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Malcolm J. Bowman

Abstract

A recurring mesoscale (diameter 100–150 km) baroclinic anticyclonic eddy lies proximate to the shelf break of the southeastern coast of the North Island of New Zealand new Cook Strait. Its appearance and persistence is interpreted in terms of a trapping mechanism suggested by Nof, which consists of an eddy-integrated dynamical balance formed between the β-induced equatorward force and a poleward directed pressure gradient attributed to an opposing southward flowing barotropic coastal current. For parameter values typical of the eddy, calculations show that alongshore coastal flows within the East Cape Current in the range of 2–10 cm s−1 would be sufficient to arrest and trap the eddy.

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New York City's Vulnerability to Coastal Flooding

Storm Surge Modeling of Past Cyclones

Brian A. Colle
,
Frank Buonaiuto
,
Malcolm J. Bowman
,
Robert E. Wilson
,
Roger Flood
,
Robert Hunter
,
Alexander Mintz
, and
Douglas Hill

New York City, New York (NYC), is extremely vulnerable to coastal flooding; thus, verification and improvements in storm surge models are needed in order to protect both life and property. This paper highlights the Stony Brook Storm Surge (SBSS) modeling system. It utilizes surface winds and sea level pressures from the fifth-generation Pennsylvania State University (PSU)-National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) or the Weather Research and Forecasting (WRF) model to drive the Advanced Circulation Model for Coastal Ocean Hydrodynamics (ADCIRC). For this study, the MM5 is utilized at 12-km grid spacing and ADCIRC is run on an unstructured grid down to ~10-m resolution in areas around Long Island and NYC.

This paper describes the SBSS and its performance across the NYC region during the 11–12 December 1992 nor'easter and Tropical Storm Floyd on 16–17 September 1999. During the 1992 event, east-northeasterly surface winds of 15–25 m s−1 (30–50 kts) persisted for nearly 24 h, while hurricane-force winds (35–40 m s−1) occurred for a few hours just south of western Long Island. This created a 1.0–1.5-m storm surge around NYC and western Long Island Sound over three tidal cycles. ADCIRC successfully simulated the peak water levels to within ~10%, and it realistically simulated some of the flooding across lower Manhattan. The surface winds for Tropical Storm Floyd were only 5–10 m s−1 weaker than the 1992 event, but no coastal flooding occurred during Floyd, because the storm approached during a low tide. Additional Floyd simulations were completed by shifting the storm's landfall to the spring high tide the previous week, and by doubling the wind speed to mimic a category-1 hurricane. A combination of the spring high tide and a category-1 hurricane scenario during Floyd would have resulted in moderate flooding at several locations around NYC.

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