During October – December 2009, a region of suppressed convection is likely in the southwest Pacific encompassing Niue, the Northern Cook Islands, Tonga, and Papua New Guinea. Near to below average rainfall is expected for all of those islands, except below average rainfall is forecast for Papua New Guinea. Near normal rainfall is forecast for the Austral Islands and Pitcairn Island. Enhanced convection is likely along the Equator extending from Western to Eastern Kiribati, and also near the Solomon Islands and Tuvalu. These regions are expected to receive near or above normal rainfall, with Western Kiribati forecast to receive above normal rainfall. No clear precipitation guidance is offered for Vanuatu, Fiji, Tuamotu Archipelago, Samoa, Tokelau, the Southern Cook Islands, New Caledonia, Wallis and Futuna, and the Society Islands.
The global models are continuing to show elevated temperatures in the near equatorial Pacific sea surface for the northwest corner of the Southwest Pacific. Some SST anomalies a have strengthened in the projections from past months. Above average sea surface temperatures are forecast for Eastern Kiribati. A region of near or above average sea surface temperatures is forecast around Papua New Guinea, the Solomon Islands, Western Kiribati, the Northern Cook Islands, the Marquesas and the Tuamotu archipelago. Near normal SSTs are forecast for the remainder of the southwest Pacific, except for Fiji, with near or below average SSTs.
The confidence in the multi-model ensemble forecast skill for this seasonal rainfall outlook is moderate to moderately high. In the past, the average region-wide hit rate for rainfall forecasts issued in October is 64%, 3% higher than the long-term average for all months combined. The SST forecast confidence is mostly high, but the greatest uncertainty is localised around the Marquesas and Eastern Kiribati.
Rainfall outlook map for October to December 2009
SST outlook map for October to December 2009