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New cyclone forecasting tool

Wednesday 22 July 2020 | Written by Jonathan Milne | Published in Weather

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New cyclone forecasting tool
The first long-range forecast, issued this week, predicts at most one cyclone in the Northern and Southern groups of the Cook Islands this summer – but that could change with the fruiting of the mangoes. TCOUTLOOK.COM 20072131

New science allows storm-planning six months out, aided by older knowledge like the arrival of mangoes, the incidence of fish poisoning, and the spread of predatory starfish.

Arona Ngari and Dr Andrew Lorrey have been working together for many years, divided by an ocean but united by their determination to find new ways to warn Pacific Islanders of dangerous cyclones.

Lorrey, a principal climate scientist at New Zealand’s National Institute of Water and Atmospheric Research, uses satellite imaging and tree ring analysis and computer modelling to predict changes in the climate.

Ngari, the director of Cook Islands Meteorological Service, does too – but he also watches to see how early the mango trees fruit, and how abundantly.

He talks with environmentalist Dr Teina Rongo about the proliferation of invasive crown-of-thorns starfish in the warming waters of the lagoons. And he tracks the number of people and animals reported poisoned by the reef-fish toxin ciguatera.

“Arona is almost always on the leading edge of adopting new guidance,” Lorrey said yesterday, “for example when we transitioned from statistical to dynamical models for seasonal climate outlooks.

“He really values what research can bring to the Cooks – on our past, present and future.

“I think there is a real willingness for Cook Islanders to take heed of advice and information and take action on it that is appropriate for the communities.”

That combination of old and new science contributes a leading edge to an important new model for the long-range forecasting of tropical cyclones in the Pacific – a tool developed by Lorrey and two other scientists at Australia’s University of Newcastle.

In a paper published in the respected Nature scientific journal yesterday, Dr Andrew Magee, Dr Andrew Lorrey and Dr Anthony Kiem reveal composite models providing outlooks for the different island groups of the Pacific, including Cook Islands.

“This provides meteorological services in the Cook Islands, French Polynesia and Kiribati with enhanced, location-specific outlooks.

In an accompanying article at TheConversation.com, they add: “Tropical cyclones produce extreme winds, large waves and storm surges, intense rainfall and flooding – and account for almost three in four natural disasters across the Southwest Pacific region,” they write.

“This improvement on existing extreme weather warning systems may save more lives and mitigate damage by providing information up to four months ahead of the cyclone season.”

And for now, they have some good news: according to their first monthly outlook using the combined models, Cook Islands can hope for a quiet cyclone season.

It will be a La Niña climate pattern this summer with no more than one tropical cyclone in the northern group, and the same in the southern group.

That could change, of course. The outlooks will be delivered to Cook Islands Meteorological Service and other Pacific forecasters every month.

And if Ngari sees the mango trees fruiting abundantly from early September, that data will be fed back into the computer models – and could provide Cook Islanders early warning as they prepare to reopen their tourist resorts.

“It it’s a boomer of a crop year, then it’s a sign of an El Niño and a high risk of cyclones,” he says.

So here’s one more question: how does it actually help us to know six months out whether there’s a bad cyclone season on its way?

Ngari explains: “It gives us confidence that people are aware of the risk, so people might take more time to look after their properties and clean their water storage in the North.

“In the South, they can prepare their tourist accommodation and gently encourage tourists to come for shorter 7 to 10-day stays over summer.”

To prove the point of the importance of early warnings, Emergency Management Cook Islands director Charles Carlson yesterday welcomed the first long-range outlook.

He said the indication of fewer cyclone this summer was good news for the country – which is already battered by economic storms.

“It is always good to have accurate forecasting for the weather and notice they are now using more models for forecasting,” he said.

“Over the years, Cook Islands Meteorological Service and Emergency Management Cook Islands have revived our traditional knowledge for forecasting cyclones.

“It is important that we combine science with our traditional knowledge after all these are knowledge that has been proven by our forefathers for generations.”