Cyclone Cempaka is currently south of the Indonesian island of Java and forecasters expect it will reach the far western coast of Western Australia.

“Cempaka is embedded in a weak tropical trough which extends to a second tropical low further to its west,” a Bureau of Meteorology spokesman said.

“This second low is forecast to merge with Cempaka and slowly strengthen as it moves in a southerly direction.

“Current forecasts suggest this system may track towards the far western coast of Western Australia at tropical cyclone strength, but is unlikely to make landfall at tropical cyclone intensity.”

Cempaka will be the first tropical cyclone in the southern hemisphere for the 2017-18 season.

Katherine has already had a wet November.

A total of 155.8mm has already been recorded against an average 93mm and most of the local rivers are running strongly again.

Tropical cyclone Cempaka was named by the Indonesian meteorological agency.

As well the bureau said a monsoon trough was developing in the southern hemisphere.

The bureau spokesman said Cempaka is embedded in a distinct low-pressure trough in the near-equatorial region of the southern hemisphere, readily seen on recent weather charts.

“The trough in the southern hemisphere is the southern component of the twin near-equatorial trough set up which is apparent either side of the equator. This is a typical transitional weather pattern seen at this of the year when neither a northern or southern hemispheric monsoon flow is prevalent.

“While there are some monsoonal characteristics in this southern hemisphere trough, including some wind flow feeding into it from the northern hemisphere, it is currently a relatively weak feature. However, there are some broadscale factors which may invigorate and strengthen the trough in the coming week.”

“The tropical cyclone activity forecast in the region may assist in dragging any monsoon trough further south, but models currently indicate the monsoon trough is unlikely to initiate monsoon onset for northern Australia in the next week or two.”