Weather of Arabia - Sinan Khalaf - alerted the weather forecast staff at the Arab Regional Weather Center of sand storms and dust waves that may be caused by downward winds associated with thunderstorm clouds in parts of Riyadh and the eastern region during the coming days, especially on Thursday, warning of the danger of low horizontal visibility And perhaps its absence in some periods, according to the strength of the clouds.
Sandstorms are sometimes formed as a result of what is known climatically as " downward winds ", which are strong winds descending from the cumulus cloud and hitting the ground vertically, as a result of which a wave of dust is formed that spreads in a circular manner and expands and takes the form of a huge majestic brown cloud.
Downward winds arise due to the difference in air density below the cumulus cloud. When it rains, the raindrops evaporate under the cumulus cloud before reaching the ground, so the air in that part cools down significantly and becomes denser and heavier than the air around it, so it falls as a downward mass in the form of winds called " downward winds ". And it strikes the earth with destructive force sometimes at a speed that may exceed 200 km / h, which works to form dust waves whose density and strength vary according to the strength and intensity of the winds descending from the cumulonimbus cloud.
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