by Australian Gov. Bureau of Meteorology, September 2017
Tropical cyclones in the Australian region are influenced by a number of factors, and in particular variations in the El Niño – Southern Oscillation. In general, more tropical cyclones cross the coast during La Niña years, and fewer during El Niño years.
Analysis of historical tropical cyclone data has limitations due to a number of changes in observing practices and technology that have occurred over time. With new and improved meteorological satellites our ability to detect tropical cyclones has improved, as has our ability to differentiate tropical cyclones from other tropical weather systems such as monsoon depressions, which in the past may have been incorrectly named as tropical cyclones. A particularly important change occurred in the late 1970s when regular satellite images became first available from geostationary satellites above the Earth’s equator.
See also here