Island Climate Update 111 - December 2009

An overview of the present climate in the tropical South Pacific Islands, with an outlook for the coming months, to assist in dissemination of climate information in the Pacific region.

In this issue

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    Climate developments in November 2009

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    Data Sources

    This bulletin is a multi-national project with important collaboration from the following Pacific nations:
    American Samoa
    Cook Islands
    French Polynesia
    New Caledonia
    New Zealand
    Papua New Guinea
    Pitcairn Island
    Solomon Islands
    Requests for Pacific island climate data should be directed to the Meteorological Services concerned.
    Your comments and ideas about the Island Climate Update are welcome. Please contact:
    Dr Andrew Lorrey, NIWA,
    41 Market Place, Auckland, New Zealand
    E-mail: [email protected]
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    Number 111 - December 2009
    November’s climate
    • The South Pacific Convergence Zone (SPCZ) was displaced southwest of normal near Papua New Guinea and the Solomon Islands.
    • Suppressed convection in the central part of the Southwest Pacific near Fiji and Samoa.
    • Mostly well below normal rainfall for many parts of Vanuatu, New Caledonia, Fiji, and Tonga.
    El Niño/Southern Oscillation (ENSO), seasonal rainfall, and sea surface  temperature forecasts
    • El Niño conditions exist in the equatorial Pacific.
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    El Niño/Southern Oscillation (ENSO)

    During November, El Niño conditions in the equatorial Pacific strengthened during October and November. Equatorial sea surface temperature anomalies increased across much of the Pacific. For the last two months, NINO4 has been more positive than NINO3. In November, NINO3 and NINO4 anomalies were +1.5°C and +1.7°C (3–month SON means +1.3°C and +1.4°C).
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    Soil moisture in November 2009

    Estimates of soil moisture shown in the map (right) 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.
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    Tropical Pacific rainfall – November 2009

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    Tropical Cyclone guidance: November 2009 to April 2010

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    Tropical rainfall and SST outlook: December 2009 to February 2010

    During December 2009 – February 2010, a region of suppressed convection is likely in the southwest Pacific encompassing Niue, Tonga, New Caledonia, and Vanuatu. Below average rainfall is expected for all of those island groups. Near or below normal rainfall is expected for Fiji, Wallis & Futuna, the Southern Cook Islands, the Marquesas, and Pitcairn Island. Enhanced convection is likely along the Equator extending from Western to Eastern Kiribati, and also near Tokelau, with an expectation of above rainfall for those islands.
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    Forecast validation: September to November 2009

    A region of suppressed convection was forecast for the southwest Pacific encompassing Tokelau, the Northern Cook Islands, Tonga, Fiji, New Caledonia, and Papua New Guinea. Near to below average rainfall was expected for those areas. Below average rainfall was forecast for the Marquesas. Near normal rainfall was forecast for Niue, Southern Cook Islands, Wallis & Futuna, the Austral Islands and Pitcairn Island.