Over the last several years experiments were conducted with a pulsed Doppler radar that have significant consequences for hazard detection in the en route and terminal areas. Mesocyclones can be detected to over 250 km while tornadoes are seen to about 150 km. The radar can detect strong straight winds if they have a significant component along the beam. It is definitely demonstrated that aircraft measured turbulence correlates with the spread of the Doppler spectrum, but caution must be exercised in interpreting the Doppler spectrum width data because these are more prone to gross errors due to noise, antenna sidelobes, ground clutter, etc. Measurements of transient wind phenomena associated with thunderstorms near the airport require a suitably located radar, but it is not yet clear whether these can be always recognized. It appears that monitoring of winds along an aircraft glide path in clear air or otherwise is feasible.