Storm surge modeling for the New York City metropolitan region

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 during both tropical systems and nor-easters. Minor to moderate flooding has occurred in the NYC area for recent storms such as the December 1992 nor-easter and tropical storm Floyd in September 1999. As a result, coastal flooding for this region is a major forecast problem for the NOAA National Weather Service.

The Stony Brook storm surge group has developed a real-time storm surge model for the NYC region using both high resolution atmospheric and ocean models. The atmospheric forcing used for the Stony Brook Storm Surge (SSBS) modeling system is the Penn State- National Center for Atmospheric Research (PSU-NCAR) Mesoscale model (MM5), which has been in running twice-daily around for the Northeast U.S. and offshore waters for several years. The surface winds and sea-level pressure from the 12-km MM5 domain are used to drive the Advanced Circulation Model for Coastal Ocean Hydrodynamics (ADCIRC) model, which solves time-dependent, free-surface circulation and wind-driven transport problems in a barotropic configuration. The triangular elements of ADCIRC range from 70-km several hundred kilometers offshore to nearly 8-m around NYC.

This poster will describe the setup of SSBS and its performance for recent NYC storm events, such as Floyd (1999) and the 25 December 2002 nor-easter. During these events, which were well simulated by the MM5 in the 24-48 h time frame, the easterly surface winds were 30-40 kts, which created a 0.5-1.0 m storm surge around NYC. ADCIRC was able to successfully simulate the surge to within 5-10 cm in many locations. We will also show some of the long-term verification results from this past 2004-2005 winter as well as early attempts to use the Stony Brook MM5/WRF ensemble modeling system, in which 18-members of MM5/WRF are run each day at 12-km grid spacing. The eventual goal is to develop probabilistic methods to warn emergency managers of impending flooding in NYC. In addition, storm surge barriers were put into the ADCIRC model to also explore their feasibility in protecting the city during storm events as mean sea-level continues to rise during the next century. Users are able to monitor the SSBS 48-h forecasts and verification at http://stormy.msrc.sunysb.edu.