Rainfall outlook for January to March 2004
Average or above average rainfall likely from the Solomon Islands east southeast to the Austral Islands
Below average rainfall likely in the Marquesas Islands
Near average rainfall elsewhere in the region
Enhanced convection is expected in parts of the tropical Southwest Pacific resulting in average or above average rainfall from the Solomon Islands trending east to the Austral Islands, including Samoa, the Northern Cook Islands and the Society and Austral Islands.
However, below average rainfall is expected for the Marquesas Islands. The rest of the region is expected to experience near average rainfall over the next three months.
Moderate to high model skill usually prevails during the wet season.
Rainfall outlook map for January to March 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 | |
|---|---|---|---|
| Solomon Islands | 20:45:35 | (Average or Above) | Moderate |
| Samoa | 10:50:40 | (Average or Above) | Moderate |
| Northern Cook Islands | 10:45:45 | (Average or Above) | Moderate |
| Society Islands | 20:40:40 | (Average or Above) | Moderate |
| Austral Islands | 15:45:40 | (Average or Above) | Moderate |
| Western Kiribati | 20:50:30 | (Near average) | Moderate |
| Eastern Kiribati | 30:35:35 | (Near average) | Moderate |
| Papua New Guniea | 30:50:20 | (Near average) | Moderate |
| Vanuatu | 15:55:30 | (Near average) | Moderate–High |
| New Caledonia | 25:50:25 | (Near average) | Moderate |
| Tuvalu | 20:45:35 | (Near average) | Moderate |
| Wallis and Futuna | 15:50:35 | (Near average) | Moderate |
| Tokelau | 20:50:30 | (Near average) | Moderate |
| Fiji | 30:50:20 | (Near average) | Moderate–High |
| Tonga | 20:60:20 | (Near average) | Moderate |
| Niue | 20:50:30 | (Near average) | Moderate |
| Southern Cook Islands | 20:55:25 | (Near average) | Moderate–High |
| Tuamotu Island | 20:50:30 | (Near average) | Moderate |
| Pitcairn Island | 25:50:25 | (Near average) | Moderate |
| Marquesas Islands | 50:30:20 | (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.
Tropical Cyclone Update
‘Heta’, the first severe tropical cyclone (category 5 – most severe) of the season, originated from a disturbance north of Fiji on 28 December. It moved to develop into a tropical cyclone just west of Atafu, the northernmost part of the Tokelau Islands on 2 January.
Heta continued to track south, passing west of Samoa on 5 January, and then southeast, with sustained winds near its centre exceeding 220 km/h. The western Samoan island of Savai’i experienced 145–160 km/h wind gusts, and on the main island of Upolu, Apia airport was closed. A few roofs were lifted. Crops were destroyed, roads were blocked, bridges were damaged, and power cut. Heavy rainfall accompanied the high winds. American Samoa reported losses equivalent to $226 million, due to roads washed away.
Heta also caused extensive damage to utlities, homes and vegetation in American Samoa. The acting Governor of American Samoa declared a “state of emergency” for the territory.
The cyclone increased in intensity and estimated maximum sustained wind speeds reached 260 km/h with gusts to 300 km/h as it approached Niue, its centre passing just west (within 50 km) of Niue on the evening of 6 January. The lowest mean sea level pressure recorded on Niue was 977.2 hPa. Niue Island was devastated, with estimated wind speeds of 220 km/h and gusts of 275 km/h.
One person died and her baby girl was severely injured when their Alofi house collapsed. Several other people were also injured. Many people were left homeless. Much property was severely damaged or destroyed (including the hospital), many roads were closed, telecommunications and electricity were cut, and crops were badly damaged from the high winds and intense rainfall. A national disaster was declared.
The Cook Islands was another small nation that felt some of Heta’s fury, experiencing 6-m swells. The worst affected area was the west coast of the main island Rarotonga, a popular tourist destination. The system gradually began to decay when it tracked further southeast over sub-tropical waters.