NIWA seasonal climate outlook: February – April 2010

autumnNIWA has published its climate outlook for the next three months:

“A cool end to summer, and continuing drier than normal in the north”

The current El Niño will continue, but is likely to weaken in autumn, meaning that temperatures are likely to stay on the cool side, and dry conditions to persist in the very north of NZ.

From NIWA:

The centre’s latest outlook states that on average over the three months February-April, mean sea level pressures are likely to be higher than normal to the north of the country, associated with slightly stronger than normal westerlies over New Zealand.

Current drier than normal soil conditions are likely to continue in the north of the North Island, and are likely to prevail in the east of the North Island, where below normal stream flows and soil moisture levels are likely through to April.

The centre says February to April rainfall totals are likely to be in the normal or below normal range in the north and east of the North Island and in Marlborough, normal or above normal in the western South Island, and in the normal range in other regions.

Temperatures are likely to be near average or below average in all regions, over the three months of February to April as a whole. There will still be variability, with some warm spells at times, especially in eastern regions in north-westerly wind conditions.

River flows and soil moistures are likely to be near normal or below normal in the North Island, near normal in the north and east of the South Island, and normal or above normal in the western South Island.

Overall Picture

Temperature:

Air temperatures are likely to be average or below average everywhere. Sea surface temperatures are expected to remain below average around and east of the South Island, and near average to the north of New Zealand.

Rainfall, soil moisture, and stream flows:

Rainfall is likely to be normal or below normal over the north and east of the North Island and in Marlborough, normal or above normal in the west and south of the South Island, and near normal elsewhere. Rivers flows and soil moistures are likely to be near normal or below normal in the North Island, near normal in the north and east of the South Island, and normal or above normal in the west and south of the South Island.

Regional predictions for the next 3 months:

Northland, Auckland, Waikato, Bay of Plenty:

Temperatures are equally likely to be in the near average or below average category.  Seasonal rainfall totals are equally likely to be near normal or below normal, while river flows and soil moisture levels are very likely to be in the below normal range.

Central North Island, Taranaki, Wanganui, Manawatu and Wellington

Seasonal temperatures are likely to be in the average or below average category. Rainfall totals are likely to be near normal, while stream flows and soil moisture levels are likely to be near normal or below normal, for the three months as a whole.

Gisborne, Hawke’s Bay, Wairarapa:

Temperatures averaged over the three months are equally likely to be in the near average or below average category. Seasonal rainfall totals, stream flows and soil moisture levels are likely to be below normal.

Nelson, Marlborough, Buller:

Seasonal temperatures are likely to be below average. Rainfalls, stream flows and soil moisture levels are likely to be normal over all, but with below normal rainfalls more likely in the east of the region.

West Coast, Alps and Foothills, Inland Otago, Southland:

Temperatures are likely to be in the average or below average category. Seasonal rainfall, stream flows and soil moisture levels are equally likely to be near normal or above normal.

Coastal Canterbury, East Otago:

Temperatures are most likely to be in the near average category, averaged over February-April. Seasonal rainfall totals, soil moisture levels and stream flows are all likely to be in the normal range.

Background

The El Niño continues at moderate strength in the Tropical Pacific, and exhibits many features of a mature event. As often occurs, the El Niño is expected to weaken towards neutral conditions through the autumn.

El Niño events can often lead to dry conditions in eastern and northern parts of New Zealand over the summer season. Soil moistures are very low in Northland, and in some parts of the Bay of Plenty, and eastern south Canterbury and Otago. The latest outlook suggests that drier conditions are likely in the north and east of the North Island on average through to April. El Niño events are also often associated with cooler than average conditions in the New Zealand region, consistent with the latest outlook.