Varied tropical climate
The Gulf region of the tropical savannas covers a considerable area. Its long narrow shape begins around the central-north of the Northern Territory and stretches in a south-easterly direction, following the southern coastline of the Gulf of Carpentaria, to finish in central north Queensland. Varied climatic patterns can occur in this tropical climatic zone as a result of its dimensions and location.
Intertropical Convergence Zone
A number of the Gulf's climatic gradients appear to be aligned with the coast as well as having a north-south component. The Intertropical Convergence Zone (ITCZ) lies across this region in summer and effectively divides the prevailing moist winds. The northern sections are dominated by the north-west monsoons and a modified south-east trade wind, known as a quasi-monsoon, reaches the south-east sectors from an easterly to north-easterly direction.
The ITCZ is associated with convergence and uplift of moist air and so produces heavy cloud and intensive rainfall. Average summer rainfall ranges between 400 mm in the south up to 800 mm in the north with moderate to high variability each year. Thunder days occur on 20-40 days each year but are more prolific in the far eastern sectors in Queensland. Droughts are more likely to occur in the drier southern regions where rainfall variability is greatest.
Relative humidity decreases away from the coast with January averages ranging between 40 per cent to 80 per cent and cloud cover is generally less than that of northern savanna sectors. Temperatures are hot with maximums around 36ºC and climate discomfort days occur on around 150 to over 200 days a year throughout the region. However, more frequent pleasant weather is recorded in the far north coastal sections and the extreme eastern areas in Queensland.
Winter conditions are dry and more stable with south-east trade winds extending over the entire region. Temperatures can drop, after warm sunny days, to an average overnight low of 12ºC. Humidity drops considerably from summer levels to 20-60 per cent and July skies are predominantly clear and sunny with little chance of rain.