Why is Hong Kong so hot in October and will winter be warmer than usual?

Hong Kong’s exceptionally warm October weather is being driven by a combination of a super typhoon, El Nino and global warming, a climate expert has said, warning that higher-than-usual temperatures are likely to persist through the winter.

The warning came as autumn temperatures across the city topped 30 degrees Celsius (86 Fahrenheit) over the past few weeks.

Professor Amos Tai Pui-kuen, of the earth and environmental sciences department at the Chinese University of Hong Kong, explained on Wednesday that El Nino had altered typhoon paths and weakened the northeasterly winds that typically reach the city in autumn.

“A ‘super’ El Nino means that courses of typhoons would move more northerly … if and when typhoons do hit Hong Kong, because of the high sea level temperatures, there will be more heat and steam evaporating, which contributes to a stronger typhoon, too,” he said.

He added that El Nino had changed atmospheric circulation, weakening the autumn northeasterlies and reducing heat dissipation, leaving Hong Kong hotter.

Another factor was a super typhoon near Manila, Tai said. He explained that an anticyclone had formed over Hong Kong as part of the typhoon’s outer circulation, causing air to sink and winds to weaken, with sunshine becoming “particularly abundant”.

He added that global warming had also raised baseline temperatures.

A local green group and a leading meteorologist warned in July that Hong Kong should prepare for stronger storms and a warmer, wetter winter, as the current El Nino was likely to intensify into a super event.

Tai said temperatures would gradually fall as winter approached, but the season was likely to be warmer than in previous years because of the lingering effects of the “super” El Nino, which could last until spring.

Five hikers fell ill in separate incidents across Hong Kong on Monday as hot weather gripped the city on the final day of the Chung Yeung Festival long weekend. Some were airlifted to hospital by the Government Flying Service.

Conditions were hot and dry that day, with the maximum temperature reaching 32 degrees Celsius at the Hong Kong Observatory’s urban headquarters and several degrees higher in parts of the New Territories.

The Observatory forecast temperatures would reach 33 degrees on Friday before gradually falling below 30 degrees later the following week.