Three-month outlook

Tropical rainfall outlook: December 2007 to February 2008
Rainfall outlook map for December 2007 to February 2008.

Tropical rainfall outlook: December 2007 to February 2008

Rainfall outlook map for December 2007 to February 2008. (Click for enlargement)

Typical La Niña rainfall patterns are very likely to continue with a large area of suppressed convection along the equator from Kiribati, including Tuvalu, Tokelau, the Northern Cook Islands, and the Marquesas, Tuamotu,and Society Islands.

Near or below average rainfall is expected for Pitcairn Island.

Enhanced convection is likely to continue along a SPCZ displaced southwest, from the Solomon Islands through to the Austral Islands in French Polynesia. Included in the above average rainfall are Vanuatu, Wallis & Futuna, Tonga, Niue, and the Southern Cook Islands. Near or above average rainfall is expected in Papua New Guinea, New Caledonia, Fiji, and Samoa.

The confidence in the forecast model skill for this seasonal outlook is moderate to high for all Pacific Island countries. In the past, the average region-wide hit rate for forecasts issued in November has been 66%, 6% higher than the long term average for all months combined.

Island group Rainfall outlook Outlook confidence
Tonga 20:25:55 (Above) High
Niue 20:25:55 (Above) High
Vanuatu 20:30:50 (Above) High
Southern Cook Islands 20:30:50 (Above) High
Solomon Islands 25:30:45 (Above) High
Wallis & Futuna 20:35:45 (Above) High
Austral Islands 20:35:45 (Above) High
Papua New Guinea 20:40:40 (Near or above) Moderate - high
New Caledonia 20:40:40 (Near or above) Moderate-high
Fiji 20:40:40 (Near or above) Moderate - high
Samoa 20:40:40 (Near or above) Moderate - high
Pitcairn Islands 40:40:20 (Near or below) Moderate - high
Society Islands 40:35:25 (Below) Moderate
Tokelau 45:30:25 (Below) High
Northern Cook Islands 45:30:25 (Below) High
Tuamotu Islands 45:30:25 (Below) High
Tuvalu 50:30:20 (Below) High
Marquesas Islands 55:25:20 (Below) High
Western Kiribati 60:25:15 (Below) High
Eastern Kiribati 50:30:20 (Below) 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

Tropical cyclone Guba, the first this season, occurred just over and south of Papua New Guinea between 13–19November, with estimated maximum sustained wind speeds on 16 November of 139 km/h (category 1 on the Saffir-Simpson scale). Severe flooding was reported in parts of Papua New Guinea.

The La Niña conditions presently affecting the Pacific are still likely to influence tropical cyclones in several parts of the South Pacific this season, with a lower rate of occurrence expected in islands east of the Date Line, but with variablerisk elsewhere; all islands should remain vigilant.