The evidence for a developing El Niño event, which is expected to influence New Zealand climate over spring and summer 2002-03, continues to strengthen, though the magnitude of the coming event remains uncertain.
El Niño is typically associated with below average temperatures in many places. However, the outlook for July to September 2002 is for normal or above normal temperatures in all regions because of the influence of local sea temperatures and a warm Indian Ocean. Short-term cold outbreaks typical of winter are still likely, even though average temperatures are expected to remain relatively high.
Rainfall is expected to be near normal in many regions, but may be above normal in the north of the North Island and the west of the South Island, and below normal in eastern South Island regions.
Normal soil moisture levels and river flows are predicted for all regions of the country, except for the north of the North Island and the west of the South Island where above normal to normal soil moisture levels and river flows are likely.
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).