Tropical rainfall and SST outlook: December 2012 to February 2013

The tropical Pacific is still warmer than usual, but the atmospheric circulation is close to normal for this time of the year. 

The dynamical models indicate both the ITCZ and the SPCZ will be positioned south of normal for December 2012 – February 2013.

Slightly drier – than – normal conditions are likely to affect areas south of the Equator to the east of the Dateline, as well as parts of the Coral Sea and the north Tasman Sea.

Near or above normal rainfall is forecast for the Northern Cook Islands, Western Kiribati, Niue, Fiji, Samoa, the Society Islands, the Solomon Islands and Tokelau.

Near normal rainfall is expected for the Austral Islands, the Southern Cook Islands, Papua New Guinea, Pitcairn Island, the Tuamotu archipelago, Tuvalu, Vanuatu, Wallis & Futuna and the Federated States of Micronesia.

Normal or below normal rainfall is forecast for Eastern Kiribati, Tonga, the Marquesas and New Caledonia.

The global model ensemble shows some patterns that are similar to a weak El Niño in the SST field, however those anomalies are weaker than in previous forecasts.

Cooler than normal SST are forecast for the subtropical latitudes of the southwest Pacific.

Near normal or above normal SSTs are forecast for Eastern Kiribati, Western Kiribati, the Northern Cook Islands, Tuvalu, Tokelau, Niue and Tonga. Normal sea surface temperatures are expected elsewhere.

The confidence for the rainfall outlook is moderate to high. The average region–wide hit rate for rainfall forecasts issued in December is 67%, four points higher than the long–term average for all months combined. The SST forecast confidence is moderate to high across the region, and uncertainty is greatest for Eastern Kiribati and the Marquesas. 

Rainfall anomaly outlook map for December 2012 to February 2013
SST anomaly outlook map for December 2012 to February 2013
NOTE: Rainfall and sea surface termperature estimates for Pacific Islands for the next three months are given in the tables below. 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.