During September of 1979, the Arecibo Observatory 430 MHz Doppler radar was used to study the upper troposphere and lower stratosphere during thunderstorm activity in the afternoon hours. It was found that when the clouds developed sufficiently in the vertical direction to reach the height of the tropopause, gravity-wave oscillations in the vertical velocity above the tropopause would develop. The amplitude was 2 m/s, and the period was close to 6 min.