The moderate El Niño event in the tropical Pacific is expected to last through summer 2002-03, but is unlikely to be as strong as the 1997-98 event. Early summer climate in New Zealand is expected to be influenced by a continuation of lower than normal atmospheric pressures across southern New Zealand and episodes of stronger than normal westerly winds.
Temperatures are expected to be near average over the North Island and northern South Island, tending to below average over the rest of the South Island. Below normal or normal rainfall is expected in Marlborough, Canterbury, Otago, and the east and north of the North Island. Above normal rainfall is possible in the west and south of the South Island.
Soil moisture is expected to be below normal in Nelson and Marlborough, normal or below normal across eastern parts of both islands, and normal elsewhere. Below normal streamflows are predicted for all regions except for the west coasts of both islands and in Southland, where normal flows are predicted.
The presence of El Niño during the coming summer slightly reduces the tropical cyclone risk over New Zealand.
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).