NIWA: Mild Start To Winter

NATIONAL CLIMATE CENTRE Draft for Thursday 3 May 2007

Seasonal Climate Outlook: May – July 2007

MILD START TO WINTER – SLIGHTLY DRY IN THE EAST

Temperatures are likely to be milder than average for early winter (May–July), according to the latest predictions from the NIWA National Climate Centre. Indications are that conditions in the east are expected to be slightly drier than normal.

The tropical Pacific is currently in a ‘neutral’ state, but the Centre says that there is a relatively high (50%) probability of La Niña conditions developing during the next 3 months. These conditions usually bring warmer than normal temperatures to New Zealand.

Overall Picture

Temperature:
Air temperatures are expected to be above average in most regions, and near or above average in the north of the North Island. Sea surface temperatures are expected to trend above average average in the New Zealand region for the coming three months.

Rainfall, soil moisture, and stream flows:
Normal or below normal rainfall is likely in the east of both islands, with near normal rainfalls in other regions. Below normal soil moisture and stream flows very likely in the east of the South Island. Soil moisture and stream flows are expected to be normal or below normal in the east of the North Island, and the north, west and south of the South Island. Elsewhere, normal soil moisture and stream flows are likely.

Regional predictions for the next three months:

Northland, Auckland, Waikato, Bay of Plenty:
Average or above average temperatures are likely. Normal rainfall, soil moisture and streamflows are likely.

Central North Island, Taranaki, Wanganui, Manawatu and Wellington:
Above average temperatures are likely. Normal rainfall, soil moisture, and stream flows are likely.

Gisborne, Hawkes Bay, Wairarapa:
Above average temperatures are likely, with normal or below normal rainfall and stream flows. Below normal soil moisture is expected.

Nelson, Marlborough, Buller:
Above average temperatures are likely. Normal rainfall and soil moisture levels are likely, with normal or below normal stream flows.

West Coast, Alps and Foothills, Inland Otago, Southland:
Above average temperatures are likely. Normal rainfall and soil moisture is expected. Normal or below normal streamflows are likely.

Coastal Canterbury, East Otago:
Above average temperatures are likely. Below normal rainfall is likely, with below normal soil moisture and streamflows very likely.

Background

Climate and Oceans:
Over the May to July period, pressures are expected to be higher than average south of the South Island.

Conditions are currently neutral in the tropical Pacific, but there is a relatively high (50%) probability of a transition to La Niña conditions during the next three months. The dynamical models of ENSO (El Niño Southern Oscillation) show a transition to La Niña conditions over the next 3 months, with this persisting for the remainder of the year, whilst the statistical models project neutral ENSO states for the next 6-9 months. No model retains El Niño conditions during the remainder of the year.

The pattern of sea surface temperature (SSTs) anomalies in the tropical Pacific are beginning to resemble La Niña conditions with colder than average waters in the far eastern Pacific and slightly warmer than average waters in the western Pacific. The upper-ocean heat content remains below average across the central and eastern equatorial Pacific. In the Tasman Sea, New Zealand area sea surface temperatures are slightly above normal.

ENDS

© Scoop Media