Doppler radar allows the operator in many cases to see the feature known as the tornado vortex signature, which is an outgrowth of well developed mesocyclones. Being able to see this feature and its progression of intensity and lowering toward the ground is a great breakthrough in tornado warnings. When this feature is present tornadoes usually are forming and in most cases reach the ground. Since these features show up many minutes before the actual ground formation of the tornado, the meteorologist can issue warnings that are more timely and accurate. NOAA Photo showing strong mesocyclone over northern Oklahoma.
Red colors are winds away from the radar and green colors are towards the radar.
Purple colors are ambiguous velocities. There is a 100 knot shear from the red to the greens at the bottom portion of the storm. About the time this velocity data was taken a tornado was occurring near the strong shear. Doppler radar, due to the narrow beam width and high power output, gives a resolution never available to radar operators in the past. Features such as outflow winds , wind shear lines in areas of sparse or no precipitation, clear air signatures and other features can all be detected with the newer radars.