Machine intelligent gust front detection for the Integrated Terminal Weather System (ITWS)
The Integrated Terminal Weather System (ITWS), currently in development by the FAA, will produce a fully-automated integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service sensors as well as from aircraft in flight in the terminal area. The ITWS will provide products to Air Traffic personnel that are immediately usable without further meteorological interpretation. These products include current terminal area weather and short-term (0-30 minute) predictions of significant weather phenomena. The Terminal Doppler Weather Radar (TDWR) will serve as a principle sensor providing data to a number of the ITWS algorithms. One component of the ITWS will be an algorithm for detecting gust fronts and wind shifts. A gust front is the leading edge of a cold air outflow from a thunderstorm. The outflow, which is deflected at the ground, may propagate many miles ahead of the generating thunderstorm, and may persist as an outflow boundary long after the original storm has dissipated. Gust fronts can have a significant impact on air terminal operations since they often produce pronounced changes in wind speed and direction, forcing a change in active runway configuration and rerouting of aircraft within in the terminal airspace. In addition, wind shear, turbulence, and cross-winds along the frontal boundary pose significant safety hazards to departing and landing aircraft. Reliable detection and forecasting of gust fronts and wind shifts will both improve air safety and reduce costly delays. Lincoln Laboratory has developed an Initial Operational Capability (IOC) Machine Intelligent Gust Front Algorithm (MIGFA) for the ITWS which currently utilizes TDWR and LL WAS or ASOS anemometer data and makes use of new techniques of knowledge-based signal processing originally developed in the context of automatic target recognition [Verly, 1989]. Extensions to the IOC to incorporate additional sensor or product data available under the ITWS (e.g., NEXRAD, terminal winds) are currently under development. MIGFA was first developed for the Airport Surveillance Radar with Wind Shear Processor (ASR-9 WSP). Its design and performance have been documented in previous reports by the authors [Delanoy 1993a]. This paper focuses on the design of the more recently developed TDWR MIGFA and its extension and adaptation to the ITWS (a more detailed description of the TDWR MIGFA can be found in Troxel [1994]). An overview of the signal processing techniques used for detection and tracking is presented, as well as a brief discussion of the wind analysis methods used to arrive at the wind shift and wind shear estimates. Quantitative performance analyses using data collected during recent field testing in Orlando, FL and Memphis, TN are presented. Test results show that MIGFA substantially outperforms the gust front detection algorithm used in current TDWR systems [Hermes, 1993] (MIGFA is currently under consideration as an upgrade option for TDWR).