Tropical rainfall outlook: March to May 2008
La Niña conditions are still very likely to influence rainfall patterns during this period, with a large area of suppressed convection very likely along the equatorial Pacific from Western Kiribati to Eastern Kiribati, including the Solomon Islands, Tuvalu, the Society Islands, Tuamotu, and the Marquesas Islands. Near or below average rainfall is likely for the Northern Cook Islands and Wallis & Futuna, while average rainfall is likely for Samoa, Tonga, and Pitcairn Island.
Enhanced convection with above average rainfall is likely in New Caledonia, the Southern Cook Islands, and the Austral Islands, while Papua New Guinea, Vanuatu, Fiji, and Niue are expected to receive near or above average rainfall.
The confidence in the forecast model skill for this seasonal outlook is moderate to moderately high for most Pacific Island countries. In the past, the average region-wide hit rate for forecasts issued in March is 63%, 3% higher than the long term average for all months combined.
| Island group | Rainfall outlook | Outlook confidence |
|---|---|---|
| New Caledonia | 20:35:45 (Above) | Moderate - high |
| Austral Islands | 20:35:45 (Above) | Moderate - high |
| Cook Islands (Southern) | 25:30:45 (Above) | Moderate |
| Niue | 25:35:40 (Near or Above) | Moderate - high |
| Vanuatu | 25:35:40 (Near or Above) | Moderate - high |
| Fiji | 25:35:40 (Near or Above) | Moderate |
| Pitcairn Islands | 30:35:35 (Near normal) | Moderate - high |
| Tonga | 30:35:35 (Near normal) | Moderate - high |
| Papua New Guinea | 35:35:30 (Near normal) | Moderate - high |
| Samoa | 35:35:30 (Near normal) | Moderate |
| Society Islands | 40:35:25 (Near or Below) | Moderate |
| Wallis & Futuna | 40:35:25 (Near or Below) | Moderate - high |
| Solomon Islands | 40:30:25 (Below) | Moderate |
| Marquesas Islands | 50:30:20 (Below) | Moderate- high |
| Tokelau | 50:30:20 (Below) | Moderate |
| Tuamotu Islands | 50:30:20 (Below) | Moderate- high |
| Cook Islands (Northern) | 55:25:20 (Below) | Moderate |
| Tuvalu | 55:25:20 (Below) | Moderate - high |
| Kiribati (Eastern) | 60:25:15 (Below) | Moderate- high |
| Kiribati (Western) | 60:25:15 (Below) | Moderate - high |
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.
Tropical cyclones
One tropical cyclone (TC) affected the South Pacific region in February. TC Gene formed on the 27 January northeast of Fiji and tracked southwest toward New Caledonia, reaching Category 3 strength. Maximum sustained winds of 100 knots were reached late on 31 January. TC Gene subsequently swung to the southeast and deteriorated along a southeast exit path into the extra-tropics on 1 February. There was only one other major depression that developed in the South Pacific during the month, but it did not develop into a cyclone. March is normally an active month for tropical cyclones, and the development of mature La Niña conditions at present will continue to influence tropical cyclones in several parts of the South Pacific region.