Rainfall outlook for February to April 2004
Above average rainfall in Western Kiribati and the Solomon Islands
Average or below average rainfall likely over Eastern Kiribati and the Marquesas Islands
Near average rainfall elsewhere
Enhanced convection is expected in the equatorial region west of the Date Line, resulting in above average rainfall in Western Kiribati and the Solomon Islands.
Suppressed convection is expected in the eastern equatorial Pacific which is likely to result in average or below average rainfall over Eastern Kiribati and the Marquesas Islands. Rainfall is expected to be near average elsewhere in the region with low or moderate skill. During this time of the year, rainfall is largely affected by any tropical cyclones and depressions affecting the region.Rainfall outlook map for February to April 2004
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 | 10:35:55 | (Above average) | Moderate |
| Solomon Islands | 15:35:50 | (Above average) | Moderate |
| Papua New Guniea | 30:40:30 | (Near average) | Low |
| New Caledonia | 30:45:25 | (Near average) | Low |
| Vanuatu | 30:40:30 | (Near average) | Low – Moderate |
| Tuvalu | 30:40:30 | (Near average) | Low – Moderate |
| Wallis and Futuna | 30:40:30 | (Near average) | Low – Moderate |
| Tokelau | 35:55:10 | (Near average) | Moderate |
| Samoa | 15:60:25 | (Near average) | Moderate |
| Fiji | 30:40:30 | (Near average) | Moderate |
| Tonga | 20:45:35 | (Near average) | Moderate |
| Niue | 20:45:35 | (Near average) | Moderate – High |
| Northern Cook Islands | 25:45:30 | (Near average) | Moderate – High |
| Southern Cook Islands | 15:55:30 | (Near average) | Moderate |
| Society Islands | 20:55:25 | (Near average) | Moderate |
| Austral Islands | 20:60:20 | (Near average) | Moderate |
| Tuamotu Island | 20:55:25 | (Near average) | Moderate |
| Pitcairn Island | 30:50:20 | (Near average) | Moderate |
| Eastern Kiribati | 40:40:20 | (Average or Below) | Moderate |
| Marquesas Islands | 40:40:20 | (Average or Below) | 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.