Weather: Cyclone Liua forms in Pacific, leftovers could reach NZ

A rare, out of season tropical cyclone has formed in the Southwest Pacific - and an expert has issued a warning for New Zealand.

Tropical Cyclone Liua is growing in strength near the southern Soloman Islands, although Fiji MetService says it is likely to remain Category 1.

NIWA has revealed this is the first tropical cyclone to form in September in the Southwest Pacific since 1950 - or in 68 years.

Weather Watch head forecaster Philip Duncan says it could be an ominous sign for summer.

"Often we see tropical storms still forming after a cyclone season has officially ended as sea surface temperatures after summer can take several weeks to cool down," he says.

"However we have literally just passed the point where sea temperatures in the Southern Hemisphere should be at their coolest.

"To see a cyclone form so early in the season may be an indicator of bigger storms to come this summer."

Cyclone Liua is expected to move south-southwest into the Coral Sea over the coming days.

MetService says it won't affect New Zealand, but Weather Watch says its effects could reach our shores.

"This storm will weaken in the coming days and fall apart however all the energy left behind from Liua will remain," Mr Duncan says.

"There is a chance that in one week from now the remnants of this tropical storm will reach northern New Zealand as a new low. It is not locked in but one to keep an eye on."