Nowcast Protocol for the Great Lakes Forecasting System

by Chieh-Cheng J. Yen, Ohio State Univ, Columbus, United States,
Keith W. Bedford, Ohio State Univ, Columbus, United States,
David J. Schwab, Ohio State Univ, Columbus, United States,

Abstract: The Great Lakes Forecasting System is a cooperative federal-university undertaking designed to implement a predictive system for each of the Great Lakes. The desired forecasts concentrate on the physical status of the Lakes and include the three-dimensional distributions of the velocity and temperature as well as the water surface elevation and wind-wave distributions. Various aspects of the components of the integrated system have been described in previous articles and are predicated on the use of existing technology. One special exception, however, was the necessity of developing a fully functioning graphical user interface for control, tracking, steering and display of the system. The intended forecast template is analogous to the National Weather Service's in that a two-step procedure is required at the time a forecast is to be made. First, a hindcast procedure is invoked which, by comparing the predictions to the prior 24-hours of measured data, allows discrepancies to be examined and rectified in order to give the best model estimate of what is happening at the present time. Second, the forecast portion then proceeds by using the best estimate of present conditions as an initial condition with which to make the two-day predictions. To begin evaluating this forecasting template, an evaluation of the system's ability to predict the present status of the Lakes is being undertaken and is called nowcasting. The boundary conditions are the heat flux (which is calculated using objective analyzed Marine Observation data) and the wind stress (which is calculated using objectively analyzed FIBS (Fields by Information Blending and Smoothing) wind fields). Routine nowcasts based on these methods are beginning and this paper will report on elements of the nowcasting activity.

Subject Headings: Forecasting | Lakes | Velocity distribution | Stress analysis | Graphic methods | Data processing | Wind engineering | Great Lakes

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