'Typical' tropical cyclone season expected

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Bureau of Meteorology expects an average season with 10 to 13 cyclones.

In its latest severe weather outlook for 2017/18, the Bureau of Meteorology (BOM) is predicting a “typical” number of cyclones to hit our shores in the upcoming cyclone season from November through to April 2018.

According to BOM, on average there are 10 to 13 tropical cyclones each season in the Australian region, four of which typically cross the coast. At least one tropical cyclone has crossed the Australian coast each season since reliable records began in the 1970s.

BOM's outlook is based on the status of the El Niño–Southern Oscillation (ENSO) over the preceding July to September. These indicators suggest ENSO-neutral to weak La Niña-like conditions in the tropical Pacific Ocean and slightly warmer-than-average ocean temperatures to the north and east of Australia which marginally increase the likelihood of cyclones developing.

Overall, BOM says there is a 56% chance of more cyclones than average in the Australian region over the coming season; conversely, there is a 44% chance of having fewer tropical cyclones than average. If there is a shift towards a La Niña, the chance of more tropical cyclone activity will increase.

During ENSO-neutral years, the first tropical cyclone to make landfall over Australia typically occurs in late December. In La Niña years, the first cyclone landfall typically occurs earlier, around the first week of December.

However, BOM also warns that it is rare for tropical cyclones to be spread evenly across the season. Last year saw only one cyclone form before mid-February, a late start to the season, but this was followed another eight cyclones before the end of April.

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