A hot June
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     The weather of June 2013 was hotter than usual. The mean temperature of the month was 28.2 degrees, 0.3 degrees above the normal figure of 27.9 degrees. There were five Very Hot days (daily maximum temperature of 33.0 degrees or above) in the month, about four days more than normal. The monthly maximum temperature of 34.2 degrees recorded on June 20 was the fifth highest for June on record. The monthly total rainfall of 438.6 millimetres was slightly below normal. The accumulated rainfall since January 1 was 1337.1 millimetres, about 22 per cent above the normal figure of 1096.8 millimetres for the same period.

     Under the influence of the anticyclone aloft over southern China, the weather in Hong Kong was sunny and very hot for the first three days of June 2013. Affected by the confluence of a southerly airstream over western Guangdong and an easterly airstream along the coast of southeastern China, local weather turned showery with a few thunderstorms from June 4 to 6. Despite still some showers, local weather improved on the ensuing two days with sunny periods. A trough of low pressure developed over the coastal areas of Guangdong on June 9.  Under the influence of the trough of low pressure, it was cloudy with showers and a few squally thunderstorms in Hong Kong on June 9 and 10. The trough of low pressure moved across the coast of Guangdong and entered the northern part of the South China Sea on June 11. Local weather deteriorated further on that day with heavy thundery showers. More than 50 millimetres of rainfall were recorded over widespread areas, and the rainfall of urban areas, Tseung Kwan O and Sai Kung even exceeded 100 millimetres.

     Affected by a broad area of low pressure over the South China Sea, it was mainly cloudy with a few showers on June 12 and 13. Under the combined effect of the broad area of low pressure and the ridge of high pressure over southeastern China, local weather became windy with heavy rain on June 14. While the area of low pressure moved towards Hainan Island on June 15, it remained cloudy with occasional heavy rain in Hong Kong on that day. With the area of low pressure moving further westward and weakening, the heavy rain eased off gradually the next day. There were sunny periods apart from a few showers and isolated thunderstorms on June 17 and 18.  

     Dominated by the anticyclone aloft over southern China, local weather became generally fine and very hot on June 19 and 20 with temperatures at the Hong Kong Observatory rising to a maximum of 34.2 degrees on June 20, the highest of the month. Meanwhile, a tropical depression formed over the South China Sea intensified into a tropical storm on June 21 and was named Bebinca. As Bebinca gradually edged closer to the South China Coast, local winds strengthened and the weather turned from sunny and very hot to cloudy with a few squally showers in the afternoon on June 21. On June 22, Bebinca moved across Hainan Island and the associated outer rainbands continued to bring squally showers to the territory. Local winds moderated gradually when Bebinca moved further away from Hong Kong during the day.  

     An active southwesterly airstream and a trough of low pressure affected the South China coastal areas on June 23 and 24 respectively, bringing mainly cloudy and showery weather to Hong Kong. The showers were particularly heavy on the morning on June 24 with more than 100 millimetres of rainfall generally recorded over the New Territories, Lantau Island and the northern part of Kowloon which necessitated the issuing of the Red Rainstorm Warning by the Observatory on that morning. Under the prevalence of the southwest monsoon, it was hot with sunny periods and a few showers from June 25 to 27. Dominated by the subtropical ridge, local weather remained generally fine apart from isolated showers for the next two days.  With the abundance of sunshine, it was fine and very hot on the last day of the month.

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

     Details of the issuance and cancellation of various warnings/signals in the month are summarised in Table 1. Monthly meteorological figures and departures from normal of June are tabulated in Table 2.

Ends/Wednesday, July 3, 2013
Issued at HKT 20:17

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