A Coastal Circulation Now/Forecast System for Texas-Louisiana Continental Shelf


K.-J. Joseph Yip, Matthew K. Howard and Robert O. Reid

Department of Oceanography

Texas A&M University, College Station, TX



An automatized continental shelf circulation forecast system (second generation) will be presented. This system has been providing predicted surface current on Texas-Louisiana continental shelf since May 1, 1999 for oil spill prevention project sponsored by Texas General Land Office (TGLO). The predicted surface currents is then transferred by Internet to TGLO for driving a dynamic trajectory model. There are 4 major components in this system: (1) forecast wind field retriving and preparation module, (2) shelf circulation model module, (3) simulation plotting module and (4) web display and file transfer module.

The wind field used in this system is a 3-hour interval ETA-22 forecast gridded wind from NCEP based on 00Z, 06Z, 12Z and 18Z model runs. A step-up temporal natural cubic spline interpolation is then implemented to obtain hourly gridded field primarily for the purpose of the model forecast simulations.

Early last year a modified version of Princeton Ocean Model (POM) to cover larger area which includes most of the Northern Gulf of Mexico (GOM) is implemented for a shelf circulation model module changeover. POM simulations, at the meantime, have focused on the use of realistic wind forcing, mixing and diffusion parameters, high resolution bathymetry, and climatological temperature and salinity for model initializations. Parameter tuning is also performed to optimize the wind-driven circulation simulation over the shelf. A series of POM nowcast simulations holding temperature (T) and salinity (S) fixed throughout the model runs, using realistic wind fields as driving force, and without data assimilation was carried out. Comparisons of the results from April to December of 1999 to the observation from TABS current meters were carried out as well. The TABS moorings chosen for the comparison are mooring P, B, D, J and K. The wind-driven simulations show reasonable qualitative agreement between TABS measurement and modeled currents at locations D, J, and K in April-May period, and at P, B and J in June-July period. These show noticeably strong inertial motions throughout the experimental period likely produced by onset of frontal events during April and May, and by diurnal wind event during June and July. From the experiments conducted demonstrate the feasibility of using POM for prediction of the shelf circulation.