NIWA Southwest Pacific Tropical Cyclone Outlook

New Zealand’s National Institute of Water & Atmospheric Research (NIWA) and New Zealand MetService have issued a tropical cyclone outlook on behalf of collaborating organisations from the southwest Pacific, including Australia, the USA, the Pacific Island National Meteorological Services, French Polynesia, and New Caledonia.

Climate and weather forecasting organisations across the Pacific are predicting near normal tropical cyclone numbers for the 2011 – 12 season as a whole. On average, ten named tropical cyclones occur in the southwest Pacific (between 135°E and 120°W) each season (November – April). The TC forecast update indicates that a total of 6 – 8 named cyclones are expected for the late season (February – April).

Two named storms have occurred since the start of the season in November 2011 through the end of January 2012 (TC Fina and TC Grant). As such, the November–April seasonal total is likely to be in the range of 8 – 10 named storms. A small area of higher than normal activity is expected to be focused well south of the Southern Cook Islands and Austral Islands. For most island groups, TC activity is expected to be normal or below normal for the remainder of the season.

Despite normal or below normal activity, most countries west of the International Date Line, including Papua New Guinea, the Solomon Islands, Vanuatu, New Caledonia, and New Zealand (from ex–tropical cyclones) are likely to experience an interaction or two with a tropical cyclone because of La Niña that is currently in place. It should be recognised that the expectation of activity (and associated risk) ascribed for each island group is subjective, but these expectations are based on the style of La Niña that exists at present, along with international climate forecast centres that indicate the high likelihood of La Niña diminishing from mid-autumn.

Note that the forecast of normal or below normal activity for islands like New Caledonia, Vanuatu, Fiji, and Tonga indicates two or three tropical cyclones can still be expected during the season as a whole. In addition, most of the tropics and sub–tropics can be severely affected by at least one tropical cyclone during the remainder of the season, and as such all nations should remain vigilant.

ENDS