Typhoon Toraji - the eighth storm in the South China Sea - is one of four storms that appeared simultaneously in the northwest Pacific Ocean and the South China Sea in November. The other three are Yinxing, Usagi and Man-yi. This is the first time that four storms have appeared in this basin since data began in 1961.
SCMP interviewed typhoon experts to analyze the reasons for the late arrival of typhoons and the possibility of more frequent typhoons in November.
The plausible explanation for late storms like Typhoon Toraji in the South China Sea is that sea surface temperatures in the Pacific Ocean and the South China Sea remain warm even though it is already November, said Leung Wing-mo, former assistant director of the Hong Kong Observatory.
Tropical storms require a minimum sea surface temperature of 26 degrees Celsius to form, he pointed out. Temperatures off the coast of the Philippines are currently estimated to be between 28 and 29 degrees Celsius.
"These seas have stored a huge amount of heat and energy over the long summer. Global warming is also a contributing factor, making the ocean retain more heat," he said.
Typhoon experts from the Hong Kong Observatory (China) shared that the sea surface temperature this year and last year both broke records. Such warm sea water is enough to provide energy for typhoons to form.
The frequency of typhoons is related to the wind currents in the atmosphere. "Typhoons are like small boats drifting along these wind currents. These wind currents can be 1,000km to 2,000km in diameter, while a typhoon is only a few hundredkm in size," said Leung Wing-mo.
Meanwhile, Olivia Lee Shuk-ming, a senior scientist at the Hong Kong Meteorological Observatory (China), pointed out that this year, the subtropical high pressure band is stronger than usual and further north than usual.
“This has led to more tropical storms in the northwestern Pacific Ocean than in previous Novembers. The storms are spaced about 10 to 15 degrees longitude apart, allowing them to maintain their intensity and continue to strengthen independently,” she said.
Typhoons are common in November, according to typhoon expert Leung Wing-mo. One of the strongest typhoons ever recorded was Super Typhoon Haiyan, which devastated the Philippines in November 2013.
The Atlantic Ocean is also experiencing very warm sea surface temperatures, leading to many tropical depressions forming and leading to quite strong hurricanes hitting the US.
