The city should be ready for unstable weather earlier next week with heavy rainfall and thunderstorms possible because of the emergence of a southwest monsoon.
The weather watchdog said on Thursday that showers would be heavy at times with squally thunderstorms early next week, under the influence of a broad low-pressure trough.
Showers would persist into the middle to latter parts of next week, under the influence of a southerly airstream, the forecaster said.
The forecaster said further that a dry easterly airstream was bringing generally fine weather to the coast of Guangdong province on Thursday.
On Friday and Saturday, sunny periods are expected while more showers will follow for few days. Temperatures will range between 24 and 29 degrees Celsius, forecaster said.
Hong Kong Observatory stated that the southwest monsoon in the South China Sea typically arrives around May 16 to 25. From a climatological perspective, the monsoon is an important part of seasonal variations. It marked the start of the rainy season.
The basic driving force of the southwest monsoon is large-scale differential heating between land mass and the ocean.
Starting from April, as the Asian continent heats up faster than its neighbouring oceans, a low pressure centre forms.
Computer models predict that during the weekend, southwest winds in the lower levels of the South China Sea will gradually establish themselves.
The northern part of the South China Sea will also be gradually influenced by southerly wind, providing favourable thermal and moisture conditions for convection development along South China coastal areas and the northern part of the South China Sea.
The Observatory said that if other atmospheric conditions were suitable, there would be a chance of triggering heavy rainfall.
香港天氣將變得更加不穩定，有大陣雨和雷暴
由於西南季風的出現，該市應該為下週早些時候不穩定的天氣做好準備，可能會出現強降雨和雷暴。
氣象監督機構週四表示，受廣泛低壓槽的影響，下週初將有陣雨，並伴隨狂風雷暴。
預報員稱，在偏南氣流的影響下，陣雨將持續到下週中下旬。
預報員進一步表示，週四一股乾燥的偏東氣流為廣東省沿海帶來整體晴朗的天氣。
週五和週六，預計會有陽光明媚的時期，而接下來的幾天將會有更多陣雨。 預報員稱，氣溫將在攝氏 24 至 29 度之間。
香港天文台表示，南海西南季風通常於5月16日至25日左右到來。 這標誌著雨季的開始。
西南季風的基本驅動力是陸地和海洋之間的大範圍加熱差異。
從四月開始，隨著亞洲大陸升溫速度快於鄰近海洋，低壓中心形成。
電腦模型預測，週末期間，南海低層將逐漸形成西南風。
南海北部地區也將逐漸受到南風影響，為華南沿海地區和南海北部對流發展提供有利的熱濕條件。
天文台表示，若其他大氣條件合適，有機會引發強降雨。
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