A climatology of pressure jumps around the Gulf of Carpentaria

We present a climatology of pressure jumps, defined as a sharp rise in pressure of at least 0.3 hPa in three minutes, at stations around the Gulf of Carpentaria, based on one-minute data obtained from Bureau of Meteorology automatic weather stations in the region. We examine also data from one inland station, Daly Waters, which lies about 265 km west of the Gulf. Many of the pressure jumps are associated with bore-like disturbances, while others accompany seabreeze passages, or mark the onset of thunderstorm gust fronts. During the latter half of 2006, data are available at a sufficient number of stations to estimate the speed and direction of the disturbances. Bore-like disturbances tend to have two main directions of travel. The most common propagate predominantly from the northeastern sector and are associated with morning glory disturbances that originate over Cape York Peninsula. However, a number of disturbances originate south of the Gulf and subsequently propagate towards the north or northwest. These southerly morning glory disturbances are associated with the passage of cold fronts across central Australia, or are spawned within the inland trough following strong ridging across the continent. Of the 21 bore-like disturbances that were recorded at three or more stations during the four-month period August-November 2006, sixteen were from the northeastern sector and five originated south of the Gulf. One of the latter was recorded as far west as Daly Waters, where weak sea-breeze disturbances are common also, even though Daly Waters lies some 265 km inland from the Gulf. Only one northeasterly disturbance was identified at Groote Eylandt in the northwest of the Gulf.