The 2010/11 tropical cyclone (TC) season is not only expected to be more active across northern Australia, but an earlier TC crossing in November is also likely.
The Bureau of Meteorology has released a statement outlining predictions for 20-22 TC's this season but it's important to note that this is the long term average in the Australian area of responsibility covering 90E to 160E, waters thousands of kilometres away from our mainland. But for actual waters that affect the Australian mainland (105E to 160E), the number should be closer to 15. This number is typical of La Nina years (more details on La Nina below) which usually result in above average TC activity. The long term average of TC's in the Australian area of responsibility is 12, while for Australian waters it is 10. Therefore, tropical cyclone activity in Australian waters this season is expected to be about 50% higher than the long term average. Of the TC's that are expected to develop in Australian waters this season, around half or just over half may cross the coast.
Not only this, the TC season is predicted to start a little earlier than usual, during November or early December.
The primary reason for increased TC activity is a well established La Nina in the Pacific Ocean. Under La Nina conditions, we get above average sea surface temperatures off the northern Australian coastline. This not only leads to above average rainfall and an increased risk of flooding in northern and eastern Australia (which we've already observed), but also favourable conditions for enhanced TC activity.
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