Island Climate Update 24 - September 2002

ENSO Update
Current El Niño Situation
Fig 1 Southern Oscillation Index (up to August 2002)
Fig 2 Sea Surface Temperature Anomalies for August 2002.
Fig 3 Sub-surface temperature along the equator for August 2002.
Fig 4 TAO/TRITON 5-Day Equatorial SST and winds.
An El Niño event is under way in the tropical Pacific and there is a strong consensus that it will continue into the Southern Hemisphere wet season, although it is likely to be much weaker than the 1997/98 event.

Forecast validation
Forecast period: June to August 2002
Rainfall was projected to trend towards above average in Western and Eastern Kiribati and trend towards below average in Papua New Guinea, from New Caledonia northeast to Samoa, and in the Marquesas and Austral Islands of French Polynesia. Average rainfall was forecast for other areas.
The rainfall outlook was correct for countries near the equator, where rainfall is well correlated to the SOI. However, rainfall was higher than expected in the Southern Cook Islands and Pitcairn.

ENSO and Sea Surface Temperatures
The Central Equatorial Pacific remains warmer than average
El Niño likely to persist into early 2003
During August, there has been some intensification in patterns of sea surface temperatures (SST) in the equatorial central Pacific, where some areas particularly around Kiribati are more than 1.5°C above average .
There has been cooling in the Coral Sea especially around the northern cost of Australia, while SSTs have warmed along the southern coast of Australia.

An extensive region of enhanced convection in the western-central tropical Pacific
Enhanced convection affected a wide area of the western-central tropical Pacific in August. This covered much of the region between 20°N and 15°S and 160°E and 170°W, enhancing rainfall from Micronesia across to Hawaii, Nauru, Kiribati and Tuvalu. Extremely high August rainfall (300-500% of average) was recorded throughout much of Western Kiribati.

Rainfall outlook for August to October 2002
Above average or average rainfall in equatorial latitudes from west to east and Pitcairn Island
Below average or near average rainfall from Papua New Guinea to New Caledonia across to the Southern Cook Islands
Mainly average rainfall in other areas
The SPCZ extended east from the south of Tuvalu to the east of Samoa in August, but it continued to be weak with little activity further east in the Southwest Pacific.
Rainfall is projected to be above average in Western and Eastern Kiribati, while Tuvalu, Tokelau, Wallis & Futuna and Pitcairn Islan

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.
Number 24 – 6 September 2002
August’s Climate: A very extensive area of enhanced convection (larger than the continent of Australia) affected a wide area of the western-central tropical Pacific in August, enhancing rainfall from Micronesia across to Hawaii, Nauru, Kiribati and Tuvalu. Record high August rainfall occurred throughout much of Western Kiribati.

Sources of South Pacific rainfall data
This bulletin is a multi-national project with important collaboration from the following Pacific nations:
American Samoa
Australia
Cook Islands
Fiji
French Polynesia
Kiribati
New Caledonia
New Zealand
Niue
Papua New Guinea
Pitcairn Island
Samoa
Solomon Islands
Tokelau
Tonga
Tuvalu
Vanuatu
Requests for Pacific island climate data should be directed to the Meteorological Services concerned.
Acknowledgements
This bulletin is made possible with financial support from the New Zealand Agency for International Development (NZAID), Wellington, New Zealand, wi