NIWA seasonal climate outlook: November 2009 – January 2010

pohutukawa smallNIWA has published its climate outlook for the next three months:

“Moderate El Niño conditions, but muted influence on New Zealand in the coming season”

It seems that a moderate El Niño is in force, and is likely to persist over summer, although it is unlikely to have much of an effect on New Zealand’s climate.

Most climate indicators expected to be at normal, or slightly below normal, levels.

Overall Picture

Temperature:

Air temperatures are likely to be near average over the North Island and northern South Island, and average or below average over the rest of the South Island. Sea surface temperatures near New Zealand are expected to be somewhat below average during November-January.

Rainfall, soil moisture, and stream flows:

Rainfall is likely to be normal or below normal in the north and east of the North Island, and near normal elsewhere. Rivers flows and soil moisture are likely to be normal or below normal in all regions.

Regional predictions for the next three months:

Northland, Auckland, Waikato, Bay of Plenty:

Temperatures are likely to be in the near average category. Seasonal (3-month) rainfall totals, soil moisture levels and stream flows are expected to be in the normal or below normal range.

Probabilities are assigned in three categories; above average, near average, and below average.

Central North Island, Taranaki, Wanganui, Manawatu and Wellington:

Seasonal temperatures are projected to be in the near average category. Three-month rainfall totals, soil moisture levels and stream flows, are expected to be near normal.

Probabilities are assigned in three categories; above average, near average, and below average.

Gisborne, Hawke’s Bay, Wairarapa:

Three-month temperatures are likely to be in the near average category. Seasonal rainfall totals, soil moisture levels, and stream flows are expected to be in the normal or below normal range.

Probabilities are assigned in three categories; above normal, near normal, and below normal.

Nelson, Marlborough, Buller:

Temperatures are likely to be in the near average category. November-January rainfall, soil moisture levels and stream flows are likely to be in the normal range.

Probabilities are assigned in three categories; above average, near average, and below average.

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

Temperatures are likely to be in the below average category. Seasonal rainfall, soil moisture levels and stream flows are projected to be in the normal range.

Probabilities are assigned in three categories; above average, near average, and below average.

Coastal Canterbury, East Otago:

Temperatures are equally likely to be in the near average or below average categories. Seasonal rainfall is expected to be in the normal range, while soil moisture levels and stream flows are likely to be normal or below normal overall.

Probabilities are assigned in three categories; above average, near average, and below average.

Background

A moderate El Niño is present in the equatorial Pacific Ocean, and is expected to persist through to the autumn of 2010. Most of the El Niño forecast models predict El Niño persisting to the end of summer, with some strengthening a little between now and the end of the year.

El Niño events can lead to dry conditions in eastern parts of New Zealand over the spring and summer seasons. Consistent with this picture, the latest guidance suggests that November 2009-January 2010 rainfall is likely to be in the normal or below normal range for the north and east of the North Island.