Tropical rainfall outlook: June to August 2006
A large region of enhanced convection with near or above average rainfall is expected from Papua New Guinea southeastwards to the Austral Islands, including the Solomon Islands, Vanuatu, Wallis and Futuna, Samoa, Tonga, Niue, the Southern Cook Islands, and Society Islands.
Near or below average rainfall is likely over the Tuamotu Islands.
Suppressed convection is expected over Tuvalu, Tokelau, the Northern Cook Islands, and the Marquesas Islands, where rainfall is expected to be below average.
Near average rainfall is likely for most of the other islands in the Southwest Pacific.
Rainfall forecast model skills tend to be low to moderate during this forecast period (June-August).
| Island group | Rainfall outlook | Outlook confidence |
|---|---|---|
| Papua New Guinea | 20:40:40 (Near or above average) | Moderate |
| Solomon Islands | 20:40:40 (Near or above average) | Moderate |
| Vanuatu | 20:40:40 (Near or above average) | Moderate |
| Wallis & Futuna | 20:40:40 (Near or above average) | Moderate |
| Samoa | 20:40:40 (Near or above average) | Low – 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 | 15:45:40 (Near or above average) | Moderate |
| Austral Islands | 20:40:40 (Near or above average) | Moderate |
| Fiji | 30:40:30 (Near average) | Moderate |
| New Caledonia | 30:35:35 (Near average) | Low – moderate |
| Western Kiribati | 30:45:25 (Near average) | Moderate |
| Eastern Kiribati | 30:40:30 (Near average) | Low – moderate |
| Pitcairn Island | 30:45:25 (Near average) | Low |
| Tuamotu Islands | 40:40:20 (Average or below) | Moderate |
| Tuvalu | 45:30:25 (Below) | Moderate |
| Tokelau | 45:25:30 (Below) | Moderate |
| Northern Cook Islands | 45:30:25 (Below) | Moderate |
| Marquesas Islands | 45:30:25 (Below) | 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: March to May 2006
Suppressed convection with below average rainfall was forecast for Eastern and Western Kiribati, with near or below average rainfall in Tuvalu, Tokelau, the Northern Cook Islands, and the Tuamotu and Marquesas Islands. Near or above average rainfall was forecast for Papua New Guinea, and from Fiji southeast to Pitcairn Island, including Tonga, the Southern Cook Islands, and the Austral Islands. Near average rainfall was expected elsewhere in the region.
Areas of enhanced convection or above average rainfall affected the region near Papua New Guinea, and also the Society Islands. Suppressed convection or below average rainfall occurred over Western Kiribati and Tuvalu. Rainfall was higher than expected in Northern French Polynesia and Tokelau, and lower than forecast in parts of Fiji. The overall rainfall anomaly pattern was similar to what was expected, the hit rate for the March-May 2006 outlook being about 60%.