Meteorologists around the world are currently looking at the forecast for the Sahara Desert, one of the driest areas on the planet, because something unusual is about to happen: heavy rain.
Beggar
The latest forecasts from numerical models indicate that the Sahara, known as one of the driest places on Earth, may witness a unique event in the coming days and weeks, as data indicates large amounts of rainfall.
Accumulated rainfall can reach more than 500% of the historical average rainfall for August and September, an extremely rare occurrence in the region, which occurs, on average, once every decade.
Experts estimate that this exceptional rain event in the region could be an indication of unusual disturbances in the atmosphere and a change in global climate patterns at a time when the planet is experiencing accelerated global warming, with higher temperatures retaining more moisture in the atmosphere.
The Sahara Desert is one of the driest places on Earth because it receives very little rainfall each year. It is the largest and hottest desert in the world, stretching from the Atlantic Ocean in the west to the Red Sea in the east. It covers an area of more than 9.2 million square kilometers.
Far Northern Tropical Instability Belt
The rain in the desert will be directly related to the northward movement of the so-called Intertropical Instability Zone (ZCIT), which causes rain and storms. The Intertropical Convergence Zone (ITCZ) is essentially a belt of clouds and rain that runs around the entire equator, meaning that the trade winds from both hemispheres meet at this point, creating an upward movement of winds and the formation of rain clouds.
Wikimedia
Tropical winds from both hemispheres meet near the equator, creating an upward movement in the atmosphere that produces clouds, storms and rain. The region is very important because it affects the climate and rainfall in the tropics, and can also influence the formation of tropical storms.
Rainfall in the Sahara depends on changes in the integrated industrial commercial zone, as its movement northward in some seasons can bring rare rains in the interior of the Sahara, as expected in late August and September.
Rainfall up to 1000% above normal
Model forecasts suggest that the Sahara will receive much more rainfall than the annual average in the coming weeks, in areas that are not accustomed to it. While this may not seem like much compared to historical averages, in some areas the amount of rainfall expected in a few days will be equivalent to years.
ECMWF
Precipitation anomaly forecasts indicate that much of the Sahara Desert will experience widespread, well above-normal rainfall anomalies over the next two weeks and possibly beyond, potentially reaching maximums of 500% of the annual mean and over 1,000% of normal rainfall in central areas.
An extremely rare event with implications outside Africa.
More than half of the Sahara Desert receives less than 25 mm of rainfall throughout the year, but as tropical instability moves north, many areas may receive more than 1,000% of the annual average, and some will reach the maximum.
Data from the model reanalysis indicate that in August, in the last half-century, the Sahara region has had only four years with accumulated precipitation significantly above climatological averages, that is, the events occurred within a decade of each other.
Experts estimate that this very rare period of rain in the Sahara Desert could be “a sign that something may be changing in the Earth's climate system, indicating an unusual state in the atmosphere,” possibly linked to climate change.
As the tropical instability moves further north than usual in the coming days and weeks, the high tropical cyclone activity in the North Atlantic is unfavorable, and in the same way, conditions are unfavorable for more widespread and heavier rainfall in the Brazilian Amazon with extreme heat and worsening drought.
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