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The weather of July, 2006, was marked by heavy rain and severe thunderstorms associated with an active southwest monsoon that affected the south China coast. The total rainfall of 569.2 millimetres in the month was 245.7 millimetres above the normal figure. The accumulated rainfall since January 1, was 1,771.5 millimetres, 35% more than the normal of 1,316 millimetres for the same period.
Apart from some isolated showers, it was fine and hot in the first four days of the month. Under the influence of the southwest monsoon, the weather was characterised by periods of sunshine and some showers from July 5 to 10.
Affected by a weak trough of low pressure along the south China coast, there were scattered showers and squally thunderstorms on July 11. The weather turned fine the following day. When Severe Tropical Storm Bilis moved near Taiwan on July 13, it was very hot in Hong Kong and the maximum temperature shot up to 34.0 degrees, the highest in the month. The outer rainbands of Bilis brought scattered squally showers to Hong Kong on July 14. Showery weather continued on July 15 as an active southwest monsoon set in. On the early morning of July 16, the weather deteriorated further with heavy downpour and squally thunderstorms. During the torrential rain, more than 150 millimetres of rainfall was recorded in Hong Kong Island, Kowloon, Cheung Chau and Tseung Kwan O, necessitating the issuance of the Black Rainstorm Warning. Between 2am and 3am, a record-breaking 115.1 millimetres of rainfall was registered at the Hong Kong Observatory Headquarters, breaking the previous record of hourly rainfall of 109.9 millimetres recorded from 6am to 7am on May 8, 1992. The weather stayed cloudy with a few showers on July 17.
Sunny weather returned on July 18 when a ridge of high pressure dominated over southeastern China. Apart from a few isolated showers, fine and hot weather prevailed in the next five days. Under the influence of the subsiding air ahead of Typhoon Kaemi, it was very hot and hazy on July 24 and 25. The high daytime temperatures also led to development of severe squally thunderstorms in the afternoon of July 24. Hail was reported at Sai Kung in the thunderstorms.
The weather became cloudy with some showers on July 26 as affected by the rainbands of Kaemi. Hong Kong came under the influence of an active southwesterly airstream on July 27. It was rainy with scattered squally thunderstorms. Unsettled weather persisted in the following two days.
Local weather improved on July 30 under the influence of a ridge of high pressure over southeastern China. It was sunny on the last day of the month.
Four tropical cyclones occurred in the western North Pacific and the South China Sea in the month.
Details of the issuance and cancellation of various warnings/signals in the month are summarised in Table 1.1. Monthly meteorological figures and departures from normal of July are tabulated in Table 1.2.
Ends/Wednesday, August 2, 2006
Issued at HKT 17:07
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