NHC SLOSH Run – Irene Advisory 29

CHPS Forecast on the lower Hudson

Irene’s Actual Flood Impact

Tropical Storm IreneAn opportunity to link SLOSH with the

Community Hydrologic Prediction System (CHPS) at NERFC

David R. Vallee, HIC NERFC

Outline

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

NERFC

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

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Background

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)

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What is CHPS? 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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What CHPS Looks Like?

Hydraulic Modeling 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

Forecast Services Successes

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

Forecast Services Successes

Incorporation of SLOSH into Hydraulic Modeling:1. Forecast w/in inches of morning flood/surge at POUN62. GFS MRPSSE ET Surge resulted in over-simulation of the earlier

overnight tide cycle3. Underforecast of the Albany crest (2 feet) (part tide/part rainfall )

Summary & Next Steps 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…

NHC SLOSH Run – Irene Advisory 29

CHPS Forecast on the lower Hudson

Irene’s Actual Flood Impact

Tropical Storm IreneAn opportunity to link SLOSH with the

Community Hydrologic Prediction System (CHPS) at NERFC

David R. Vallee, HIC NERFC