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Ambrose Li

Oscar Liu

With Tropical Storm Toraji edging closer to the Pearl River Delta, the Hong Kong Observatory issued the No 8 typhoon signal on Wednesday night, the latest such warning on record.
The timing surpassed Typhoon Pamela in 1972, for which the No 8 signal was in force on November 8.
Toraji is one of four storms to emerge simultaneously in the western North Pacific and South China Sea in November for the first time since records began in 1961.
The Post breaks down the causes of late typhoon occurrences and the likelihood of frequent storms in November.
1. Why is Toraji so late in the year?
Leung Wing-mo, a former assistant director of the Observatory, said one plausible explanation for such a late typhoon was that the sea surface temperature in the Pacific Ocean and South China Sea remained warm despite it being November.
Leung said tropical cyclones required a minimum sea surface temperature of 26 degrees Celsius to form, and he estimated that off the Philippine coast it now stood at about 28 to 29 degrees.
“The waters have stored vast amounts of heat and energy from the long summer,” he said. “Global warming is also a contributing factor, enabling them to stay warm.
“The sea surface temperatures this year and last year have all broken records in being very warm.
“Warm waters could provide enough energy for tropical cyclones to form. If the sea surface temperatures were too low, there would be no need to consider other factors.”
2. Why are storms so frequent in November this year?
Four tropical cyclones – Toraji, Yinxing, Usagi and Man-yi – simultaneously appeared in November in the northwest Pacific and the South China Sea, marking the first such occurrence since the Observatory began keeping records in 1961.
Leung said the frequency of storms had to do with steering currents in the atmosphere that were much larger than typhoons or tropical cyclones.
“Typhoons would be like small boats floating on the river of steering currents and be led by them. These currents could fetch 1,000km to 2,000km in diameter, but a typhoon is just several hundred kilometres in size,” he said.

Olivia Lee Shuk-ming, the Observatory’s senior scientific officer, said the subtropical high-pressure ridge was stronger than usual this year, and its position was also further north than normal.
“This has resulted in tropical cyclones appearing in the northwest Pacific at a more northerly latitude than in past Novembers,” she said.
“They are spaced about 10 to 15 degrees of longitude apart, allowing each of them to maintain their intensity and continue to develop independently.”
3. Do other regions have late typhoons?
Leung said typhoons in November were more common than one would think, pointing to one of the strongest storms ever recorded – Haiyan, which wreaked havoc in the Philippines in November 2013.
Over in the Americas, the Atlantic Ocean also had very warm sea surface temperatures, which gave the area a lot of tropical cyclones, and meant that those that hit the United States were quite powerful, Leung said.
4. Is it common to issue the No 8 signal late in the year?
Hong Kong has experienced several instances of the No 8 signal being in force in November.
One such occurrence was during Typhoon Pamela on November 5, 1954, which lingered for almost 14 hours. By 10.15am the next day it strengthened with the No 9 signal in force for almost five hours until 3pm. The typhoon weakened, with the No 8 signal in place for almost two hours until 5pm.
Another notable event unfolded on November 8, 1972, with the No 8 signal in force for 14 hours when another typhoon also named Pamela struck.
More recently, Severe Tropical Storm Nalgae on November 2, 2022, resulted in the No 8 signal lasting for almost 16 hours.


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Why is Hong Kong getting typhoons in November and are more coming late in year?

Pedestrians walk in Central under the Storm Signal No.8. Photo: Sam Tsang

It is not the first time for Hong Kong to experience a No 8 signal in November. Photo: Eugene Lee

Stormy times this week with (from left) Yinxing, Toraji, Usagi and Man-yi. Photo: Handout

Tropical Storm Toraji: Hong Kong issues T8 typhoon warning signal

The forecaster says winds will strengthen later in the day. Photo: Nora Tam

Toraji is expected to skirt within around 150km to the south of Hong Kong on Thursday. Photo: Nora Tam

Storm Toraji: Hong Kong may raise T3 typhoon signal on Wednesday afternoon

The Hong Kong Observatory will keep T1 in force until midnight on Wednesday. Photo: Nora Tam

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The forecaster says there will be sunny periods in the next couple of days but the weather will become unsettled by midweek. Photo: Sam Tsang

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Toraji is one of four storms to emerge simultaneously in November for the first time since records began in 1961


Toraji is one of four storms to emerge simultaneously in November for the first time since records began in 1961.


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Explainer | Why is Hong Kong getting typhoons in November and are more coming late in year?

Toraji is one of four storms to emerge simultaneously in November for the first time since records began in 1961

1. Why is Toraji so late in the year?