Abstract
The UHF Interferometric observation were conducted during the Rocket Triggered Lightning Experiment in Japan. The experiment site is located in the Hokuriku Area where we have frequent winter thunderstorms. The experiment was held during a winter thunderstorm season. During the project four data sets of the UHF radiation emitted by upward negative leaders which initiated positive ground strokes were recorded. The images of upward leader progressions were derived and the velocity of upward negative leaders as functions of time were estimated. The estimated results seem to be consistent with the former results obtained through optical observations.
