Windshear and Turbulence Warning System - Hong Kong

  • Overview
  • Project History

An operational Windshear and Turbulence Warning System (WTWS) was developed for Hong Kong's NewAirport at Chek Lap Kok. The WTWS provides alerts for terrain–and convective–induced windshear and turbulence. The system has been utilized by air traffic controllers and pilots since opening day, 6 July 1998. In addition to providing real–time windshear and turbulence alerts to controllers and pilots, the system provides up to 12–hour forecasts of terminal area turbulence to aviation meteorologists.

Note: The WTWS was previously known as the OWWS – the Operational Windshear Warning System.

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Hong Kong International Airport

Hong Kong's New Airport at Chek Lap Kok (CLK) is located on partly reclaimed land adjacent to Lantau Island, whose rugged terrain has a maximum elevation of nearly 1,000 meters (Fig. 1). Consequently, aircraft operating at the new airport may be affected by significant terrain-induced windshear and turbulence under certain meteorological conditions. In order to enhance safety and operational efficiency at the airport, Weather Information Technologies Inc. (WITI) developed a Windshear and Turbulence Warning System (WTWS) which was installed, tested and has been operational since the airport's opening day, 6 July 1998. Since 1998, the Hong Kong Observatory (HKO) has performed routine evaluations of the system and has made improvements to various sensing systems and wind shear and turbulence detection algorithms.

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Figure 1. Topographical map of the region near Hong Kong's new airport. The highest elevations are above 800 meters.


The 44–month project was under the sponsorship of the Hong Kong Observatory. The WTWS development team included WITI, the National Center for Atmospheric Research (NCAR), Hong Kong University of Science and Technology (HKUST), and the University of Wyoming.

Components include basic and applied research on wind flow over Hong Kong's terrain, a scientific field study, warning system concept and feasibility studies, system design, development, testing, implementation and training. The WTWS provides real–time hazardous weather information to air traffic controllers and pilots to enhance safety in the terminal area and improve predictions of hazardous weather to support strategic decision making by air traffic managers.

The WTWS is the first system worldwide to provide real–time alerts of terrain–induced turbulence and alerts for both convective and terrain–induced windshear, the WTWS also provides predictions of turbulence caused by terrain and airport surface wind as well as numerical weather prediction guidance. For detection of convective windshear, the WTWS relies partly on the output from a Terminal Doppler Weather Radar (TDWR) at Tai Lam Chung, about 12 kilometers from CLK. The windshear warning system ingests TDWR products including gust front, precipitation intensity, and storm motion, providing an integrated alert system. It generates graphics and text designed for easy interpretation by pilots, controllers, traffic managers and aviation forecasters. It also interfaces with other airport systems, reaching a broader user community including airport authority staff and airline offices.

Prior to the development of the windshear warning system, several studies were conducted in Hong Kong to gain insight into the meteorological conditions near the location of the new airport. These studies included analysis of routine weather observations, special observing programs and meteorological modeling of the differences between the existing Kai Tak Airport and the new airport. Variables that were analyzed included wind direction and speed, temperature, clouds, visibility, rainfall, thunderstorms and fog. Methods used to conduct these studies included investigative flights by light aircraft and water tank and wind tunnel experiments.

The probability of significant turbulence and windshear at Chek Lap Kok during specific meteorological conditions prompted the Hong Kong government to create the WTWS program. It was designed to investigate the detailed wind flow environment near the airport site and based on the scientific results, build and implement an operational windshear and turbulence warning and forecasting system. Following a competition, the project was awarded to Weather Information Technologies Inc. in October 1993.