Tropical rainfall outlook: October to December 2005
A large region of enhanced convection is expected from Papua New Guinea eastwards to the Solomon Islands, and Samoa.
Another region of near or above average rainfall is likely from Niue east to the Austral Islands, including the Cook Islands and the Society Islands.
Rainfall is expected to be near or below average over Western Kiribati and Tuvalu. Below average rainfall is forecast for Eastern Kiribati.
The rainfall forecast model skill is low to moderate for this time of the year.
| Island group | Rainfall outlook | Outlook confidence |
|---|---|---|
| Papua New Guinea | 15:45:40 (Near average or above) | Moderate |
| Solomon Islands | 15:40:45 (Near average or above) | Moderate |
| Samoa | 20:40:40 (Near average or above) | Moderate |
| Northern Cook Islands | 20:40:40 (Near average or above) | Moderate |
| Niue | 20:40:40 (Near average or above) | Moderate |
| Southern Cook Islands | 15:45:40 (Near average or above) | Moderate |
| Society Islands | 20:40:40 (Near average or above) | Moderate |
| Austral Islands | 15:45:40 (Near average or above) | Moderate |
| Vanuatu | 35:45:20 (Near average) | Moderate |
| Tokelau | 20:50:30 (Near average) | Moderate |
| New Caledonia | 35:40:25 (Near average) | Moderate |
| Wallis and Futuna | 25:50:25 (Near average) | Moderate |
| Fiji | 25:45:30 (Near average) | Low – moderate |
| Tonga | 30:50:20 (Near average) | Low – moderate |
| Pitcairn Island | 25:45:30 (Near average) | Low – moderate |
| Tuamotu Islands | 20:45:35 (Near average) | Moderate |
| Marquesas Islands | 30:50:20 (near average) | Moderate |
| Western Kiribati | 40:40:20 (Near average or below) | Moderate |
| Tuvalu | 40:40:20 (Near average or below) | Low – moderate |
| Eastern Kiribati | 45:35:20 (Below average) | Low – moderate |
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.
Forecast validation: July to September 2005
Enhanced convection with average or above average rainfall was expected in areas from the Solomon Islands to the Marquesas Islands, including Western Kiribati, Tuvalu, Tokelau, and the Northern Cook Islands. Suppressed convection with near or below average rainfall was expected over Fiji, the Tuamotu Islands, and Pitcairn Island. Near average rainfall was expected elsewhere in the region.
Areas of enhanced convection affected northern areas of Papua New Guinea, northern parts of the Solomon Islands, Niue, and Pitcairn Island (higher than expected). Rainfall was above average in central French Polynesia. Convection was suppressed in Western and Eastern Kiribati, and Tokelau, and rainfall was below average in the Northern Cook Islands. The overall 'hit' rate for the July-September 2005 rainfall outlook was about 65%.