FutureTP, NFAM,
Thank you very much for your information. It really helps.
Regarding the question about predictive windshear, in Hong Kong, windshear is either detected by radar or LIDAR. Radar works by calculating the Doppler frequency shift as NFAM has mentioned. The down side of using radar, however, is that it only works in rainy days (or when there is water droplets in the air).
LIDAR (Light Detection and Ranging system) works in a similar manner. The only difference is that it utilizes Laser detection so it still functions perfectly in the absence of water droplets. I am not sure if this system is used worldwide or only in places like Hong Kong where windshear is a very common phenomenon.
Correct me if I am wrong.
Chase