What kind of radio/microwave frequencies should I use to make clouds/water reflect those waves back to my receiver?
where as a private TV station such as KCCI-TV in Des Moines only broadcasts at 270,000 watts
The NWS transmits at 750,000 watts of power for their S band [weather radar]
Surely that can't be average power? It must be instantaneous power for very short pulses. Possibly "chirped" to compensate for atmospheric dispersion.
That's ERP. Effective radiated power. Actual output power X antenna gain.