12A.6 STORM SURGE MODELING FOR THE NEW YORK CITY METROPOLITAN REGION Brian A. Colle*, Malcolm J. Bowman, Robert E. Wilson, Frank Buonaiuto, Robert Hunter, Douglas Hill, Roger Flood, Yi Zheng, and Christian Mirche Storm Surge Research Group Marine Sciences Research Center Stony Brook University, Stony Brook, New York 1. INTRODUCTION New York City (NYC) and the adjacent part of New Jersey and Long Island surround a complex of waterways influenced by tides and weather. Much of the region is less than three meters above sea level, with about 260 square kilometers at risk for storm surge flooding from a 100-year flood for both tropical systems and nor-easter cyclones. To make matters worse, sea level has been rising at about 0.3 meters per century here; therefore, a 100-year flood may become a 30-year flood by 2090s. This is a conservative estimate since global warming is expected to increase the rate at which sea level will continue to rise to around 0.90 meters per century. This rise, combined with the likelihood of more frequent and intense storms, may turn a 100-year flood to a 40-80 year flood by the 2020s and even possibly a 4-year flood by the 2080s (Rosenzweig and Solecki 2001). Minor to moderate flooding has occurred in the NYC area for recent storms such as the December 1992 nor’easter, which illustrates the vulnerability of the region. During this event persistent 30-40 kt easterly winds over several tidal cycles pushed ocean water westward towards NYC and resulted in water levels at the Battery on the south side of Manhattan peaking at about 2.6 m (8.5 feet) above mean sea level. The water level only surpassed the sea wall by 1-2 feet for a few hours, yet the flooding entered the NYC subways and PATH system to New Jersey, thus requiring a shutdown of these transportation systems. If the storm had peaked only two feet higher, lives could have been lost (U.S, Army Corps of Engineers et al. 1995). Accordingly, coastal flooding around NYC is a major forecast problem for the NOAA National Weather Service (NWS). Considering the millions of people who live in the NYC region and the billions of dollars at risk, motivation exists to explore new modeling and observational technology in order to improve storm surge forecasting around NYC. For several years storm surge models have been utilized for landfalling hurricanes along the U.S. East Coast, such as the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model developed by the Techniques Development Laboratory of the NWS (Jelesnianski et al. 1992). The Pennsylvania State University-National Center for Atmospheric Research (NCAR) Mesoscale Model Version 5 (MM5) has been used for real-time predictions down to 4-km grid spacing across coastal New England for several years ________________________________________________ *Corresponding author address: Dr. Brian A. Colle, MSRC, Stony Brook University / SUNY, Stony Brook, NY 11794-5000. email: brian.colle@stonybrook.edu (Colle et al. 2003). The goal of this project is to use a state-of- the-art atmospheric model together with an ocean model to predict the storm surge for coastal New England during the warm and cool seasons. X Figure 1. (a) Full domain used for the storm surge model (ADCIRC) showing the triangular grids and bathymetry (color shaded in meters), which overlaps with the 12-km MM5 domain. (b) Zoom-in of a portion of the ADCIRC domain around NYC and Long Island. 2. MODEL SETUP The MM5 uses the Grell convective parameterization (Grell et al. 1994), simple ice microphysics (Dudhia et al. 1989), and the Medium Range Forecast (MRF) planetary boundary layer scheme (Hong and Pan 1996). Other details for the SBU real-time MM5 can be found in Colle et al. (2003).