Island Climate Update 108 - September 2009

The tropical Pacific is moving back towards La Niñaconditions. 

Aregion of suppressed convection was forecast for the southwest Pacific encompassing Tokelau, Tuvalu, the Northern Cook Islands, and the Marquesas, and below average rainfall was expected for those areas. Near normal rainfall was forecast for Pitcairn Island and the Tuamotu Archipelago. Enhanced convection was expected around Papua New Guinea, the Solomon Islands, Western Kiribati, Vanuatu, Niue, Tonga, the Southern Cook Islands, and the Austral Islands, and average or above average rainfall was anticipated for June through August.

Estimates of soil moisture shown in the map (bottom) are based on monthly rainfall for one station in each country.  Currently there are not many sites in the water balance model, but more stations will be included in the future.
The information displayed is based on a simple water balance technique to determine soil moisture levels. Addition of moisture to the available water already in the soil comes from rainfall, with losses via evapotranspiration. Monthly rainfall and evapotranspiration are used to determine the soil moisture level and its changes.

During September – November 2009, a region of suppressed convection is likely in the southwest Pacific encompassing Tokelau, the Northern Cook Islands, Tonga, Fiji, New Caledonia, and Papua New Guinea. Near to below average rainfall is expected for those areas. Below average rainfall is forecast for the Marquesas.Near normal rainfall is forecast for Niue, Southern Cook Islands, Wallis & Futuna, the Austral Islands and Pitcairn Island. Enhanced convection is likely along the Equator extending from Western to Eastern Kiribati, and also near the Solomon Islands.