Island Climate Update 56 - May 2005

Tropical Cyclones in the Cook Islands
Arona Ngari, Director, Cook Islands Meteorological Service
Background
Figure 1: Tropical cyclones from November 2004 through April 2005 (selected cyclones)
Figure 2: Tropical cyclones from November 2004 through April 2005
Figure 3: Cyclone damage.
During the 2004/05 tropical cyclone season, February was the most memorable among Cook Islanders living at home and abroad. It was the month that five cyclones (Meena, Nancy, Olaf, Percy, and Rae – See Figure 1) occurred within a period of five weeks.

Forecast validation
Forecast period: February to April 2005
Enhanced convection was expected over Eastern and Western Kiribati and Tokelau, with average or above average rainfall in Tuvalu, the Northern Cook Islands, the Austral Islands, and Pitcairn Island. Suppressed convection with below average rainfall was expected in the Marquesas Islands, and average or below average rainfall was expected over the Solomon Islands, Vanuatu, New Caledonia, and Fiji, as well as Samoa.

ENSO and Sea Surface Temperatures
The tropical Pacific Ocean warmed rapidly during the second half of April, resulting in the resurgence of borderline El Niño conditions (which could also be described as a "neutral but in a warm" state).

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 56 – May 2005
April's climate: High rainfall in parts of Vanuatu, Fiji, New Caledonia, Niue, and Tonga, caused by active South Pacific Convergence Zone: floods in Fiji. Active Inter-Tropical Convergence Zone near the equator. Warmer in Fiji, Samoa, and Tonga, as well as Northern and Central French Polynesia.

Climate developments in April 2005
The SPCZ (South Pacific Convergence Zone) was noticeably more active than in March, extending from the region north of Papua New Guinea southeast towards Fiji, and across to Niue. Enhanced convection was also associated with the ITCZ (Intertropical Convergence Zone), which extended from the Caroline Islands across the Date Line and further east about 5° north of the equator. Rainfall was at least 125% of average over much of Micronesia, Vanuatu, and parts of Fiji and New Caledonia, Niue, and Tonga, some locations recording more than 300% of normal.

Tropical rainfall outlook: May to July 2005
The tropical Pacific is in a neutral but borderline El Niño state. Because the forecast period is for the transitional months, the rainfall forecasts does not show a very strong pattern in the Pacific region.
However, enhanced convection is expected over the Solomon Islands, Vanuatu, and the Southern Cook Islands where rainfall is forecast to be near or above average.
Suppressed convection is likely over the Marquesas Islands, where rainfall is expected to be below average.

Tropical pacific rainfall - April 2005
Territory and station name
April 2005 rainfall total (mm)
Long-term average (mm)
April 2005 percent of average
Lowest on record (mm)
Highest on record (mm)
Records began
American Samoa
Pago Pago Airport
365.8
330
111
1966
Australia
Cairns Airport
185.2
190
97
15
1941
1941
Townsville Airport
19.2
62
31
0
546
1940
Brisbane Airport
848.0
90
94
3
502
1929
Sydney Airport
24.8
98
25
1929
Cook Islands
Penryhn
60.0
203
30
36
468
1937
Mauke
224.2
156
144
4
415
1929
Rarotonga Airport
205.8
211
9

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