Rainfall outlook for May to July 2003
Average or above average rainfall is expected in many equatorial regions
Average or below average rainfall in Fiji, Tonga, Niue, and the Tuamotu Islands
Below average rainfall in the Marquesas Islands
The enhanced equatorial convection that was prevalent over last year has now dissipated with the strengthening of the easterly tradewinds across the equatorial Pacific. Average or above average rainfall is the most likely outcome for Western and Eastern Kiribati, the Solomon Islands, Tuvalu, Tokelau and the Society Islands. Average or below average rainfall is expected in Fiji, Tonga, Niue and the Tuamotu Islands. Below average rainfall is more likely for the Marquesas Islands.
Near average rainfall is expected elsewhere in the region.
The forecast model skills are reduced at this time of the year due to the transition from the wet to the dry season.
Rainfall outlook map for May to July 2003
Impacts of Tropical Cyclone ERICA on New Caledonia
Tropical Cyclone ‘ERICA’ affected New Caledonia when it passed along the west coast of the main island on the 14th of March. Erica was the strongest tropical cyclone on record to affect New Caledonia since ‘BETI’ which devastated the country in 1996.
Erica brought destructive hurricane force winds. A new maximum wind gust record of 234 km/h was measured at Koniambo (895 m elevation) and Vavouto. The old maximum was 230 km/h at Montagne des Sources (780 m elevation) for Beti. In Nouméa the previous maximum of 159 km/h recorded for tropical cyclone Colleen in 1969, was shattered with wind gusts up to 202 km/h. A sustained maximum wind gust of 166 km/h was recorded at Vavouto, exceeding the former record of 144 km/h at Poindimié during tropical cyclone Beti in 1996.
The estimated costs of rehabilitation for New Caledonia are US$7 million for the telephone network, US$7.5 million for the electricity network and US$3.5 million for the crops. These costs do not include the damage to the infrastructure. Meteo-France had to fund US$200,000 for repairs to its building.
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 average) | Moderate – Low |
| Eastern Kiribati | 20:40:40 | (Average or above average) | Moderate – Low |
| Solomon Islands | 15:45:40 | (Average or above average) | Moderate |
| Tokelau | 15:45:40 | (Average or above average) | Moderate |
| Tuvalu | 15:45:40 | (Average or above average) | Moderate |
| Society Islands | 15:45:40 | (Average or above average) | Moderate |
| Papua New Guinea | 30:50:20 | (Near average) | Moderate |
| Vanuatu | 35:50:15 | (Near average) | Moderate |
| Samoa | 20:45:35 | (Near average) | Moderate |
| Wallis & Futuna | 20:45:35 | (Near average) | Moderate |
| New Caledonia | 35:45:20 | (Near average) | Moderate – Low |
| Northern Cook Islands | 20:50:30 | (Near average) | Moderate |
| Southern Cook Islands | 30:50:20 | (Near average) | Moderate |
| Austral Islands | 25:50:25 | (Near average) | Low |
| Pitcairn Island | 20:60:20 | (Near average) | Moderate |
| Fiji | 35:40:25 | (Average or below average) | Moderate |
| Tonga | 35:40:25 | (Average or below average) | Moderate – Low |
| Niue | 35:40:25 | (Average or below average) | Moderate – Low |
| Tuamotu Islands | 35:45:20 | (Average or below average) | Low |
| Marquesas Islands | 50:35:15 | (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.