The SPREP described the climate of Tuvalu as being: [I]nfluenced by a number of factors such as trade wind regimes, the paired Hadley cells and Walker circulation, seasonally varying convergence zones such as the South Pacific Convergence Zone (SPCZ), semi-permanent subtropical high-pressure belts, and zonal westerlies to the south, with the El Niño–Southern Oscillation (ENSO) as the dominant mode of year to year variability (…).

A number of studies suggest the influence of global warming could be a major factor in accentuating the current climate regimes and the changes from normal that come with ENSO events (…).

The 2011 report of the Pacific Climate Change Science Program published by the Australian Government,[10] describes a strong zonal (east‑to-west) sea-level slope along the equator, with sea level west of the International Date Line (180° longitude) being about a half metre higher than found in the eastern equatorial Pacific and South American coastal regions.

[12] The purpose of the meteorological programmes operated by the TMS is to gather data in the tropical western Pacific so as to work to achieve “accurate production of weather forecasts, seasonal and interannual climate forecasting (ENSO predictions), and understanding changes in climate and sea level for Tuvalu and its neighbouring Pacific Islands.

The radiosonde observations use a small, expendable instrument package is suspended below a 2 metres (6.6 ft) wide balloon filled with hydrogen or helium.

The data is shared with Regional Specialized Meteorological Centers (RSMCs) in Nadi, Wellington, Brisbane, Melbourne and Honolulu.

The weather modelling carried out by the RSMCs enables more accurate forecasts to be prepared for Tuvalu and for the tropical western Pacific.

New Zealand's National Institute of Water & Atmospheric Research (NIWA)[15] and collaborating agencies including the Meteorological Service of New Zealand and Pacific Island National Meteorological Services (including the TMS) issue the "Island Climate Update Tropical Cyclone Outlook" for the Pacific.

The Fiji Meteorological Service, while collaborating with NIWA and partners, also publishes its own seasonal forecast for the South Pacific basin between 160°E and 120°W.