The bore-like character of three morning glories observed during the Central Australian Fronts experiment

Results of a field experiment carried out in 1991 as part of the Central Australian Fronts Experiment (CAFE) are presented. The data include daily early morning radiosonde soundings from Burketown in north Queensland, together with pressure, wind, temperature, and humidity data from an automatic weather station there. Sixteen morning glories were recorded at Burketown during the experiment. Surface data showed that the passage of a morning glory is accompanied by wind squalls, intense low-altitude wind shear and a sharp pressure jump at the surface. On all except one day, radiosonde soundings were carried out in the pre-morning glory environment. On seven days, additional soundings were carried out within an hour or two of the passage of a morning glory. Comparison of these with the pre-morning glory soundings is consistent with earlier inferences that disturbances are a type of internal undular bore. Unlike the one southerly morning glory for which data were obtained, the data for the northeasterly glories indicate significant horizontal temperature and moisture gradients in the post-morning glory air mass in most cases. Nevertheless, the observations are consistent with an internal undular bore generated in a horizontally inhomogeneous air mass.