STOCK IMAGE
Temperatures for Northland, Auckland, Waikato, Bay of Plenty were expected to be above average (70% chance) in the NIWA January/March climate summary.
More sub-tropical winds and marine heatwave conditions were expected to result in above average overnight temperatures and higher humidity in particular.
Rainfall totals were equally likely to be near normal (40% chance) or above normal (35% chance). Sub-tropical low pressure systems and/or atmospheric rivers were forecast to move south into the region with some regularity, such as during early January, which would increase the risk for occasional heavy rainfall and flooding.
Rainfall was most likely to be above normal in the east of the North Island, below normal in the west of the South Island, near normal in the west of the North Island, and about equally likely to be near normal or above normal across the remainder of the country.
Air pressure was forecast to be higher than normal over and to the south of the South Island and lower than normal north of the country. The high pressure was expected to be associated with an easterly quarter air flow anomaly for the season as a whole.
La Niña continued during December and a marine heatwave intensified in Aotearoa New Zealand’s coastal waters with sea surface temperatures (SSTs) 1.1˚C to 1.8˚C above average.
Warmer than average regional seas were expected to fuel occasional heavy rainfall, such as during early January; however, dry spells were expected during periods of high pressure, particularly about inland and western parts of both islands. A dry spell was possible in the mid-to-late January period. The risk for dryness is elevated for Otago, Southland, and West Coast.
La Niña was expected to ease to neutral by early autumn.
The risk for tropical cyclones in the Southwest Pacific during January was medium, though the risk for ex tropical cyclone activity through to April is normal to elevated. As we have seen, these systems can cause flooding rainfall, strong winds, and coastal hazards.
Soil moisture levels were most likely to be near normal in all regions. River flows were equally likely to be near normal or below normal in the west of the South Island, about equally likely to be near normal or above normal in the east of the North Island and north of the South Island, and most likely to be near normal in all other regions.
