During April – June 2011, a region of suppressed convection is likely in the southwest Pacific encompassing...
During April – June 2011, a region of suppressed convection is likely in the southwest Pacific encompassing Tuvalu, Tokelau, the Tuamotu Archipelago, the Society Islands and the Northern Cook Islands. Below average rainfall is expected for those island groups. Average or below average rainfall is expected for Wallis & Futuna, Samoa, the Marquesas and Eastern Kiribati. The Southwest Pacific Convergence Zone is expected to be displaced slightly to the southwest of normal for the forecast period. Papua New Guinea, Tonga, Niue and the Austral Islands are expected to receive above normal rainfall for the coming three months. Near or above average rainfall is forecast for New Caledonia, the Solomon Islands, Vanuatu, Fiji and the Southern Cook Islands. Near normal rainfall is expected for Western Kiribati and Pitcairn Island.
Many global models show weakening and contraction of the equatorial Pacific SST cold anomalies that exist close to the International Dateline in the coming months. In addition, the warm anomalies in and around the Coral Sea are expected to diminish. For April – June, above average SSTs are forecast for the Austral Islands. Average or above average sea surface temperatures are forecast for Papua New Guinea, Vanuatu, Tonga, Fiji, Pitcairn Island and the Southern Cook Islands. Near normal or below normal SSTs are forecast for Tuvalu, Wallis & Futuna, Western Kiribati, Eastern Kiribati, Samoa, the Society Islands, Tokelau, and the Tuamotu Archipelago. The Northern Cook Islands and the Marquesas are expected to experience below normal SSTs. Near normal SSTs are forecast for Niue, New Caledonia and the Solomon Islands.
The forecast confidence for the rainfall outlook is moderately high. The average region–wide hit rate for rainfall forecasts issued in April is 55%, 6% lower than all months combined. The SST forecast confidence is mostly high, with uncertainty localised near Eastern Kiribati and the Marquesas.
Rainfall anomaly outlook map for April to June 2011
SST anomaly outlook map for April to June 2011
NOTE: Rainfall and sea surface termperature estimates for Pacific Islands for the next three months are given in the tables above. The tercile probabilities (e.g., 20:30:50) are derived from the averages of several global climate models. They correspond to the odds of the observed rainfall or sea surface temperatures being in the lowest one third of the distribution, the middle one third, or the highest one third of the distribution. For the long term average, it is equally likely (33% chance) that conditions in any of the three terciles will occur. *If conditions are climatology, we expect an equal chance of the rainfall being in any tercile.