Split of a Thunderstorm into Anticyclonic and Cyclonic Storms and Their Motion as Determined from Numerical Model Experiments

Abstract

Abstract Since the concept of a rotational thunderstorm was presented by Byers in 1942, little attention has been paid to this important characteristic. Through direct and indirect observations, as well as a series of numerical experiments, the authors, some 24 years later, now postulate that many large thunderstorms are rotating. The numerical experiments revealed that a thunderstorm in a strong environmental wind field deviates to the left of the mean wind unless it rotates slowly and cyclonically. It was also found that the maximum deviation, either to the right or left, occurs when such a thunderstorm rotates with a critical tangential speed of only a few meters per second. This striking result contradicts the conventional expectation that the faster the rotation, the larger the storm's deviation. Further investigation of numerically produced clouds revealed that most of the peculiar motion of thunderstorms can be simulated by computing the momentum of clouds through step-by-step integration. A thunde...