Island Climate Update 67 - April 2006

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 67 – April 2006
March’s climate
Double Inter-Tropical Convergence Zone (ITCZ) evident in March; South Pacific Convergence Zone (SPCZ) much further south than average
Suppressed convection over Western and Eastern Kiribati, extending towards Samoa
Rainfall above average in the Southern Cook Islands and the Marquesas Islands; below average over much of Fiji, northern Tonga, and the Society

Tracking the South Pacific Convergence Zone: the SPCZ Position Index (SPI)
Dr J Salinger, NIWA
Figure 1. SPCZ Position Index (SPI; normalised Suva minus Apia pressure difference), November - April. Positive values indicate displacement toward Apia and negative values toward Suva.
Figure 2.

Climate developments in March 2006
Outgoing Long-wave Radiation anomalies for March 2006. (Click for enlargement and detail)
A "double ITCZ" structure, usually only seen during La Niña episodes, was evident in March. One region lay north of the equator from the Caroline Islands extending east across much of the Pacific. Another region extended east, south of the equator, from about the Date Line towards South America. The SPCZ was displaced much further south than average, extending from the Solomon Islands southeast toward New Caledonia, and south of Tonga.

Tropical rainfall outlook: March to May 2006.
Rainfall outlook map for April to June 2006. (Click for enlargement)
ENSO indicators in the equatorial Pacific are showing weakening La Niña conditions for the coming months. Global climate models are echoing this in the coming three month rainfall forecast patterns.
Suppressed convection is expected in the equatorial region around the Date Line where rainfall is expected to be below average for Western Kiribati and Tuvalu.

Tropical pacific rainfall - March 2006
Territory and station name
March 2006 rainfall
total (mm)
March 2006 percent
of average
Australia
Cairns Airport
588.6
131
Townsville Airport
161.6
78
Brisbane Airport
76.0
55
Sydney Airport
30.6
24
Cook Islands
Penrhyn
283.4
92
Aitutaki
97.6
50
Rarotonga Airport
246.4
145
Rarotonga EWS
216.4
127
Fiji
Rotuma
223.9
61
Udu Point
164.2
51
Nadi
189.6
56
Nausori
224.8
59
Ono-I-Lau
79.9
32
French Polynesia
Hiva Hoa, Atuona
326.2
168
Tahiti – Faa’a
59.4
33
Tuamotu, Takaroa
154.8
111
Gambi

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