El Nino may linger until May

A report found rainfall levels over the next three months would likely be "below normal" Photo / Duncan Brown

A severe El Nino playing with our climate could linger until May, a new climate outlook has found.

The National Institute of Water and Atmosphere's latest report, out today, found rainfall levels over the next three months would likely be "below normal" in the north and east of the North Island.

There was a 100 per cent probability that the El Nino system present over the past few months would continue until the end of February - and models have the event hanging around into the March to May period.

By some measures, the current event was on par with the 1997/98 El Nino - the strongest since 1950 and the cause of intense droughts that cost New Zealand hundreds of millions of dollars.

By next winter, however, models predicted the climate would have made a rapid return to ENSO-neutral conditions.

In New Zealand, the ocean-driven system typically brings cooler, wetter conditions, bringing higher rainfall to regions that are normally wet, and often drought to areas that are usually dry.

Farmers in the western, wetter parts of the country often faced significant damage to pastures from too much rainfall, and it was also harder for stock to thrive in the constant wet.

Those in the east, faced with dry conditions, needed to consider food availability for stock.

The Niwa outlook forecast above-normal pressure to the north of New Zealand, with below normal pressure to the south of the country.

This circulation pattern was likely to be accompanied by anomalous westerly wind flows - a signature of El Nino conditions.

From here until February, temperatures were most likely to be near average for the north and east of the North Island as well as the east of the South Island, and about equally likely to be near average or below average everywhere else.

Away from the dry areas in the north, seasonal rainfall totals were about equally likely to be near or below normal for the west of the North Island as well as the north and east of the South Island, and equally likely to be near or above normal for the west of the South Island.

Soil moisture levels were about equally likely to be normal or below normal in all regions of the North Island as well as the east of the South Island. "Above normal" soil moisture levels were most likely for the west of the South Island and below normal soil moisture levels are most likely for the north of the South Island.

River flows were equally likely to be normal or below normal in the north and west of the North Island, most likely to be below normal in the east of the North Island and the north and east of the south Island, and most likely to be above normal in the west of the South Island.

In Northland, Auckland, Waikato and Bay of Plenty, temperatures were most likely to be near average, rainfall totals were most likely to be below normal, soil moisture levels were equally likely to be near normal or below normal and river flows were about equally likely to be near normal or below normal.