From April 15th to April 17th, local time, the vicinity of the Persian Gulf was flooded by dense lightning, and a number of huge towering thunderstorm clouds rose into the sky, and many countries in the Middle East centered on the Strait of Hormuz suffered unprecedented super rainstorms, and the UAE metropolis Dubai was ravaged by 4 consecutive rounds of heavy rainfall in 24 hours, and the precipitation at Dubai Airport exceeded 160 mm in 24 hours, and the precipitation for nearly two years was completed in 1 day, breaking the local record.
In the face of unprecedented rainfall, Dubai has been severely waterlogged, many buildings have leaked, traffic has been completely paralyzed, and even the airport has been transformed into a seaport, with planes passing through the water. Dubai is not the most rainy place in the Middle East, the mountains at the junction of the UAE and Oman rained 200~302 mm in 3 days, and the daily rainfall reached 1,000 times or infinity times of the local rainfall in April, reaching 2-4 times the annual rainfall. As the thunderstorm clouds moved eastward, heavy precipitation also hit the southeastern coast of Iran and the western coast of Pakistan during the day on the 17th, flash floods broke out in many places, and many deserts turned into large lakes. For the Middle East, this torrential rain is a once-in-a-century experience.
Because the torrential rain was so bizarre that the local area had never experienced it before, many people believed that it was caused by artificial rainfall. The UAE's National Meteorological Center immediately came out to deny it, saying that there was no artificial rainfall operation either before or when the rainstorm came. In fact, no matter what the UAE Meteorological Department says, it is unlikely that such extreme storms and rains could have fallen from the so-called artificial rainfall. According to the current level of science and technology, we can only help the rain clouds to work harder when there are precipitation conditions, so that they can shake down more raindrops. Strictly speaking, this cannot be called artificial rainfall, but artificial rainfall.
So, what caused the heavy rains in Dubai and other places, and what will be the after-effects?
First of all, the direct cause. This heavy rain is typical of severe convective weather, not caused by a typhoon (called a cyclonic storm in the Arabian Sea), but by a cloud mass of severe convection. Since April 15, with the depth of the Arabian Vortex downward, the high-altitude cold air thrown out by the Arabian Sea vapor and the cold vortex converged near the Persian Gulf, and the strong thunderstorm clouds rose into the sky, and the cloud top bright temperature was once lower than -80 degrees, close to the cold cloud cover temperature of super typhoon Meranti, and the local meteorological station issued a squall line and hail forecast, which is rare in a century in the tropical desert area.
Secondly, the circulation cause. In April of previous years, the desert areas of the Middle East were all sunny skies, extremely hot, and the precipitation in the whole month was infinitely close to zero, why can the Arabian Sea vapor go north in April 2024, and such a strong cumulonimbus cloud can be produced? This is because in April 2024, the westerly wind belt in the northern hemisphere is seriously southerly, and in the late and middle of April, the westerly wind belt will lay two eggs in a row, and two extremely deep low vortices will break into the Sahara Desert in Africa and the desert areas of the Arabian Peninsula.
Prior to the heavy rains in Dubai, the African vortex had already brought an extremely rare cold wave to the Sahara Desert, with Algeria plummeting from over 40 degrees to below 20 degrees, hail and force 11 winds. It is under the influence of the Arabian Vortex that the Arabian Sea vapor can move northwards and meet with the cold air above Dubai, causing violent storms and rains. This is a weather situation that has not been seen in a century.
Third, the climatic context. First, 2023 is an El Niño year, and in the years after El Niño, the southern pressure of the subtropical jet in the spring of the Northern Hemisphere, that is, the westerly wind belt is prone to southerly and the depth of the vortex is cut off and enters the low latitude region; second, from the winter of 2023 to the spring of 2024, the SST in the North Atlantic is also significantly higher, which stimulates the anomalous wave train from the tropics to the middle and high latitudes, which aggravates the southerly situation and oscillation of the westerly wind belt in the Northern Hemisphere;
Third, since the spring of 2024, the temperature, ground temperature, and sea temperature in the northern hemisphere have been seriously high, and the atmospheric energy is very abundant. When the eggs are cut under the depth of the westerly wind belt, and the cold vortex enters the low latitude, the collision between cold and warm will be very violent, and extreme winds, heavy rains, hail and so on are prone to occur.
The heavy rain in Dubai has passed, but the circulation situation and climatic background that caused the heavy rain in Dubai still exist. With the eastward movement of the Arabian Vortex and the dissipation of energy, the westerly wind belt of the future continent will not only not converge to the north, but will expand southward, and the subtropical high will be forced to retreat southward. In fact, from April 17 to 18, the southward expansion of the westerly wind belt of the mainland has already occurred, and the rain belt in the south of the Yangtze River has shifted to South China. From the middle of the night on April 17, a huge squall line up to hundreds of kilometers was assembled and formed in Guangxi, and then swept eastward across Guangxi and Fujian, and the Pearl River Delta was overwhelmed by dark clouds and strong winds around noon today, with maximum gusts of 11.
In the southwest, the cold and warm air began to fight fiercely again, Chengdu became the second rainstorm center after Guangdong, and after nightfall, a large hail fell in Guizhou; the rain front even went north all the way to the edge of the monsoon region, Ningxia was hit by a rare heavy rain in April, and Yinchuan had the third highest daily rainfall in April as of 20 o'clock. With the continuous tenacious southerly southerly westerly wind belt, Guangxi, Guangdong, Fujian, Guizhou, Jiangxi, Hunan and other places will become the main battlefield of the fierce convergence of cold and warm air masses in the future, especially in Guangdong, Guangxi, the squall line on April 18 is just the beginning, and there will be a lot of strong convective weather such as strong winds, heavy rains, thunder and lightning in the future, and the peak of the real rainstorm has not yet arrived.