Seasonal Climate Outlook: 2006 - January 2007

NATIONAL CLIMATE CENTRE Friday 3 November 2006

Seasonal Climate Outlook: November 2006 - January 2007

A Moderate El Niño, Early Summer Tending Dry And Cool In Some Places

A moderate El Niño event has become established in the tropical Pacific, and will influence New Zealand’s climate through the summer, according to the latest predictions from the NIWA National Climate Centre.

The Centre says people can generally plan for an average summer, though farmers in some northern and eastern areas will be preparing for dry conditions. It says normal or below normal rainfall is likely across the country except in the west and south of the South Island. Temperatures may be a little cooler than average in some regions, while normal summer temperatures should be experienced elsewhere.

The tropical cyclone season has already begun. Moderate El Niño conditions are likely to increase the chances of tropical cyclone activity for several tropical South Pacific countries over coming months. Countries with increased risk over this period include Fiji, Wallis and Futuna, Tonga, Niue, and the southern Cook Islands.

For New Zealand, the El Niño conditions will not have much effect on the likelihood of experiencing an ex-tropical cyclone. There is an 80% chance, through to April, of one passing within 500 km of the country. The north and north east of the North Island are the areas most at risk.

Overall Picture

Temperature:
Air temperatures are likely to be average or below average in all regions. The region most likely to be cooler than average is the western South Island, while temperatures are most likely to be average in the eastern North Island.
Sea surface temperatures in the New Zealand region are expected to be near or a little below normal.

Rainfall, soil moisture, and stream flows:
Rainfalls are likely to be normal or below normal in the north and east of the North Island and the east of the South Island, including Marlborough. Above normal rainfall is likely in the west of the South Island with normal rainfall elsewhere. Near- or below-normal soil moisture levels and stream flows are expected in most areas, except the west and south of the South Island, where these are likely to be normal or above normal.

Regional predictions for the next three months:

Northland, Auckland, Waikato, Bay of Plenty:
Average or below average temperatures are likely, with normal or below normal rainfall and soil moisture. Below normal streamflows are expected.

Central North Island, Taranaki, Wanganui, Manawatu and Wellington:
Average or below average temperatures are likely. Near-normal rainfall, soil moisture, and stream flows are likely.

Gisborne, Hawkes Bay, Wairarapa:
Near average seasonal temperatures are likely. Normal or below normal rainfall is likely, but soil moisture levels and stream flows are likely to be near normal.

Nelson, Marlborough, Buller:
Average temperatures are likely. Normal or below normal rainfall is likely, with Marlborough more likely to be below normal. Soil moisture levels and stream flows are likely to be normal or below normal.

West Coast, Alps and Foothills, Inland Otago, Southland:
Below average temperatures are likely. Above normal rainfall is likely, with normal or above normal soil moisture and streamflows.

Coastal Canterbury, East Otago:
Average or below average temperatures are likely. Normal or below normal rainfall is likely, with below normal soil moisture and stream flows.

Background

Climate and Oceans:
Local circulation patterns for November 2006 – January 2007 are likely to favour stronger than average south-westerly airflow over the country, with below average pressures to the southeast of New Zealand.

Sea surface temperatures are above average across the equatorial Pacific, around +1°C above average from the Date Line to South America. A moderate El Niño event is now established in the tropical Pacific. The El Niño will influence on New Zealand climate through summer 2006/07. Consistent with this, predicted circulation patterns favour lower than average pressures to the south east of the South Island, with more southwesterly winds than usual over New Zealand.

Ends

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