Winter 2023 is unlikely to be colder than average, but it will probably be colder than the winters of recent years, which were some of the warmest on record.
Niwa National Climate Centre forecasting principal scientist Chris Brandolino said that an El Nino weather pattern would continue to develop during winter, and be a potentially strong event by spring.
"Despite a trend towards El Nino, warmer-than-average sea temperatures remain present in the western Pacific.
"This is expected to continue to fuel moisture-rich disturbances in the New Zealand region through at least June, some of which will bring heavy rainfall, snow, and strong winds.
"Higher than normal air pressure is forecast to develop in the Tasman Sea during July and/or August, leading to periods of below normal rainfall, particularly in the north and east of both islands.
"Marine heatwave conditions persisting in New Zealand’s coastal waters will likely prevent a sharply colder-than-average winter, although more frequent southerly-quarter winds may cause winter 2023 to be colder than recent winters."
On the West Coast, the Southern Alps and foothills, inland Otago and Southland, temperatures were most likely to be above average, he said.
"Marine heatwave conditions remain present in coastal waters. That means the warmer-than-average seas will likely have an upward influence on air temperatures, particularly around the start of winter."
Rainfall totals, soil moisture levels and river flows are about equally likely to be near normal or above normal.
"July and/or August may feature more westerly winds, leading to spells of wetter than normal weather."
In coastal Otago, temperatures were about equally likely to be above average or near average, and rainfall totals were about equally likely to be near normal or above normal.
"Early to mid-June looks particularly unsettled, with periods of heavy rain and high elevation snow possible.
"July and/or August may feature more southwesterly-quarter winds, leading to spells of drier than normal weather."
Soil moisture levels were most likely to be near normal and river flows were equally likely to be near normal or above normal.
