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La Nina brings back tropical cyclone risk

Published: 1:26PM Friday January 09, 2009 Source: NZPA

The La Nina state in the tropical Pacific is likely to bring fewer cyclones in the region between January and May, National Institute of Water and Atmospheric Research (Niwa) says.

However, there is always a risk of tropical cyclones across the South Pacific requiring preparedness for disaster prevention and mitigation, says Niwa's principal climate scientist, Jim Salinger.

For the remainder of the tropical cyclone season, from January to May 2009, more cyclones are likely for those areas of the South Pacific west of the Date Line, Salinger says.

These countries included Vanuatu, Solomon Islands and northern New Zealand.

However, fewer cyclones are likely in parts of the South Pacific east of the Date Line, such as Samoa, Tonga and Niue.

"The risk of occurrence is slightly increased for New Caledonia."

Salinger says climate forecasting organisations in the Pacific agree that La Nina conditions have redeveloped in the tropical Pacific and are expected to prevail into autumn.

"This brings about an increased normal risk of tropical cyclones in the Coral Sea."

"On average, six or seven tropical cyclones can be expected over the entire Southwest Pacific region during a weak La Nina season."

For New Zealand, the weak La Nina conditions will not have much effect on the chances of experiencing an ex-tropical cyclone, he says.

There is a slightly higher than average chance of an ex-tropical cyclone passing within 500km of the country between January and May, with the highest risk districts being Northland and Gisborne.

The ex-tropical cyclones could still cause strong winds and heavy rainfall, the most common months affecting New Zealand being January to March.