Hurricane Irene Northeast River Forecast Center In-brief

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Tropical Storm IreneAn opportunity to link SLOSH
with the Community Hydrologic Prediction System
(CHPS) at NERFC David R. Vallee, HIC NERFC
NHC SLOSH Run Irene Advisory 29
CHPS Forecast on the lower Hudson
Irenes Actual Flood Impact
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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

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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.h
  tml)

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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-dy
  namic 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?
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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)

Hudson River
Connecticut River
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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

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Forecast Services Successes

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

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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

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Tropical Storm IreneAn opportunity to link SLOSH
with the Community Hydrologic Prediction System
(CHPS) at NERFC David R. Vallee, HIC NERFC
NHC SLOSH Run Irene Advisory 29
CHPS Forecast on the lower Hudson
Irenes Actual Flood Impact