Riyadh was hit on March 10 by what many residents said was the worst sand storm in three decades, and it now appears that there may be more in the offing. A climate-change expert forecasts sudden and extreme weather changes in the weeks ahead, resulting in dust storms, particularly in the northern, central and eastern parts of Saudi Arabia. Caused by passing depressions or cyclones, these sharp fluctuations in the weather are expected to peak in April and consequently decline until May, said Dr. Mansour Almazroui who heads the Department of Meteorology at Jeddah's King Abdulaziz University. He is also associate fellow at the Climatic Research Unit, University of East Anglia, Norwich, United Kingdom. He said spring arrived in Saudi Arabia on Saturday, March 21, its astronomical beginning in the northern hemisphere when the Sun was right above the Equator and the day was as long as the night – the days gradually get longer from then on. Spring in Saudi Arabia is generally the transitional season when two air masses, cold and hot, collide to cause dust storms and rainfall. However, this time around, the frequency of dust storms will increase rapidly, “more than the years before,” Dr. Almazroui said. He attributed the expected spate of dust storms to mainly cyclones moving west to east and also the current drought in the country. Pressure and temperature gradients and active surface winds can churn up dust storms, he explained. In the weeks ahead, the likelihood of this happening is high “due to an encounter between southerly and hot south-easterly winds associated with an extension of the Red Sea trough – moving north and north east of Saudi Arabia – and cold north-westerly winds associated with the Mediterranean depressions – passing north of Saudi Arabia.” “These will result in convergence in a small localized region associated with updrafts and downdrafts, leading to dust permeating the upper atmosphere and possibly leading to precipitation and thunderstorms,” Dr. Almazroui said in an e-mail to Saudi Gazette. Moreover, the current drought conditions in Saudi Arabia could cause a reduction in water reserves and greenery in many places, thereby enhancing desertification. This dryness will reduce cohesion between fine sand particles and thereby increase the intensity of dust storms, particularly in the north, middle, east and other places in Saudi Arabia where surface winds are strong, he said. Dr. Almazroui expects the weather systems to stabilize and temperature to rise progressively as summer sets in. “This will be followed by a weakening of the Mediterranean depressions and a deepening of the Indian monsoon, which is characterized by droughts and increase in temperature, particularly by the end of July and August,” he said. Passing cyclone today On Monday, a cyclone over the Mediterranean Sea is expected to pass quickly over the northwestern region, raising the possibility of a small amount of rainfall, Dr. Almazroui said. On Tuesday, after the cyclone, an invasion of cold air is expected, affecting the northern, central and eastern parts of Saudi Arabia, he said. Sandstorms are also likely on Tuesday and Wednesday in the northeastern and north-central areas. Southerly wind speeds on Tuesday are 25-30 kmph in the north and 35-40 kmph in the Riyadh area – raising the chances of dust storms in the Riyadh and the eastern regions. Wind direction is expected to be northerly on Wednesday, when the weather should settle, though there is a chance of rain in the southern Riyadh region and the south-eastern and Qatar regions, Dr. Almazroui said.
