December
Monthly climate
ENSO & SST
Forecast validation
Three-month outlook
Feature article
Tropical Pacific rainfall
Data sources
What is PI-GCOS?
Dr Mark Morrisey* and Howard Diamond#
The Pacific Islands-Global Climate Observing System (PI-GCOS) programme started in Apia, Samoa, in 2000 as a result of the first regional Global Climate Observing System (GCOS) workshop organised by the Secretariat of the Pacific Regional Environment Programme (SPREP) and the international GCOS Secretariat. It is a sub-programme of the GCOS aimed specifically at meeting the observing needs of Pacific Islands. Since the Apia workshop, a number of activities have been completed.
Forecast validation
Forecast period: September to November 2004
Enhanced convection was expected with above average rainfall over Eastern and Western Kiribati, with areas of average or above average rainfall in the Tuamotu Islands and Pitcairn Island. Suppressed convection with average or below average rainfall was expected in New Caledonia, Fiji, Tonga, and the Marquesas Islands.
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 51 – December 2004
November’s climate: The South Pacific Convergence Zone was active between Papua New Guinea, Nauru and Tuvalu, extended southeast to the Southern Cook Islands.
ENSO and sea surface temperatures (SST): Weak El Niño conditions are expected to continue in the tropical Pacific.
ENSO and Sea Surface Temperatures
The tropical Pacific Ocean continues in a weak El Niño state, but the atmosphere is still only partially coupled to the tropical ocean. The NINO3.4 average anomaly was +1.0°C in November (same as in October), and +1.0°C for September to November (up from +0.8 in August-October). Subsurface temperature anomalies were positive in the top 100 m across most of the Equatorial Pacific. Positive zonal wind anomalies were evident in November, but mostly west of the Date Line.
Climate developments in November 2004
The South Pacific Convergence Zone (SPCZ) was active in the region between Papua New Guinea, Nauru and Tuvalu, extending southeast to affect Rotuma Island (northern Fiji), Samoa, Niue, and the Southern Cook Islands. Enhanced rainfall between Papua New Guinea, Nauru and Tuvalu was caused by a continuation of cross-equatorial northwesterlies converging with stronger than normal southeast trade winds. The Inter-Tropical Convergence Zone (ITCZ) was active in the Pacific region (5-10° north of the Equator) about and east of the Date Line.
Tropical rainfall outlook: December 2004 to February 2005
The atmosphere is yet to fully couple with the tropical ocean. However, it is highly likely that the current weak El Niño event will still have some influence on rainfall patterns in the tropical Pacific region.
Rainfall is expected to be above average in the equatorial region of Western and Eastern Kiribati, extending south to include Tuvalu, Tokelau, and the Northern Cook Islands. Above average or near average rainfall is forecast for Pitcairn Island.
Tropical pacific rainfall - November 2004
Territory and station name
November 2004 rainfall total (mm)
Long-term average (mm)
November 2004 percent of average
Lowest on record (mm)
Highest on record (mm)
Records began
American Samoa
Pago Pago Airport
100.3
275
36
1966
Australia
Cairns Airport
99.4
97
102
302
372.0
1941
Townsville Airport
23.8
61
39
0.2
359.0
1940
Brisbane Airport
114.4
97
118
1.3
408.4
1929
Sydney Airport
54.0
83
65
1929
Cook Islands
Penrhyn
89.6
225
40
32
644
1937
Mauke
62.8
135
47
5
581
1929
Rarotonga Air
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