Ideal brew of conditions fuels Molave’s monstrous strength: experts

By Huu Nguyen   October 27, 2020 | 03:00 am PT
Ideal brew of conditions fuels Molave’s monstrous strength: experts
Satellite image of storm Molave. Photo courtesy of the U.S.'s National Oceanic and Atmospheric Administration.
Warm sea surface temperatures, weakening high-pressure cold air and the absence of obstacles on its path make Molave potentially the most powerful storm to impact Vietnam this year.

Storm Molave, the ninth storm to appear on the South China Sea, which Vietnam calls the East Sea, this year, has been classified as either a Category 1 or Category 2 typhoon in accordance with the Saffir-Simpson hurricane wind scale, said Nguyen Ngoc Huy, an independent forecaster.

The Saffir-Simpson scale classifies storms with sustained wind speeds between 119-153 kph as Category 1, while those with sustained wind speeds at 154-177 kph are classified as Category 2.

Conditions contributing to its ferocious strength include unobstructed movement upon entering the East Sea, warm sea surface temperatures of 27-28 degrees Celsius near coastal regions following weeks of sunny days, weakening high-pressure cold air that lessens its impact on Molave, and left-behind moisture of now-devolved Storm Saudel, according to Huy.

"Thanks to these advantages, Molave’s wind speed at its center could reach 150 kph as it travels past the northern areas of Spratly Islands," he said.

By 7 a.m. Tuesday, Molave had developed into a Category 3 typhoon with a sustained wind speed of 195 kph. Such a powerful tropical cyclone is a rare occurrence on the East Sea, Huy said. Once it is located about 200 km away from shore, Molave is expected to weaken into a Category 2 with a sustained wind speed of 165 kph, and is likely to maintain its power until it makes landfall in Binh Dinh, Quang Ngai and Quang Nam, he added.

Molave would make landfall early Wednesday morning, at around 5-7 a.m., Huy anticipated. Its eye would most likely be located over Quang Ngai, leaning a bit to the west-northwest of the province’s southern area. Due to its large radius, Molave might also make direct landfall on Binh Dinh and Quang Nam, which would see wind speeds at similar levels as they are recorded at the storm’s center, according to Huy, who holds a PhD in environmental studies from Kyoto University with a focus on disaster risk management and climate change adaptation.

Once Molave makes landfall, wind speeds at its eye are expected to reach around 130-165 kph. The storm would trigger high waves of eight to nine meters near the coast. Very strong winds should be expected in a 100-200 km radius from the storm’s eye, which would encompass regions like Da Nang, Kon Tum and northern areas of Phu Yen, while strong winds should be expected in a 250-300 km radius, encompassing regions like Hue and Quang Tri.

Very heavy rains should be expected in localities from Binh Dinh to Quang Tri, especially in Quang Ngai, Quang Nam, Da Nang and Hue. Main areas of rainfall would slowly move towards Quang Binh and Quang Tri by Thursday, Huy predicted.

Monstrous power

Molave’s exceptional power level, compounded with high tides, would trigger high waves capable of "lifting a large ship from the sea onto the shore," Huy said.

"This storm’s power is monstrous. Low-grade houses, especially those which were recently flooded and those lying in wind-prone areas, are highly likely to have their roofs blown away or be collapsed entirely. So people must not take shelter from the storm in low-grade houses," he warned.

With a gust speed of 150 kph near the shore, Molave’s power is comparable to historically powerful cyclones like Xangsane, which made landfall in Da Nang in 2006, and Damrey, which hit Nha Trang in 2017. Xangsane killed 71 people while Damrey claimed at least 106 lives, not to mention causing severe damage to infrastructure and properties.

Le Thi Xuan Lan, former deputy head of the forecasting division of the Southern Regional Hydro-Meteorological Center, said Molave entered the East Sea with a trajectory different from Saudel’s, allowing it to travel past sea regions with warmer surface temperatures.

As such, Molave would be provided with more power, Lan explained. Storm Saudel began as a tropical depression near the Philippines and devolved back into a tropical depression Sunday afternoon upon approaching central Vietnam.

By the time Molave entered the area, cold air from the north had already leaned towards eastern regions of China, which means Molave is not too weakened by the cold air. Constantly provided with fuel by the warm sea surface on its unimpeded movement path, Molave traversed quickly across the sea as it heads towards Vietnam, Lan said.

Tran Quang Nang, head of the weather forecast department of the National Center for Hydro-Meteorological Forecasting, said Molave is the strongest storm to appear on the East Sea this year. It possesses three characteristics that make it especially dangerous: fast movement, high power and a wide area of effect, he added.

With its rapid speed, Molave could impact coastal areas very early on, according to Nang. As soon as Tuesday afternoon, strong winds could already be picked up at sea, before the storm unleashes its full power on central and southern parts of central Vietnam starting Wednesday night. Strong winds, heavy rains and risen sea levels should be expected, bringing with them flooding and landslide risks in coastal and riverine areas, he added.

"This is a very powerful storm. The entire central area of the East Sea, from the northern parts of Spratly Islands to the southern parts of Paracel Islands, would be the storm’s center stage," Nang said.

As Molave closes in on Vietnamese shores, it would maintain its formidable power, causing strong winds in sea areas between Da Nang and Phu Yen, he added.

At 3 p.m. Tuesday, Molave is located around 390-580 km from the central coast between Da Nang and Phu Yen, with a maximum wind speed of 165 kph, according to the National Center for Hydro-Meteorological Forecasting.

It is expected to bring rainfall of up to 700 mm in several regions from Tuesday night to Saturday.

Before entering the East Sea, the storm had wrecked havoc in the Philippines, killing at least three and making dozens go missing, the country’s National Disaster Risk Reduction and Management Council said Tuesday.

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