Three-month outlook
Rainfall outlook for March to May 2003
Above average rainfall in Western and Eastern Kiribati, average or above average rainfall expected in Tuvalu
Average or below average rainfall from New Caledonia east to Niue and parts of French Polynesia
Below average rainfall in the Marquesas Islands
Enhanced convection is expected to continue over Western and Eastern Kiribati resulting in above average rainfall. Tuvalu is expected to experience average or above average rainfall.
Below average or average rainfall is the most likely outcome from New Caledonia, to Niue, including Fiji, Tonga, Samoa, and the Austral Islands.
Below average rainfall is expected in the Marquesas. Near average rainfall is expected elsewhere.
The forecast model skills for this outlook are generally moderate for nearly all islands in the region.
Rainfall outlook map for March to May 2003
Probabilities of rainfall departures from average
Broad-scale rainfall patterns and anomalies in the southern tropical Pacific area are estimated from the state of large-scale regional climate factors, such as La Niña or El Niño, their effect on the South Pacific and Tropical Convergence Zones, surface and sub-surface sea temperatures, and computer models of the global climate.
Rainfall estimates for the next three months for Pacific Islands are given in the adjacent 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.
The probabilities shown express the expected shift in the distribution from the long-term average, based on predictions of oceanic and atmospheric conditions. The amount of inter-model forecast consistency is indicated by the levels of confidence expressed in the table.
| Island Group | Rainfall Outlook | Confidence in the Outlook | |
|---|---|---|---|
| Western Kiribati | 10:20:70 | (Above) | High |
| Eastern Kiribati | 10:20:70 | (Above) | High |
| Tuvalu | 20:40:40 | (Average or above average) | Moderate |
| Papua New Guinea | 20:45:35 | (Near average) | Moderate |
| Solomon Islands | 30:50:20 | (Near average) | Moderate |
| Vanuatu | 30:50:20 | (Near average) | Moderate |
| Wallis & Futuna | 30:60:10 | (Near average) | Moderate |
| Tokelau | 15:50:35 | (Near average) | Moderate |
| Northern Cook Islands | 10:60:30 | (Near average) | Moderate |
| Southern Cook Islands | 15:70:15 | (Near average) | Moderate |
| Society Islands | 35:50:15 | (Near average) | Low |
| Pitcairn Island | 25:50:25 | (Near average) | Moderate |
| New Caledonia | 40:40:20 | (Average or below average) | Moderate |
| Fiji | 40:40:20 | (Average or below average) | Moderate |
| Tonga | 40:40:20 | (Average or below average) | Moderate |
| Niue | 40:40:20 | (Average or below average) | Moderate |
| Samoa | 40:50:10 | (Average or below average) | Moderate |
| Austral Islands | 45:40:15 | (Average or below averge) | Low |
| Marquesas | 60:30:10 | (Below average) | Moderate |
Rainfall outcomes as estimated from models and historical records. The third column indicates the probability of bottom (below), middle (average) or top (above) tercile rainfall, where a percentage is given. The rainfall outlook (second column) is subjectively estimated from the probabilities of bottom, middle and top terciles.