The Weather of June 2013

    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 5 Very Hot Days (daily maximum temperature of 33.0 degrees or above) in the month, about 4 days more than normal.  The monthly maximum temperature of 34.2 degrees recorded on 20 June was the fifth highest for June on record.  The monthly total rainfall of 438.6 millimetres was slightly below normal.  The accumulated rainfall since 1 January was 1337.1 millimetres, about 22 percent 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 4 to 6 June.  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 9 June.  Under the influence of the trough of low pressure, it was cloudy with showers and a few squally thunderstorms in Hong Kong on 9 and 10 June.  The trough of low pressure moved across the coast of Guangdong and entered the northern part of the South China Sea on 11 June.   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 12 and 13 June.  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 14 June.  While the area of low pressure moved towards Hainan Island on 15 June, 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 17 and 18 June. 

    Dominated by the anticyclone aloft over southern China, local weather became generally fine and very hot on 19 and 20 June with temperatures at the Observatory rising to a maximum of 34.2 degrees on 20 June, the highest of the month. Meanwhile, a tropical depression formed over the South China Sea intensified into a tropical storm on 21 June 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 21 June. On 22 June, 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 23 and 24 June respectively, bringing mainly cloudy and showery weather to Hong Kong.  The showers were particularly heavy in the morning on 24 June 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 in that morning.  Under the prevalence of the southwest monsoon, it was hot with sunny periods and a few showers form 25 to 27 June.  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 issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.6.  Monthly meteorological figures and departures from normal for June are tabulated in Table 2.