Severe hail storm - Brisbane, Queensland

The following report describes a violent thunder and hail storm which occurred over the Brisbane City area in the late afternoon of the 27th September 1955. Description of the actual hail storm is from observations at the Brisbane Weather Bureau but the synoptic and aerological sounding conditions over southeast Queensland are presented as explanation of the storm development. The hail was unusual from three aspects, namely the size and peculiar formation of conglomerates and the prolonged period during which precipitation vas only in the form of Massive falling stones. The synoptic situation was typical of spring thunder-storm weather but the aerological sounding at the regional radiosonde station was striking in its depth of about 30,000 feet of instability and 20,000 feet of sub-freezing temperatures in the instability layer. It is considered that this instability with the appropriate low level warmth and moisture was sufficient in itself to promote a severe thunder and hail storm but a diffuse cold front evidently passed over the area and could have contributed to the intensity of the storm. The existence of a sharp upper trough would also have contributed to uplift.