August 9 was previous mark for a first hit, but unofficial weather observers say a Signal No1 should have been hoisted in July
If nothing dramatic happens over the South China Sea today, Hong Kong will set a new weather record - the latest start to the typhoon season since detailed typhoon records began to be kept in 1946.
The latest start previously recorded was on August 9, 1998, when the strong-wind warning was hoisted with the approach of tropical depression Penny.
But the new record is being disputed by unofficial weather observers who stay the No1 standby signal should have been raised in late July when Typhoon Washi came within 400km of the city.
At least three tropical cyclones have strolled around the region this year, but none has affected Hong Kong. Instead, they headed to Taiwan, Japan or the mainland.
In normal circumstances, tropical cyclones affect the city from June to October, with most in September and about six in a season.
Earlier this year, the Observatory predicted that four to six typhoons would affect the city this season.
Clarence Fong Chi-kong, the host of the Weather Underground website, said yesterday he and other weather observers had doubts about the new record.
He said the periphery of Typhoon Washi in late July, which at one point lay 400km southwest of the city, had been gaining force and brought gusty wind and heavy rain.
'Perhaps there are some man-made factors involved over whether the warning signal was issued or not,' said Mr Fong, dismissing the record as having only statistical, rather than scientific, significance.
Observatory senior scientific officer Chang Wen-lam said there was no need to issue the signal as Washi was moving away from the city and heading to Hainan.
But he admitted fewer typhoons have been seen in the South China Sea this year, with only two - Roke and Washi - compared with the normal average of four.
Dr Chang said it was too early to note any trend, despite the fact that the Observatory had found a decrease of 0.8 per decade in the number of tropical cyclones in the South China Sea between 1961 and 2004. A decline of 1.4 per decade was also observed in the north-western Pacific for the same period.
'Every year the number of typhoons and when the season starts varies,' he said, adding that complex factors governed where a typhoon formed and its movement.
However, Mr Fong said the reduction could be due to intermittent changes in western Pacific air pressure, which could deflect the path of cyclones away from the South China Sea.
When the Pacific high pressure ridge extends into Taiwan or Fujian, cyclones usually reach the South China Sea, but a weaker ridge will deflect them, Mr Fong said.