The Southwest Pacific may experience either a reduced or typical number of tropical cyclones this upcoming season, as indicated by New Zealand’s National Institute of Water and Atmospheric Research (NIWA) and Metservice. The cyclone season is set to commence in November and will continue until April 30.
NIWA meteorologist Ben Noll forecasts a range of six to ten tropical cyclones for this season, with an average of nine. He emphasized that even with fewer cyclones than usual, severe impacts can still occur from less intense systems.
According to NIWA’s cyclone outlook report, the western Pacific region is expected to face a heightened risk of cyclones due to a developing La Niña, which causes warmer ocean waters to accumulate. This means that areas such as Papua New Guinea, Solomon Islands, Vanuatu, New Caledonia, and the Coral Sea region, extending towards Queensland, will need to maintain heightened cyclone awareness this season. Noll noted that these islands could potentially experience multiple tropical cyclones.
In contrast, eastern Fiji may see a normal to decreased likelihood of cyclones. Noll pointed out that these island groups typically experience several tropical cyclones each season, so even a forecast of normal or reduced activity can still result in significant impacts from any active weather systems.
Historical data from previous seasons with similar conditions suggests that several tropical cyclones may intensify to at least category 3 strength. The report mentioned that category 5 cyclones, characterized by sustained winds of 200 km/h or greater, have been common in many previous seasons with comparable conditions.
The forecast indicates that between three and four severe tropical cyclones reaching category 3 or higher could occur throughout the region, prompting communities to prepare adequately.
Last October, cyclone Lola was recorded as the strongest off-season tropical cyclone in the Southern Hemisphere, achieving category five strength, with winds reaching up to 215 km/h. Noll speculated that this event was likely related to the preceding El Niño.
He noted that historical precedents exist for early-season tropical cyclones during strong El Niño events, particularly in 1997, making Lola’s occurrence unusual but not entirely unprecedented. With the current La Niña, the cyclone season may take longer to commence, particularly in the eastern part of the basin where activity tends to increase later in the season. Consequently, the start of this season may not be as vigorous as last year.
While the Northern Hemisphere hurricane season has seen several impactful systems, including Helene and Milton, Noll remarked that the South Pacific’s conditions differ from those in the Atlantic, showing a long-term trend of slightly fewer cyclones.
Statistical data shows that the typical number of cyclones in the South Pacific has decreased from 10 to 9 over the past 30 years, aligning with climate change research indicating that while fewer cyclones may form, the intensity of those that do could be greater.
Last cyclone season, anticipated high numbers of cyclones due to the El Niño weather pattern resulted in only seven, which was two fewer than the historical average. Noll suggested that this recent trend of fewer cyclones could explain the unusual behaviors observed during El Niño periods.
Vanuatu and New Caledonia usually report the highest frequency of cyclones, averaging two to three in proximity each year. This season, both countries are expected to experience near-normal cyclone activity.