Shamal dust and the 48-hour algae window
The shamal is the north-westerly wind that pushes down the Gulf, most intensely in early summer and in shorter winter bursts, and it is the single most predictable cause of green pools in the Emirates. The dust it carries is not inert: it brings phosphates and organic matter that feed algae, and a heavy storm can seed a warm, marginally chlorinated pool so effectively that visible bloom appears within two or three days.
The response window is short. Within a day of a major dust event the pool should be skimmed, the walls and floor brushed to lift settled dust before it binds to surfaces, the skimmer and pump baskets emptied, and the filter run extended. A preventive shock dose after a bad storm is cheap insurance; a green-to-clean recovery a week later is a multi-visit job involving heavy chlorination, flocculant, vacuuming to waste and sometimes a filter media change.