Available data have been collected concerning several events which appear to have been internal atmospheric bores over southern Australia. Two photographs are shown. one of a probable inland winter bore, the other of a summer bore over the sea. Data to hand suggest that internal atmospheric bores are commonly activated by gravity currents, and that at least initially, their propagation speed approximates that of the gravity current. The cold front accompanying the summertime bore is examined in as much detail as possible. It is found to have a very marked vortex structure near its leading edge, the wind behind the vortex being considerably less than the speed of propagation. The front assumed a bore-like character, including undulations, during its passage over the sea in the vicinity of Kangaroo Island, but reverted to being an unsteady gravity current on regaining the heated mainland, as shown by the rapid surface cooling. The probability of such a dual character is indicated by recent laboratory experiments.
R. H. Clarke (Sun,) studied this question.