The Weather of September 1999

    September was wetter than normal. The monthly rainfall of 365.7 millimetres was 22 per cent higher than the normal figure. The total rainfall since 1 January was 2 041.7 millimetres, two per cent above the normal for the same period.

    Three tropical cyclones affected Hong Kong in the month and the Hurricane Signal, No. 10, was hoisted during the passage of Typhoon York. This was the first time since 1983 that the Hurricane Signal was hoisted. The Red Rainstorm Warning Signal and the Landslip Warning were issued on 16 September.

    It was fine on the morning of 1 September. Isolated thunderstorms developed in the afternoon and a fisherman was struck by lightning near Lei Yue Mun. Hazy conditions occurred the following morning and there were isolated showers in the afternoon. It was again hazy on the morning of 3 September but the weather became fine and hot in the afternoon with temperatures rising to 32.8 degrees, the highest in the month.

    As Tropical Storm Wendy made landfall near Shanwei early on 4 September, local weather turned cloudy with a few showers. Isolated thunderstorms developed on 5 September. However, it was mainly fine apart from some isolated showers for the next few days. For details please refer to the report on Wendy.

    The weather became fine and hot on 10 September. Hot weather persisted the next few days and it was reported that two hikers died of heatstroke on 12 September. Hazy conditions were observed at the airport on 13 and 14 September. Temperatures rose to 32.8 degrees again on 14 September.

    On 15 September, Typhoon York approached Hong Kong from the southeast and weather became cloudy to overcast with some rain patches. Strong winds started to affect offshore areas in the evening. York crossed the southwestern part of Lantau around noon next day. Winds of hurricane force and heavy rain buffeted the territory resulting in the death of two people. The daily rainfall of 276.0 millimetres recorded on 16 September was the second highest for September. Direct economic loss due to York was estimated at several billion dollars. For details please refer to the report on York.

    As York moved away, rain eased off and sunny periods developed on 18 September. Isolated heavy showers returned the next day. It was hazy on the morning of 20 September and there were isolated thunderstorms in the afternoon.

    A northeast monsoon brought dry weather to the southern China coastal areas on 21 September. It became fine with long sunny periods on 22 September.

    Fine weather persisted until 25 September when Severe Tropical Storm Cam approached from the southeast. Cam swept across the New Territories the next day. Gales and a few squally showers were experienced. However, damage was minimal. Temperatures dropped to 22.8 degrees that morning in heavy showers, the lowest in the month. Weather remained mainly cloudy. For details please refer to the report on Cam.

    Easterly winds strengthened offshore on the evening of 27 September as the northeast monsoon intensified, bringing along some rain patches. Cloudy and rainy weather continued the next day. It became fine and sunny on 29 September. Fine weather prevailed till the end of the month.

    Six tropical cyclones occurred in the South China Sea and the western North Pacific in the month.

    During the month, a total of 30 aircraft was diverted due to adverse weather.