Forecasting principal scientist Chris Brandolino said for the next three-month period as a whole, the atmospheric circulation pattern over New Zealand was expected to bring abnormal high-pressure systems to the south of the country, and abnormal low-pressure systems to the north, leading to unusual weather flows from the east.
He said weak La Nina conditions were persisting in the tropical Pacific, but were on a weakening trend.
This weakening was expected to accelerate in the coming months, and there was about an 80% chance for El Nino-Southern Oscillation-neutral conditions (neither El Nino nor La Nina) returning by the end of April.
"Slow-moving high-pressure systems early in February should bring periods of traditional summer conditions to many parts of the country, interrupted by some shorter unsettled spells," he said.
Further settled conditions might occur in March, he said.
"A dramatic pattern change is not anticipated in April, with rainfall events most likely to come from the north, contrasting with high-pressure systems still bringing periods of settled conditions."
On the West Coast, the Southern Alps and foothills, inland Otago and in Southland, temperatures were equally likely to be above average or near average.
Rainfall totals in those areas were about equally likely to be near normal or below normal; soil moisture levels were most likely to be near normal, and river flows were equally likely to be below normal or near normal, he said.
Along coastal Otago, temperatures were most likely to be near average, while rainfall totals, soil moisture levels and river flows were about equally likely to be above normal or near normal.
Looking further ahead, global climate models favoured the development of El Nino conditions in the eastern tropical Pacific later in 2026, he said.
El Nino brings stronger westerlies and drier conditions in eastern New Zealand, and wetter conditions in the west.
"It is important to note that there are fundamental physical limitations to the predictability of future El Nino-Southern Oscillation states at this time of year — the so-called ‘predictability barrier’.
"However, the strength and location of sub-surface ocean temperature anomalies is causing a higher-than-normal degree of confidence in a forecast for El Nino developing later in 2026," he said.
