Arab Weather - Sinan Khalaf - The weather forecast staff at the Arab Regional Weather Center warned of sand storms and dust waves that may be caused by downward winds associated with thunderstorms in parts of the Kingdom on Thursday and Friday, warning of the danger of low horizontal visibility and possibly its absence in some periods, according to Cloud strength, and the alert includes all of the eastern parts of the Makkah Al-Mukarramah region, in addition to Hail and Al-Qassim, and an extension eastward towards Hafr Al-Batin, Al-Qasumimah and parts of the northern border region.
Sometimes sandstorms are formed as a result of what is known climatically as “downward winds” , which are strong winds that fall from the cumulus cloud and strike the ground vertically.
The downward wind arises due to the difference in the density of the air below the cumulus cloud. When it rains, the raindrops evaporate under the cumulus cloud before it reaches the ground, so the air in that part cools dramatically and becomes denser and heavier than the air around it, and it falls as a descending mass in the form of winds called “the downward wind.” And it hits the earth with a destructive force sometimes and at a speed that may exceed 200 km / h, which leads to the formation of dust waves whose density and strength vary according to the strength and intensity of the winds descending from the cumulus cloud.
Regarding this, experts cautioned:
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