Observations of a solitary wave train at Melbourne, Australia

On the morning of 6 January 1984, a series of four roll clouds were observed propagating across Port Phillip Bay, Melbourne. Spaced about 6km apart, the clouds were accompanied by regular oscillations in wind speed and direction and a sharp rise in surface pressure at the leading edge of the disturbance. Analysis of surface and upper air data suggests the roll clouds were associated with a family of solitary waves which had evolved from a long wave perturbation of the nocturnal boundary layer, in accordance with nonlinear wave theory. A synoptic-scale trough accelerating along the southern Victoria coastline was probably the source of the perturbation.