One problem with your thoughts, the windmills are moving, it is not like a building. The radar display showing the farms changes, it comes and goes. The local weather guy has no answer.
http://www.roc.noaa.gov/windfarm/how_turbines_impact_nexrad.asp
HOW WIND TURBINES IMPACT THE NEXRAD DOPPLER WEATHER RADAR
Wind farms can impact coherent (Doppler) radars in three ways if the turbine blades are moving and they are within the radar’s line of sight. If close enough (within a few kilometers) they can partially block a significant percentage of the beam and attenuate data down range of the wind farm. They can also reflect energy back to radar and appear as clutter on the radar image and contaminate the base reflectivity data. The base reflectivity data is used by radar algorithms to estimate rainfall and to detect certain storm characteristics. Finally, they can impact the velocity and spectrum width data, which are also used by radar operators and by a variety of algorithms in the radar’s data processors to detect certain storm characteristics, such as mesocyclones, relative storm motion, turbulence, etc. The WSR-88D has a sophisticated clutter removal scheme. Since weather is always in motion, the scheme was designed to filter returns that have essentially no or very low motion. This is effective for removing the returned signals from terrain, buildings, and other non-moving structures. Unfortunately, the radar sees rotating wind turbine blades as targets having reflectivity and motion, hence processes these returns as weather.
Wind farms at “extremely close” ranges to radars have all the impacts listed above and additional ones. Inter-turbine scatter and multi-trip/multi-path returns create false signals down-radial from the real wind farm echo regions. These down-radial returns have been observed for turbines located within 10 miles (16 km) of the radar, and can extend down radial for 25 miles (40 km) or further. In some cases the disturbed areas are large enough to cause additional forecaster confusion and distraction, and to affect forecasts and radar data (particularly Velocity Azimuth Display Wind Profile) assimilations into numerical models.
If wind turbines are in the main radar beam and within 600ft (183m) of radars (in the near field), damage to both the radar’s and turbines’ electrical components might occur, Turbines within 1 mile of a NEXRAD can prevent the radar’s beam from properly forming, thus causing significant radar estimation errors down range from the turbines.
In summary, WTC can have negative impacts on radar capabilities and products (radar imagery) over and near the wind energy facility. This reduction of useable radar data can also impact weather forecast and warning operations, DoD military operations, and FAA air traffic routing operations. Examples of these impacts are:
Thunderstorm or winter storm characteristics could be masked or misinterpreted, reducing warning effectiveness in the vicinity of and downrange of the wind energy facility.
False signatures contaminating Doppler velocity data in the vicinity and downrange of the wind energy facility could reduce forecasters’ situational awareness, particularly during hazardous/severe weather events.
Data masking or contamination if thunderstorms develop over the wind energy facility may negatively impact warning effectiveness.
False precipitation estimates could negatively impact flash-flood warning effectiveness.
Needless and expensive FAA aircraft re-routing from false returns due to WTC.
But, as I indicated, the windmillls aren't going anywhere; they are readily distinguished from moving weather on a time-based display. Your mind/eye does that automatically.
Like I said, no big deal...