An interesting radar phenomena occurred early Sunday morning, when the National Weather Service Doppler radar actually detected cars moving quickly along Interstates 80 and 55! Doppler radar measures the speed of motions toward and away from the radar, typically it measures the motions of rain and water droplets, however this wasn’t the case early Sunday morning. During the predawn hours a strong temperature inversion developed above the ground, which caused some of the energy from the radar beam to get re-directed toward the ground. In the doppler radar image below small pixels of fast motions toward and away from the radar are being detected up and down I-80 and I-55 southwest of Joliet, this is actually Doppler radar detecting the fast moving vehicles along the interstate! Click here for more information on how doppler radar works.