ST Explains: Unravelling typhoons and emerging climate trends
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High waves hit Cua Lo beach as Typhoon Kajiki approaches Nghe An province in Vietnam on Aug 25.
PHOTO: REUTERS
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SINGAPORE – The Pacific region is currently in the grip of typhoon season, with Vietnam, Laos and Thailand reeling from Typhoon Kajiki.
Typhoons are spinning tropical storms with strong winds and heavy rain – also called hurricanes or cyclones in other regions.
The Straits Times speaks to climate scientists to break down how these powerful tropical storms take shape.
Could a typhoon ever hit Singapore?
Singapore is generally shielded from typhoons because it is located close to the Equator. Tropical cyclones need a spinning force from the Earth’s rotation, called the Coriolis force, which is too weak near the Equator, said Dr Dhrubajyoti Samanta, senior research fellow at the NTU Earth Observatory of Singapore (EOS).
But Typhoon Vamei in December 2001 was a rare exception, formed just 160km north of the Equator. It swept by the north of Singapore on Dec 27, dumping 10 per cent of the entire year’s rain in one day and causing flight delays.
“Typhoon Vamei in 2001 served as a wake-up call for Singapore and other equatorial regions by demonstrating that a historically low risk of tropical cyclones does not equate to zero risk,” said Professor Adam Switzer from EOS and the NTU Asian School of the Environment.
Does climate change cause typhoons?
No. Typhoons, hurricanes and cyclones are a natural weather phenomenon.
But climate change makes them more severe, causing greater damage to infrastructure and economies. This is because warmer oceans provide extra fuel – heat and moisture – for these tropical storms to intensify.
Over the past few decades, the number of tropical cyclones has also decreased. A study in 2022 found that the yearly number of tropical cyclones globally has decreased by around 13 per cent during the 20th century.
Was climate change behind the 2024 supercharged typhoon season in the Philippines?
The unusual run of six back-to-back typhoons within 30 days in October and November 2024 was not directly linked to climate change, but scientists have mixed views about this.
Climate science professor Ralf Toumi from Imperial College London said it was dynamics in the atmosphere that created a rare window of opportunity for the multiple typhoons to form around the same time.
More than 170 people died in the storms, and 1.4 million residents were displaced.
An aerial view of submerged homes at a village in Ilagan, Isabela province in the Philippines, on Nov 18, 2024, due to continuous heavy rain from Super Typhoon Man-yi.
PHOTO: AFP
A stationary and persistent atmospheric wave – like a chain of regions with high rainfall – led to the typhoon cluster in the Philippines. This phenomenon is not clearly connected to ocean heat waves, and was thus hard to link to climate change, said Prof Toumi.
Affiliated to SMU’s Singapore Green Finance Centre, Prof Toumi was in town in July to give a lecture on the latest developments in climate science and policy.
Dr Samanta added that climate change did not directly cause the six consecutive typhoons, but record warm ocean water and large-scale atmospheric patterns steered them towards the Philippines.
He observed that marine heatwaves in the South-west Pacific stretched 40 million sq km in 2024.
Prof Switzer said: “While the six consecutive typhoons that struck the Philippines in 2024 may have been influenced by unusually warm ocean temperatures and conducive atmospheric conditions... attributing them directly to climate change remains one of the most complex and debated challenges in climate science.”
Can experts predict a typhoon’s timing and strength?
While scientists are good at forecasting a typhoon’s pathway, challenges remain in predicting storms that rapidly intensify right before landfall.
In 2023, Hurricane Otis unexpectedly intensified explosively into a Category 5 storm 24 hours before making landfall near Acapulco, Mexico. The authorities were expecting a weaker tropical storm.
Locals removing debris left by the passage of Hurricante Otis in Puerto Marques, Guerrero State, Mexico, on Oct 28, 2023.
PHOTO: AFP
The challenge lies with modelling the eye wall, the most powerful part of the typhoon, said Prof Toumi.
This is because the eye wall – where the strongest winds and heaviest rain occur – is only a few kilometres wide, but many weather models that scientists use to make forecasts divide the atmosphere into much larger grid cells.
Dr Samanta added that rapid intensification depends on small-scale processes inside the tropical cyclone – like bursts of thunderstorms near the eye – which are hard to detect and model.
Other research gaps are in predicting the levels of extreme rainfall brought by each typhoon, and how land terrain shapes the violent storms.
Dr Samanta said two recent typhoons, Podul in East Asia and Kajiki, caused widespread flooding after landfall, indicating a slower crawl over land and stronger rainfall depending on the terrain. These are processes that current models struggle to capture, he said.
“Forecasting tools still lack precision in estimating where and how much rain will fall, especially in complex landscapes,” he said.
“While these challenges cannot be solved overnight... Everyone has a role to play: conducting further studies, improving models, communicating societal impacts, and increasing funding for research and development,” added Dr Samanta.
In Vietnam, Typhoon Kajiki killed several people
The Philippines can get struck by 20 typhoons a year as it sits on the Pacific Typhoon Belt.
Reflecting on the aftermath of every typhoon season, Prof Toumi said: “In the Philippines, for example, it’s really an infrastructure (issue). There is a lot of building back, but not necessarily better.”
