Tropical cyclones have always been a source of fascination for many people as well as playing a vital role in summer rainfall trends right across Australia. So what does the 2009-10 cyclone season have in store? TCs are complicated beasts and need conditions to be just right to start. Some of these conditions include: + a pre-existing low pressure system + sea surface temperatures greater than about 26 degrees + a deep layer of moisture through the atmosphere Such conditions are really only satisfied in tropical parts of the world. But this season another factor comes into play: the El Nino. In El Nino conditions, eastern parts of the Pacific Ocean may have cooler waters than usual, and the winds that bring in atmospheric moisture tend to be weak. All this combines to bring about a much less chance of Tropical Cyclones for QLD and the NT. Australian cyclones form most often in the region of ocean north of the WA Pilbara coast. The current El Nino pattern has most affect on QLD so it is likely that this season will be average for WA. The good news about this is that with a near-average season for WA ahead, SA and VIC may still be on the receiving end of vital rainfall.