During September – November 2009, a region of suppressed convection is likely in the southwest Pacific encompassing Tokelau, the Northern Cook Islands, Tonga, Fiji, New Caledonia, and Papua New Guinea. Near to below average rainfall is expected for those areas. Below average rainfall is forecast for the Marquesas.Near normal rainfall is forecast for Niue, Southern Cook Islands, Wallis & Futuna, 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. These regions are expected to receive near or above normal rainfall, with Western Kiribati and the Solomon Islands forecast to receive above normal rainfall. No clear precipitation guidance is offered for Vanuatu, Tuamotu Archipelago, Samoa, 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.
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 September is 67%, 6% 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 September to November 2009
Sea surface temperature outlook map for September to November 2009