Tropical rainfall outlook: July to September 2006
An extensive region of enhanced convection is expected from Papua New Guinea southeast to Pitcairn Island, including the Solomon Islands, Vanuatu, Wallis and Futuna, Fiji, Tonga, Niue, the Southern Cook Islands, and the Society, Austral, and Tumotu Islands.
Suppressed convection is expected over Tuvalu and the Marquesas Islands, where rainfall is likely to be below average. Tokelau is expected to experience near or below average rainfall.
Rainfall over Western and Eastern Kiribati, New Caledonia, Samoa, and the Northern Cook Islands is expected to be near average.
The model skills are expected to be moderate during the dry season.
| Island group | Rainfall outlook | Outlook confidence |
|---|---|---|
| Papua New Guinea | 20:40:40 (Near or above average) | Moderate |
| Solomon Islands | 15:40:45 (Near or above average) | Moderate |
| Vanuatu | 20:40:40 (Near or above average) | Moderate |
| Wallis & Futuna | 20:40:40 (Near or above average) | Moderate |
| Fiji | 20:40:40 (Near or above average) | Moderate |
| Tonga | 20:40:40 (Near or above average) | Moderate |
| Niue | 20:40:40 (Near or above average) | Moderate |
| Southern Cook Islands | 20:40:40 (Near or above average) | Moderate |
| Society Islands | 20:40:40 (Near or above average) | Moderate |
| Austral Islands | 20:40:40 (Near or above average) | Moderate |
| Tuamotu Islands | 20:40:40 (Near or above average) | Moderate |
| Pitcairn Island | 20:40:40 (Near or above average) | Moderate |
| Western Kiribati | 30:40:30 (Near average) | Moderate |
| Eastern Kiribati | 20:45:35 (Near average) | Moderate |
| New Caledonia | 30:40:30 (Near average) | Moderate |
| Samoa | 25:50:25 (Near average) | Moderate |
| Northern Cook Islands | 25:50:25 (Near average) | Moderate |
| Tokelau | 40:40:20 (Near or below average) | Moderate |
| Tuvalu | 45:30:25 (Below average) | Moderate |
| Marquesas Islands | 50:30:20 (Below average) | 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: April to June 2006
Suppressed convection with below average rainfall was expected over Western Kiribati and Tuvalu, with near or below average rainfall in Eastern Kiribati and Tokelau. Regions of near or above average rainfall were expected from Papua New Guinea southeast to Pitcairn Island including Vanuatu, Wallis and Futuna, Tonga, Niue, the Southern Cook Islands, and the Austral Islands. Near average rainfall was expected elsewhere.
Areas of enhanced convection or above average rainfall affected the region near Papua New Guinea, and also Tonga and Niue. Suppressed convection or below average rainfall occurred over Western Kiribati, Tuvalu, and Samoa. Rainfall was higher than expected in Western Kiribati, otherwise the overall rainfall anomaly pattern was similar to what was expected. The 'hit' rate for the April-June 2006 outlook was about 70%.