WTWS graphical display.

Designers developed the WTWS products to enhance the safety, capacity and efficiency of operations at Chek Lap Kok by automatically providing pilots with concise windshear and turbulence alerts. The system also was designed to provide air traffic managers and supervisors with information to aid effective decision–making and to present high–resolution, real–time meteorological data and forecast guidance to forecasters.

The WTWS integrates data from various sensors and sources, including anemometers, Doppler weather radar, Doppler wind profilers, numerical weather prediction models and an array of global weather observations. Indirectly, it receives data from the ICAO world area forecast system (WAFS) and the World Meteorological Organization (WMO) global telecommunications system.

To enhance flexibility, the system was designed to run on commercially available Unix platforms. Modular system software, written in the C and Fortran programming languages, was designed to conform to international standards, allowing WTWS to run on vendor–neutral platforms. To heighten reliability, a redundant array of independent computers environment was employed. This ensures that all critical system processes are running somewhere on a network of WTWS computers. The capability to refine or tune system algorithms after, as well as before, installation is an important feature because optimization can be achieved only after it is used in an operational environment. The system also includes provisions for accommodation of new types of data, such as real–time aircraft and lidar data, after initial deployment.

An advanced version of the mesoscale model (MM5) developed by Penn State University and NCAR is used to predict atmospheric conditions around the new airport. The MM5 modelling system was adapted to provide real–time, short–range prediction of the mesoscale atmospheric conditions conducive to terrain–induced windshear and turbulence.

Although the MM5 produces weather guidance for the entire Hong Kong region, airport–specific forecasts are generated with a post-processing algorithm. Similar to model output statistics (MOS) techniques commonly used at major forecast centers, this algorithm provides 12–hour forecasts with 30–minute resolution of wind and turbulence at Chek Lap Kok.

The WTWS algorithms, many of which utilize an analysis technique known as 'fuzzy logic', produce turbulence and windshear products based on sensor data. This technique makes use of disparate data types and keeps important information throughout the decision process, maximizing algorithm performance. Sensor inputs include automatic weather stations, TDWR, and an aerodrome meteorological observing system – and each is used by specific windshear and turbulence detection algorithms. The weather product algorithms are used to produce gridded information, which is integrated using decision algorithms. By employing such a scheme, a new turbulence or wind shear algorithm can be added to the system by tailoring its output to a standardized format.