NIWA has published its climate outlook for the next three months:
“Mild conditions likely to continue through winter”
NIWA’s National Climate Centre expects that winter mean temperatures are likely to be above average across most of the country, with some short-term cold snaps and frosty periods.
In addition, El Niño has dissipated, and a La Niña could develop by early spring.
Near normal rainfall is expected in most places (bar the southwest of the North Island, which might experience normal or below-average rainfall).
In terms of soil moisture and stream flows, near normal levels are expected in the north and west of the North Island, and near-normal conditions elsewhere.
Finally, mean sea level pressures are likely to be higher than normal over the North Island, associated with somewhat stronger than normal westerlies over the South Island.
Overall Picture
Temperature:
Winter temperatures are likely to be above average over most of the country, but average or above average in the east of the South Island. Despite the likelihood of a milder than normal winter, typical winter cold spells and frosts are still expected at times. Sea surface temperatures are expected to be near average around New Zealand over the winter period.
Rainfall, soil moisture, and stream flows:
Rainfall is likely to be near normal over most of the country, but normal or below normal in the southwest of the North Island. Normal or below normal soil moisture levels and stream flows are likely in the north and west of the North Island, but over the rest of New Zealand near-normal conditions are the most likely outcome.
Regional predictions for the next three months:
Northland, Auckland, Waikato, Bay of Plenty:
Temperatures are likely to be above average. Seasonal rainfall totals are likely to be near normal, while soil moisture levels and stream flows are equally likely to be near normal or below normal.
Central North Island, Taranaki, Wanganui, Manawatu and Wellington:
Above average seasonal temperatures are likely. Rainfall totals are equally likely to be near normal or below normal, while stream flows and soil moisture levels are equally likely to be in the near normal or below normal range, for the three months as a whole.
Gisborne, Hawke’s Bay, Wairarapa:
Temperatures averaged over the three months are likely to be in the above average category. Seasonal rainfall totals, stream flows and soil moisture levels, are all likely to be in the normal range.
Nelson, Marlborough, Buller:
Seasonal temperatures are likely to be in the above average range. Rainfalls, stream flows and soil moisture levels are likely to be near normal overall.
West Coast, Alps and Foothills, Inland Otago, Southland:
Temperatures are likely to be in the above average category. Seasonal rainfall, stream flows and soil moisture levels are likely to be near normal.
Coastal Canterbury, East Otago:
Temperatures are equally likely to be in the average or the above average category, on the whole during winter. Seasonal rainfall totals, soil moisture levels and stream flows are likely to be in the normal range.
Background
The El Niño conditions that prevailed since winter 2009 have dissipated, and the equatorial Pacific is now in a neutral state. Recent trends suggest a La Niña could develop by early spring.