Boundary-layer Oscillations from Thunderstorms at Sydney Airport

Analyses of wind velocity and air pressure data, acquired by a set of lowlevel anemometers at Sydney Airport, Australia, indicate the passage of a set of three remarkably smooth atmospheric boundary-layer oscillations that travelled ahead of a thunderstorm on 27 December 1991. The oscillations were probably generated by a nearby thunderstorm out ow, propagating into a stably strati ed atmospheric layer. It is likely that the phenomenon was initiated by the degeneration of an out ow gravity current into a family of amplitude-ordered solitary waves. Although reasonable agreement can be obtained on the propagation speed using a linear theory, the weakness of the trapping mechanism for this solution and an over-estimation of the weakly nonlinear wave half-width leads to a conclusion that the waves were fully nonlinear.