Cyclones forecast for rest of summer

Cyclone Pam damage on the Tutukaka Coast. Photo / John Stone

Northland will be forced to juggle between a strong El Nino weather pattern and intermittent rain - heavy at times over short periods - as a result of tropical cyclones in the Pacific.

The seasonal climate outlook for January to March, released by the National Institute for Water and Atmospheric Research (Niwa), said temperatures were most likely to be above average for the east of the North Island. Temperatures are about equally likely to be near average or above average for the other regions.

Soil moisture levels across the North Island have increased significantly to normal or above normal when compared to this time last week for eastern Northland, Auckland and Waikato. NIWA principal climate scientist, Chris Brandolino, said tropical cyclones coming down from the north of New Zealand were likely to disrupt a long dry spell in Northland.

"The tropical cyclones near and east of the dateline could be a silver lining for Northland and could come 500km of either north or east of the country.

"There's a lot of uncertainty but we're of the opinion that over the next three months, the likelihood of rain in Northland is lower than normal but it doesn't mean you won't have a downpour or have rainy days," he said.

Mr Brandolino said torrential rain over a short period of time could result in flash flooding which wouldn't be beneficial for Northland.

Cyclones Lusi and Ita struck Northland in March and April 2015, with heavy rain and winds of up to 120km/h. It caused more than $150,000 in repair bills in the Far North. Cyclone Pam last year caused similar damage.

The NIWA climate outlook said several indicators showed a weakening of the strong westerly wind in the past two weeks, raising the possibility El Nino could have reached its peak in 2015.

"However, the current event is expected to remain in the strong category for the next three months, and the impacts of El Nino on New Zealand's climate will likely persist into autumn," it said.

International guidelines, it said, indicated that El Nino would continue from January to March then rapidly decay thereafter, with a return to normal conditions or a transition to La Nina from July to September this year. La Nina is a climate pattern associated with cooler than normal water temperatures in the Equatorial Pacific Ocean, unlike El Nino, which is associated with warmer than normal water. For Northland between January and March, rainfall is likely to be near or below normal. Soil moisture and river flow levels are most likely to be below normal.