Three-month outlook

Tropical rainfall and SST outlook: October to December 2008

During the October–December 2008 forecast period, a region of suppressed convection is likely to encompass the Solomon Islands, and a region extending southeast from Tuvalu to Pitcairn Island, including Tokelau, Wallis & Futuna, Samoa, the Northern Cook Islands, and most of French Polynesia (except the Austral Islands). Average–to–below or below average rainfall is expected for those countries.

Enhanced convection is expected to be centralised near Papua New Guinea, and also near Vanuatu, Eastern Kiribati, Tonga, and the Southern Cook Islands, with above average rainfall. Near–to–above average rainfall is forecast for Fiji, Niue, New Caledonia, and the Solomon Islands for the next three-month period. There is no clear precipitation forecast for the Austral Islands and the Society Islands.

SSTs are expected to be above normal in a band extending from near Papua New Guinea, southeast to Fiji, including Vanuatu, New Caledonia, and the Solomon Islands. Near – above normal SSTs are forecast for Tonga and the Southern Cook Islands. Normal to below normal SSTs are forecast for the northeastern sector of French Polynesia, including the Tuamotu archipelago and the Society Islands.

The expected to be above normal in a band extending from near Papua New Guinea, southeast to Fiji, including Vanuatu, New Caledonia, and the Solomon Islands. Near – above normal SSTs are forecast for Tonga and the Southern Cook Islands. Normal to below normal SSTs are forecast for the northeastern sector of French Polynesia, including the Tuamotu archipelago and the Society Islands.

NOTE: Rainfall estimates for Pacific Islands for the next three months are given in the table. The tercile probabilities (e.g., 20:30:50) are derived from the interpretation of several global climate models. They correspond to the odds of the observed rainfall being in the lowest (driest) one third of the rainfall distribution, the middle one third, or the highest (wettest) one third of the distribution. On the long-term average, rainfall is equally likely (33% chance) in any tercile.