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Sluggish cyclones add to flood damage

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Experts say tropical cyclones are taking longer to move, doubling rainfall and flooding in the locations they hit.

A study by the US National Centres for Environmental Information shows cyclones may have slowed as much as 10% on global average speeds between 1949 and 2016.

Change has occurred in every ocean basin except the northern Indian Ocean.

The greatest shift is in the northern Pacific Ocean, where cyclones have slowed by up to 20%, followed by the seas around Australia at 15%.

Over land in Australia, tropical cyclones have slowed by up to 19%. The figure is 30% in the western north Pacific and 20% in the Atlantic.

Report author Jim Kossin says the trends are almost certainly increasing rainfall figures and flooding.

Hurricane Harvey, which stalled over land, dumped more than 1.27 metres of rain over Houston, Texas in five days.

Atmospheric circulation that drives cyclone movement is expected to weaken, the report says.