7 May 2024

Fewer cyclones than predicted in El Nino summer - NIWA

11:10 am on 7 May 2024
Classroom at Melsisi in Vanuatu damaged by Cyclone Lola

Photo: Supplied / Joseph Molkis

The cyclone season in the South Pacific - which came to an end on 30 April - finished with fewer cyclones than what was forecast, during a bizarre El Niño event.

The El Niño weather pattern was supposed to result in a high number of cyclones in the South Pacific, however, there were only seven - two fewer than the long-term average.

Meteorologist Ben Noll, with New Zealand's National Institute of Water and Atmospheric Research (NIWA), said some of the outcomes of this El Niño were "unusual on a global scale and on a regional scale as well".

"Some of the things that were experienced in terms of weather and climate in the Pacific Islands may not have matched what those islands would have historically expected or experienced, in some of those big El Niño events in the past."

The cyclone season started with a string of severe tropical cyclones, including the earliest category five cyclone ever in October.

Cyclone Lola damage West Ambrym, on Ambrym island in Vanuatu

Photo: Supplied / Sam Tasso

Noll said September to December was most aligned with a typical El Niño event.

"There were definitely signs that things were going to be off to the races, and it was going to be quite a marathon in terms of cyclone season, but then we hit the new year."

Noll said there were unique characteristics in the ocean and atmosphere that prevented El Niño from producing more tropical cyclones.

However, NIWA forecast four severe cyclones which did eventuate. Droughts were also expected in some areas of the Pacific which was experienced, especially in parts of Micronesia.

"But there were then some countries that were anticipating perhaps a higher level of dryness or drought where that didn't end up necessarily eventuating," Noll said.

Kiribati was grappling with a drought after a triple dip La Niña, and experienced some flooding during this El Niño event.

"Too much rain too fast isn't a good thing, but countries did see some relief."

The Australian Bureau of Meteorology declared an end to the El Niño weather pattern as of April 16. NIWA has not yet declared it, but Noll said, "we're on the tail end".

The climate phenomonen El Niño Southern Oscillation (ENSO) system has two opposite states - El Niño and La Niña - both of which significantly alter weather patterns across the globe.

Noll said by the end of May we will be in ENSO-neutral, and could move into another La Niña later this year.

"It does seem like we're flipping from one end of the extreme to the other, and the behaviour of some of these ENSO events is also just a little bit out of the norm," he said.

"I'd say this is probably connected in some way to a changing climate and redistribution of heat across the Pacific, and that's then manifesting in basically different weather patterns."

Noll said out-of-season cyclones in the South Pacific did seem unlikely.

He said the ocean system was focusing its energy on the other side of the planet, closer to the Atlantic.

"They're actually anticipating a very, very active hurricane season in that part of the world, and because the warm water is really focused there, it does take the Pacific out of the spotlight for, I would say, cyclone risk."

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