June
Monthly climate
ENSO & SST
Forecast validation
Three-month outlook
Feature article
Tropical Pacific rainfall
Data sources
2004-05 Tropical Cyclone Season Summary
Stuart Burgess, NIWA
Figure 1. The number of Southwest Pacific tropical cyclones for the 2004/05 season (solid red bar) compared with frequencies during the past 30 years. The horizontal green line indicates the 30-year average.* Not including Ingrid which originated west of 150° E.
Figure 2.
Forecast validation
Forecast period: March to May 2005
Enhanced convection and above average rainfall were expected over Western Kiribati, with average or above average rainfall over Eastern Kiribati, Tuvalu, Tokelau, the Austral Islands, and Pitcairn Island. Suppressed convection with below average rainfall was expected over the Marquesas Islands and rainfall was expected to be average or below average over Fiji.
ENSO and Sea Surface Temperatures
The tropical Pacific Ocean remains in a neutral but warm state (which may also be described as a weak El Niño state), much as it was in April. The rapid changes occurring in late April/early May, towards a possible El Niño state, appear to have been a short-lived perturbation. The Southern Oscillation Index (SOI) dropped slightly last month to -1.5, making the March-May mean -1.0.
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 57 – June 2005
May's climate: South Pacific Convergence Zone further north and east than usual, Intertropical Convergence Zone near the equator. High rainfall in parts of New Caledonia and central French Polynesia, low rainfall in Fiji and northern Tonga.
Climate developments in May 2005
The South Pacific Convergence Zone (SPCZ) was further north and east than usual in May, extending from the region north of Tuvalu over the Northern Cook Islands and southeast through central French Polynesia. Enhanced convection occurred over much of the Solomon Islands, Vanuatu, and New Caledonia, and also central French Polynesia. May rainfall was about 300% of normal in parts of New Caledonia and central French Polynesia, and at least 125% of normal over much of Tuvalu.
Tropical rainfall outlook: June to August 2005
The Pacific region will continue to see the lingering effects of the warm event which dissipated earlier this year, especially on the rainfall patterns.
Based on the model guidance, enhanced convection is expected over Eastern Kiribati, where rainfall is forecast to be above average. Western Kiribati and Tuvalu are expected to experience near or above average rainfall.
Near or below average rainfall is expected over Fiji and the Marquesas Islands of French Polynesia.
Tropical pacific rainfall - May 2005
Territory and station name
May 2005 rainfall total (mm)
Long-term average (mm)
May 2005 percent of average
Lowest on record (mm)
Highest on record (mm)
Records began
American Samoa
Pago Pago Airport
293.4
245
120
1966
Australia
Cairns Airport
19.6
96
20
6
322
1941
Townsville Airport
21.0
36
58
0
206
1940
Brisbane Airport
52.8
99
53
3
617
1929
Sydney Airport
50.4
97
52
4
585
1929
Cook Islands
Penryhn
93.6
183
51
24
437
1937
Mauke
25.6
154
17
3
499
1929
Rarotonga Airport
36.3
169
21
21
693
192
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