The "striated delta' cloud system - a satellite imagery precursor to major cyclogenesis in the eastern Australian-western Tasman Sea region

Abstract

A distinctive upper-tropospheric cloud pattern, frequently a precursor to major extratropical cyclogenesis within the eastern Australian-western Tasman Sea region, has been identified from an examination of Geostationary Meteorological Satellite imagery. This cloud feature is usually triangular- (or delta) shaped, approximately symmetrical, composed of cirrus level cloud tops, and associated with transverse banding. Thirty-seven of these cloud systems, referred to as "striated deltas' (SDs), were detected within the study region between 1980 and 1991. Approximately 75% of these cases were associated with the development of storms of at least gale force intensity within 24 h of formation of the SD. Most of these intense developments were characterized by a 12-h period of explosive deepening. -from Author