Tropical Cyclone Yasi

Last update: Wednesday 2 February 2011 at 3:30 pm BST:

Severe Tropical Cyclone Yasi made landfall just south of the city of Cairns at approximately midnight Australian Eastern Standard Time (2:00 pm British Standard Time). Yasi is producing wind gusts of up to 300 kilometres per hour (185 miles per hour), and so is causing significant destruction to property and the natural environment along hundreds of kilometres of the Queensland coastline.

Satellite image (or click for animation) of Severe Tropical Cyclone Yasi, covering 30 January through 2 February. Credit for original images to Japanese Meteorological Agency.

Flooding rains will fall along a 500 kilometre stretch of the Queensland coast, centred on Cairns, with the worst-affected areas receiving more than 300 millimetres of rain overnight Wednesday and into Thursday. More than 100 millimetres of rain will fall across inland north-central Queensland, again with the potential for severe flooding. This rain will fall on ground already saturated by heavy rains throughout December and January, leading to severe flooding in both coastal and inland areas of north-central Queensland. Yasi will remain far to the north of Brisbane, and so will not hamper the flood recovery efforts there.

Landfalling tropical cyclones in Queensland are approximately five times more likely during strong La Nina conditions, as are presently occurring, than during El Nino. La Nina refers to abnormally cool Pacific Ocean temperatures; El Nino is its opposite and results in a warmer Pacific. During La Nina, the ocean temperatures along the Australian coast warm, favouring the development of intense tropical cyclones such as Yasi. La Nina also reduces wind shear, the change in the direction and speed of the wind between the lower and upper portions of the atmosphere, which again favors tropical-cyclone development.

Tracks of tropical cyclones in Australian summer (December-February) during the last seven La Nina (left) and last seven El Nino (right) seasons, dating to 1979. The point at which the cyclone formed is marked with a circle. Cairns is marked with a cross. Figure created by Dr. Nicholas Klingaman and Mr. Andrew King from data supplied by the International Best Track Archive for Climate Stewardship.

Ongoing research at the University of Reading's Walker Institute is investigating the relationship between Australian tropical cyclones and La Nina, including the potential impacts of climate change on tropical cyclone activity, using the latest computer models of the Earth's climate. This work is part of the Walker Institute's collaboration with the Queensland Climate Change Centre of Excellence.

Information about the author

Dr. Nicholas Klingaman is a tropical climate scientist working at the University of Reading for the Walker Institute for Climate System Research and the National Centre for Atmospheric Science. He is leading the Walker Institute's collaboration with the Queensland Climate Change Centre of Excellence. The collaboration aims to understand the causes of historical variations in Queensland's rainfall, then to use that information to provide improved predictions of rainfall for the next several decades.