Rainfall outlook for March to May 2004
Enhanced convection in Western Kiribati, Vanuatu, the Wallis and Futuna, and the Society Islands
Average or below average rainfall likely over the Tuamotu Islands and Pitcairn Island
Below average rainfall is expected in the Marquesas Islands
Enhanced convection is expected in Western Kiribati, Vanuatu, Wallis and Futuna and the Society Islands, resulting in average or above rainfall around this region. Average or below average rainfall is expected in the Tuamotu Islands and Pitcairn Island region while suppressed convection is expected over the Marquesas Islands, where rainfall is likely to be below average. Near average rainfall is likely elsewhere in the region. The model skills are low to moderate due to lack of predictability during this time of the year.
Rainfall outlook map for March to May 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 | 20:40:40 | (Average or above) | Low |
| Vanuatu | 15:45:40 | (Average or above) | Moderate |
| Wallis and Futuna | 20:40:40 | (Average or above) | Moderate |
| Society Islands | 15:45:40 | (Average or above) | Moderate |
| Eastern Kiribati | 25:45:30 | (Near average) | Low |
| Papua New Guinea | 20:45:35 | (Near average) | Moderate |
| Solomon Islands | 20:45:35 | (Near average) | Moderate |
| Tuvalu | 20:50:30 | (Near average) | Moderate |
| Fiji | 35:40:25 | (Near average) | Moderate |
| Tokelau | 30:50:20 | (Near average) | Moderate |
| Samoa | 20:50:30 | (Near average) | Moderate |
| New Caledonia | 25:45:30 | (Near average) | Low |
| Tonga | 20:50:30 | (Near average) | Moderate |
| Niue | 20:50:30 | (Near average) | Moderate |
| Northern Cook Islands | 30:50:20 | (Near average) | Moderate |
| Southern Cook Islands | 25:50:25 | (Near average) | Moderate |
| Austral Islands | 20:50:30 | (Near average) | Moderate |
| Tuamotu Island | 40:45:15 | (Average or below) | Moderate |
| Pitcairn Island | 40:45:15 | (Average or below) | Moderate |
| Marquesas | 50:30:20 | (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.