El Niño conditions are expected to last through summer 2002-03, but it is likely to be a much weaker event than that of 1997-98. Stronger than normal westerly winds are predicted during late spring.
Over most of the country, temperatures are expected to be average to above average. However, above average temperatures are likely in the eastern North Island, and below average temperatures are possible in the western South Island.
Near normal rainfall is expected for the North Island, except for the east where falls are expected to be below normal. For the South Island, there is a tendency towards above normal rainfall in the west, and below normal rainfall in the east.
Below normal soil moisture levels and river flows are predicted for the east coasts of both islands, with lower river flows also likely in the north of the North Island. Above normal soil moisture levels and river flows are likely in the west and south of the South Island.
The tropical cyclone season usually begins in November: El Niño conditions imply a slightly reduced risk of a tropical cyclone affecting New Zealand during this summer.
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).