The Circulation and Water Level Forecast Atlas: A New Product in Development at NOS

Abstract

The National Ocean Service (NOS) is developing a new product aimed at improving the prediction of water level and currents in key waterways of the united States. The Circulation and Water Level Forecast Atlas will provide a series of charts and graphs for predicting the tide and tidal current anywhere in a particular estuary, and for providing information on the effects of wind, barometric pressure, and river discharge. The atlas will be produced using a numerical hydrodynamic model implemented for a particular estuary using an extensive oceanographic and meteorological data set. The atlas will represent the circulation at many more locations than the traditional NOS Tidal Current Charts, which represent currents only at those locations where current data have been obtained and analyzed. The additional locations will include those of special navigational or environmental interest where current measurements cannot be made using traditional moored current meters. The additional spatial coverage resulting from the use of a numerical model will be especially evident in the atlas' tidal height charts, which will depict the changing water level over the entire waterway for each hour of the tidal cycle. On each chart coheight lines will traverse the entire waterway; tide predictions will no longer be limited to a few coastal locations. Use of a numerical hydrodynamical model, combined with the results of statistical data analyses, will also allow the synthesis of important meteorological and river effects in a way that will permit factors be applied to the tide or tidal current prediction based on wind, pressure, or river discharge information available to a user. In a waterway where NOS real-time water level gages are in operation, the atlas will supplement the NOS data retrieval software package called TIDES ABC, by providing a means to extrapolate the real-time data from these gages to other locations in the waterway. The first Circulation and Water Level Forecast Atlas is planned for Delaware River and Bay, where NOS conducted a 2 1/2-year circulation survey. The observations from that survey will be used to implement and assess the skill of the high-resolution numerical model that will be used to produce the atlas.