There are now strong indications that an El Niño may develop by spring. One indication is that sea surface temperatures in the equatorial Pacific are now above normal, and are expected to rise further relative to normal over coming months. Another typical feature of El Niño, lower than normal sea surface temperatures to the west of New Zealand, is also becoming evident.
Rainfall is expected to be near normal in most regions of New Zealand, apart from below normal in the east of the North Island and normal to below normal in the east of the South Island.
Temperatures are expected to be normal or above in the north and west of the North Island, above normal in the west of the South Island, and normal in other regions.
Normal soil moisture levels and river flows are predicted for most regions of the country. Below normal river flows and normal to below normal soil moisture levels are likely in the east of the South Island. In the east of the North Island, both soil moisture levels and river flows are likely to be below normal.
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).