Three-month outlook

The outlook for December 2002 to February 2003

The present moderate El Niño event in the tropical Pacific is expected to last through summer, but should remain weaker than the 1997-98 event. A weakening of El Niño is likely during autumn 2003.

Summer in New Zealand is expected to be influenced by a continuation of enhanced cyclonic (low atmospheric pressure) activity across southern New Zealand, accompanied by episodes of stronger than normal westerly or southwesterly winds.

Temperatures are expected to be near average in the north and east of the North Island, below average in the western South Island, and average or below average elsewhere. Below normal or normal rainfall is expected in most places, except for the west and south of the South Island where normal or above normal rainfall is expected. River flows and soil moisture levels are expected to follow a pattern similar to that for rainfall.

During El Niño conditions there is a slightly reduced risk of a tropical cyclone affecting New Zealand during the summer. The risk is usually greatest in the late summer and early autumn.

A. Climate models give no strong signals about how the climate will evolve, so we assume that there is an equal chance (33%) of the climate occurring in the range of the upper, middle or lower third (tercile) of all previously observed conditions.

B. There is a relatively strong indication by the models (60% chance of occurrence) that conditions will be below average, but, given the variable nature of climate, the chance of average or above-average conditions is also shown (30% and 10% respectively).