Tropical rainfall and SST outlook: November 2008 to January 2009
During the November 2008–January 2009 forecast period, a region of suppressed convection is likely to encompass the central and eastern Southwest Pacific, in a region extending from Western Kiribati to the Marquesas Islands and the Society Islands, including Tuvalu, Tokelau, Wallis & Futuna, Samoa, the Northern Cook Islands, and the Tuamotu archipelago. Below normal or near–to–below normal rainfall is expected for those countries.
Enhanced convection is expected to be focused near Papua New Guinea, and also near Vanuatu, New Caledonia, Tonga, Fiji, and Niue with above average rainfall. Near–to–above average rainfall is forecast for the Southern Cook Islands, the Austral Islands, and Pitcairn Island for the next three-month period. No clear precipitation forecast is offered for the Solomon 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 Niue, the Southern Cook Islands, the Austral Islands and Pitcairn Island. Normal to below normal SSTs are forecast for the northeastern sector of French Polynesia, including the Tuamotu archipelago and the Society Islands, Tuvalu, Tokelau, and both Eastern and Western Kiribati.
The confidence in the forecast model skill for this seasonal rainfall outlook is moderately high for most Pacific Island countries. In the past, the average region-wide hit rate for forecasts issued in November is 64%, 4% higher than the long-term average for all months combined. The SST forecast confidence is moderate for this period.
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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.