modeling system as a boundary condition for the Hudson and Connecticut Rivers applying the astronomical tide to the surge  Provide it as a forecaster modifier / time series which the forecasters could apply, smooth to or ignore

9. Incorporation of SLOSH into Hydraulic Modeling: 1.Forecast w/in inches of morning flood/surge at POUN6 2.GFS MRPSSE ET Surge resulted in over-simulation of the earlier overnight tide cycle 3.Underforecast of the Albany crest (2 feet) (part tide/part rainfall )

10.  Incorporation of SLOSH forcing on the lower Hudson and Connecticut improved NERFC forecasts of the Sunday morning surge/flood  Need to develop a more robust and streamline way for NERFC to obtain and extract necessary SLOSH information  NERFC wants to pursue the “Ensemble”  More testing and evaluation is necessary to identify deficiencies in NERFC modeling  NERFC at the mercy of tidal boundary forcing  SLOSH, ET Surge/GFS MRPSSE, etc…

11. NHC SLOSH Run – Irene Advisory 29CHPS Forecast on the lower HudsonIrene’s Actual Flood Impact