Ground Observation of Negative Sprites Over a Tropical Thunderstorm as the Embryo of Hurricane Harvey (2017)

We report on the observation of six red sprites produced by negative cloud-to-ground (CG) lightning strokes in a tropical thunderstorm that later evolved into Hurricane Harvey (2017). Most of these sprites conformed to the morphological characteristics of typical negative sprites previously observed over continental thunderstorms. The sprite-producing CG strokes were located in or near the deep convection region and their impulse charge moment changes all exceeded -500 C-km. During the sprite generation stage, the CG lightning stroke rate declined and the tropical thunderstorm structure appeared stable. Our analysis suggests that tropical marine meteorological systems, such as tropical disturbances, depressions, and thunderstorms are more likely to be main production systems of negative sprites. The frequent occurrence of 18 gigantic jets produced by the same thunderstorm further indicates that the thundercloud charge structures of sprite-producing oceanic thunderstorms are significantly different from that of continental thunderstorms.