Yeh theres a graph I read once. It depends on sink rate at the time vs rate of speed loss in knots/sec. Heres some WS-threshold figures I extracted and comitted to memory for Mode 7:
In level flt the WS alert will activate with 2.3kt/sec rate of decreasing headwind or higher.
In a 1000fpm sink, WSA activates with 1.0kt/sec rate of decr HW or higher
At 2000fpm sink, WSA activates with ANY sustained rate of HW loss.
At 3000fpm sink, WSA activates with anything less than +1kt/sec rate of decr HW or higher (figure THAT one out!)
These thresholds themselves can vary according to available climb perf, FPA, and SAT fluctuations (rapid colder rather than rapid hotter). Exact figures on these items I dont know nor give a rats about but I notice they do make a diference at times.
That graph had the new-fangled predictive WINDSHEAR CAUTION range for EGPWS but you said Bally your not interested. And neither am I to be honest. WS alerts make enough damn racket without this bloodey CAUTION thing thrown in too.