Rainfall outlook for April to June 2003
Above average rainfall in Western and Eastern Kiribati, average or above average rainfall expected in the Solomon Islands, Tokelau and Samoa
Average or below average rainfall in New Caledonia and Fiji and below average rainfall in the Marquesas Islands
Continuing enhanced convection in the equatorial Pacific is expected to result in above average rainfall in Western and Eastern Kiribati. Average or above average rainfall is the most likely outcome for the Solomon Islands, Tokelau and Samoa.
Average or below average rainfall is expected in New Caledonia and Fiji. Suppressed convection is likely to result in below average rainfall for the Marquesas Islands. Rainfall is expected to be near average elsewhere.
The forecast model skills during this time of the year are generally reduced. Therefore the model skill is moderate to low for most islands in the region.
Rainfall outlook map for April to June 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) | Moderate–High |
| Eastern Kiribati | 10:25:65 | (Above) | Moderate |
| Solomon Islands | 20:40:40 | (Average or above average) | Moderate |
| Tokelau | 20:45:35 | (Average or above average) | Moderate |
| Samoa | 10:45:45 | (Average or above average) | Moderate |
| Papua New Guinea | 20:60:20 | (Near average) | Moderate |
| Vanuatu | 25:55:20 | (Near average) | Moderate |
| Tuvalu | 20:60:20 | (Near average) | Moderate |
| Wallis & Futuna | 20:60:20 | (Near average) | Moderate |
| Tonga | 20:60:20 | (Near average) | Moderate |
| Niue | 20:60:20 | (Near average) | Moderate |
| Northern Cook Islands | 30:55:15 | (Near average) | Moderate |
| Southern Cook Islands | 15:60:25 | (Near average) | Moderate |
| Society Islands | 10:60:30 | (Near average) | Low |
| Austral Islands | 25:50:25 | (Near average) | Moderate |
| Pitcairn Island | 35:45:20 | (Near average) | Moderate |
| Fiji | 35:40:25 | (Average or below average) | Moderate–Low |
| New Caledonia | 40:40:20 | (Average or below average) | Moderate–Low |
| Marquesas | 50:25:25 | (Below average) | High |
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.