AS Tropical Storm Soulik entered Thailand today (Sep. 20) Arcus clouds formed in Si Sa Ket province with the Meteorological Department warning 48 provinces plus Bangkok to brace for heavy rain and flash floods while waves in the Andaman Sea and upper Gulf of Thailand will rise higher than four metres in thunderstorms, TV Channel 7.
Arcus clouds are spectacular low-level, long and thin clouds associated with powerful thunderstorms. They are sometimes seen beneath Cumulonimbus clouds. Shelf clouds are attached to the storm cloud, whereas Roll clouds are a horizontal column separated from the storm cloud, the UK Met Office said.
When a cold downdraft from a Cumulonimbus cloud reaches the ground, the cold air may spread rapidly along the ground, pushing existing warm moist air upwards. As this air rises, water vapour condenses into the patterns associated with Arcus clouds. The new cloud may roll if it experiences different wind directions above and below.
These clouds are associated with strong gusty winds, heavy rain or hail showers as well as thunder and lightning.
This image of an Arcus cloud released by the Disaster Response Association of Thailand was taken at Dan subdistrict, Rasi Salai district, Si Sa Ket province.
The Thai Meteorological Department said Soulik entered Thailand at 10 a.m. this morning and now covers the Northeast with the centre being Phon Sawan district, Nakhon Phanom province, where the maximum wind speed is approximately 55 kilometres an hour.
This storm is moving westwards at approximately 15 kilometres an hour. It is expected to weaken into a low-pressure area this afternoon.
The North, Northeast, Central region including Bangkok and its vicinity, the East and the South will experience heavy to very heavy rain with strong winds. People should beware of flash floods, forest runoffs, especially on hillsides, near waterways and lowlands.
CAPTION:
The Arcus cloud photographed in Si Sa Ket. Photo: Disaster Response Association of Thailand
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