SW Pacific TC Guidance for the 2011 -12 Season

Below normal tropical cyclone (TC) activity is likely formost islands west of the International Date Line in the southwest Pacific during the November 2011 – April 2012 season, with normal or slightly elevated activity near the Gulf of Carpentaria and North Queensland, particularly late in the season. 

Below normal tropical cyclone (TC) activity is likely formost islands west of the International Date Line in the southwest Pacific during the November 2011 – April 2012 season, with normal or slightly elevated activity near the Gulf of Carpentaria and North Queensland, particularly late in the season. Tropical cyclone activity is likely to be near normal to the east of the International Date Line. Although reduced activity west of the International Date Line is likely, all communities should remain alert and prepared.

On average, nine tropical cyclones occur each year for the southwest Pacific, and are grouped into classes ranging from 1 to 5, with 5 being the most dangerous. For the coming season, at least one cyclone is forecast to reach at least Category 3, with mean wind speeds of at least 64 knots or 118 km/h and one system may reach at least Category 4 strength, with mean wind speeds of at least 86 knots or 159 km/h. The ICU forecast indicates 5 – 8 named TCs are likely for the upcoming season.

Places like Vanuatu and New Caledonia typically experience the greatest TC activity, with an average of about 3 or 4 TCs passing close to those countries each year (see Table, right). Near normal to slightly increased TC activity for the 2011–12 season is likely over North Queensland, but lower than normal activity is indicated for most other regions to the west of the Dateline.

Historical cyclone tracks indicate that TCs can affect parts of southwest French Polynesia, including the Society and Austral Islands, and the southern Cook Islands during La Niñas, especially late in the season. The Austral Islands and Society Islands are likely to experience slightly increased activity this year, particularly during the latter half of the TC season.

All islands should remain vigilant as the current La Niña continues to evolve with progression into summer. More details about this forecast and the science underpinning it can be found at http://www.niwa.co.nz/node/103022. In the PacificIslands, consult with your local meteorological service for tropical cyclone guidance as the season progresses.