The Weather of May 2006

    May 2006 was wetter than usual. The monthly rainfall of 431.5 millimetres was about 36 percent above the normal figure of 316.7 millimetres. The accumulated rainfall since the beginning of the year was 733.1 millimetres which was about 19 percent above the normal of 616.5 millimetres. Affected by the rainy weather, it was also less sunny in the month. The total bright sunshine duration of 122.2 hours was 31.6 hours below normal.

    It was mainly fine and hot on the first day of May. The weather deteriorated with heavy showers and thunderstorms on the next two days as Hong Kong came under the influence of a trough of low pressure over the south China coast. It remained cloudy with a few showers on 4 and 5 May.

    With the trough of low pressure dissipating, the weather improved and there were some sunny periods on 6 May. It was mainly fine and hot in the following six days. The temperature rose to 31.5 degrees on 8 May, the highest so far in this year.

    A cold front passed Hong Kong on 13 May. The temperature fell to a minimum of 20.5 degrees in the early morning of 14 May. The weather was mainly fine and dry in the following day. Meanwhile, Severe Tropical Storm Chanchu entered the South China Sea and intensified into a Typhoon. Chanchu moved north steadily towards the south China coast on 15 and 16 May. With the approach of Chanchu, the Hong Kong Observatory issued the Standby Signal No. 1 on 15 May and then the Strong Wind Signal No.3 on 17 May, the first time in this year. Locally, the weather became cloudy with scattered showers on 16 and 17 May. Winds also strengthened and occasionally reached gale force over offshore and on high ground on 17 May. Soon after Chanchu made landfall to the east of Shantou on the early morning of 18 May, local weather turned fine and remained so on the next day.

    The weather became cloudy again on 20 May as a trough of low pressure approached the south China coast from the northern part of the South China Sea. It was rainy with a few squally thunderstorms on the ensuing three days. The weather stayed cloudy with a few showers on 24 May.

    The clouds dispersed and there were sunny periods on 25 May. With the approach of a trough of low pressure from the north, the weather deteriorated gradually on 26 and 27 May. The trough of low pressure brought rainy weather to the territory on the last four days of the month.

    Only one tropical cyclone occurred in the western North Pacific and the South China Sea in the month.

    Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.5.  Monthly meteorological figures and departures from normal for May are tabulated in Table 2.