Monsoon remains delayed

The Bureau of Meteorology says the “broadscale monsoon” conditions are yet to arrive.

Despite some heavy falls in the Katherine region this week, it has been a hot and humid time.

Katherine received 93.4mm in December against an average of 231mm.

The January average is 268mm.

The wettest January in record was the 732mm recorded in 1998, the year of the record flood which marks a 20 year milestone on Australia Day this year.

“Northern Australia is yet to experience broadscale monsoonal flow this wet season,” the bureau said yesterday.

“By convention, the Australian monsoon onset date occurs when the onset is observed at Darwin. Therefore, by this definition, the Australian monsoon onset has yet to occur—the last time the onset date was this late was during the 2011–12 wet season.

“One factor contributing to the delayed start of the Australian monsoon is the continuing tropical activity in the northern hemisphere.

“A late-season near-equatorial trough persists in the northern hemisphere, extending from a developing low near the Philippines to another weaker tropical low in the Bay of Bengal.

“This trough lessens the likelihood of monsoonal flow developing in the Australian region, by deflecting energy associated with cross-equatorial flow from the South China Sea.

“This flow from the South China Sea ideally would energise a southern hemisphere monsoon trough and thereby assist in initiating the northern Australian monsoon onset.

“The tropical depression near the Philippines may reach tropical cyclone strength in the next few days as it moves towards Vietnam,” the bureau said.

Some climate models also indicate an increased chance of a second tropical low developing closer to the Western Australian coast in about a week's time.

There are also indications that a monsoon trough may develop to Australia's north at this time, and in combination with deep-layer moisture from the Coral Sea, there is an increased chance of widespread rainfall affecting parts of far northern Australia.

Pacific Ocean climate patterns indicate a weak La Niña persists in the tropical Pacific. The event is expected to be short-lived, and end in the southern autumn of 2018.