 |
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
 Typhoons necessitating the issuing of the Hurricane Signal No.10 It is not very often that one sees the issuing of the ultimate tropical cyclone warning signal of No. 10. When this signal is issued, it means that winds of hurricane force (i.e.118 km/h or more) are expected to affect the territory. Since hurricane force winds are largely confined to a relatively narrow strip around the eye wall of a typhoon, it would normally require a storm of typhoon status to pass fairly close to (say, within100 km of) Hong Kong. This is commonly referred to as a "direct hit". Considering Hong Kong is such a small target along the long coastline of eastern Asia, one finds it not surprising that only a dozen or so of typhoons have managed to score a direct hit in the post Second World War years, even with an average production rate of 16 typhoons per year over the South China Sea and the western North Pacific. From 1946 onwards, only 13 typhoons succeeded in issuing the No. 10 signal. The early 60s was a busy time for the No. 10 signal. It averaged once a year between 1960 and 1964, with 1964 being the special year when the signal was issued twice. Since those hectic days, the frequency was reduced to once in every three or four years.The 1980swas a relatively quiet decade with the No.10 issued only once. The 1990swas another quiet decade in which one had to wait till 1999 before seeing the first No.10 be issued. Of all the typhoons since 1946 for which the No. 10 had to be issued, Alice in 1961 and Shirley in 1968 crossed the Hong Kong Observatory. York in 1999 had the No.10 in force the longest - 11 hours. In terms of ferocity,Wanda sets the record. As the eye of Wanda passed over the territory, the barometer plunged to the all-time low of 953.2 hpa on 1 September 1962. Hourly mean winds of 133km/h and gusts of 259 km/h recorded in the harbour as well as gusts of 284 km/h recorded at Tate's Cairn during the passage of Wanda are records yet to be broken. The closest approach of Wanda coincided with the high tide and caused severe flooding in low-lying areas. Water level in the Tolo Harbour was as high as 5.4 metres above chart datum as compared with the normal high tide of 2.2. metres. Damage due to the tidal surge was particularly severe at Sha Tin and Tai Po.
|
 |
|
|
|