Predictive Windshear Detection
The Airbus A330/A340 and probably other modern aircraft have a "predictive windshear detection system" PWS, to warn it's pilots about possible windshears or microbursts ahead after take-off or during final approach. (I am not talking about the "reactive windshear detection" which tells you that you are having an energy problem.)
While it is clear to me how to "use" this system, I would like to know how the PWS works and the physics-principles it is based upon. How is it using the weather radar??