The Integrated Terminal Weather System Terminal Winds Product

■ The wind in the airspace around an airport impacts both airport safety and operational efficiency. Knowledge of the wind helps controllers and automation systems merge streams of traffic; it is also important for the prediction of storm growth and decay, burn-off of fog and lifting of low ceilings, and wake vortex hazards. This knowledge is provided by the Integrated Terminal Weather System (ITWS) gridded wind product, or Terminal Winds. The Terminal Winds product combines data from a national numerical weather-prediction model, called the Rapid Update Cycle, with observations from ground stations, aircraft reports, and Doppler weather radars to provide estimates of the horizontal wind field in the terminal area. The Terminal Winds analysis differs from previous real-time winds-analysis systems in that it is dominated by Doppler weather-radar data. Terminal Winds uses an analysis called cascade of scales and a new winds-analysis technique based on least squares to take full advantage of the information contained in the diverse data set available in an ITWS. The weather radars provide sufficiently fine-scale winds information to support a 2-km horizontal-resolution analysis and a five-minute update rate. A prototype of the Terminal Winds analysis system was tested at Orlando International Airport in 1992, 1993, and 1995, and at Memphis International Airport in 1994. The field operations featured the first real-time winds analysis combining data from the Federal Aviation Administration TDWR radar and the National Weather Service NEXRAD radar. The evaluation plan is designed to capture both the overall system performance and the performance during convective weather, when the fine-scale analysis is expected to show its greatest benefit.