Temperatures, rainfall and soil moisture levels will be near or below normal in the Bay of Plenty this autumn, according to NIWA's outlook data.

Temperatures are considered to have a 45 per cent chance of being near average. Rainfall totals are considered to have a 40 per cent chance of being near or below normal. And soil moisture levels and river flows are given a 55 per cent chance of being below normal.

The outlook for March to May covers Northland, Auckland, Waikato, along with the Bay of Plenty.

From March to May, temperatures are most likely to be near average for all regions nationwide. But as autumn progresses, cold snaps and frosts can be expected from time to time in some parts of the country.

During the same period, rainfall is likely to be near normal or below normal for the north and west of the North Island, and for the north, west and south of the South Island.

For eastern regions on both Islands, three-month rainfall totals are most likely to be in the near-normal range.

Sea surface temperatures are expected to be near average for the coming three months around New Zealand too.

During March to May, mean sea level pressures are expected to be lower than normal to the north of the country, with higher pressures than normal to the southeast of NZ.

This circulation pattern is likely to be associated with anomalous north-easterly flows over the North Island and anomalous weak easterly flows over the South Island.

Sea surface temperatures are expected to be near average nationwide for next three months.

The equatorial Pacific Ocean continued in a neutral ENSO-state (neither El Niño nor La Niña) in February 2014.

International guidance indicates ENSO-neutral conditions are the most likely outcome for autumn, but in the following winter season about half of the international models develop El Niño or borderline El Niño conditions.

Outlook Summary

The equatorial Pacific Ocean continued in a neutral, neither El Niño nor La Niña in February. Colder than normal sea surface temperatures appeared in the eastern equatorial Pacific, but at 150m sub-surface depths an extensive region of warmer-than-normal water developed during the month.

The NIWA Southern Oscillation Index for February is -0.1, estimated at February 26. This brings the three-month December-February value to +0.4.

International guidance indicates the tropical Pacific Ocean is very likely – greater than 80 per cent chance – to remain neutral during March-May. But about half of the international models develop El Niño or borderline El Niño conditions during winter, with the other half remaining near neutral.

A similar situation persists into the spring of 2014, with about 50:50 chances of neutral or El Niño conditions.

The monthly sea surface temperature anomaly for New Zealand was approximately +0.1°C last month. While this is the 14th consecutive month SSTs have been warmer than normal around New Zealand, there has been rapid cooling of surrounding waters from +1.0°C in last December, particularly to the northwest of the North Island.

Sea surface temperatures are expected to be near average for the coming three months around New Zealand.