Why does it not rain the Sahara desert?

The Sahara Desert is very dry and even extremely dry because the desert is located in the subtropics, near the tropics where there is a semi-permanent, subtropical high pressure belt, called the subtropical ridge that is present in the subtropical latitudes, also known as the horse latitudes. The subtropical ridge is a belt of large-scale descending, sinking dry air which brings clear skies, sunny and dry weather to the region. The subtropical ridge is directly formed by the general atmospheric circulation, more accurately by the Hadley Cell. The subtropical ridge is the major factor that explains the aridity of the Sahara Desert. The subtropical ridge produces the trade winds, which are the prevailing winds found in the intertropical zone which blow from the northeast to the southwest in the Northern Hemisphere. The trade winds blow from the subtropical ridge to the ITZC (Intertropical Convergence Zone which responds to a equatorial low pressure belt). The trade winds passes over the Sahara Desert and are a very dry since they come from directly from the subtropical high pressure systems, which allows to keep the desert dry since there are no source for taking moisture (continentality). The last factor that causes aridity in this desert is the rain shadow, for example the High Atlas Mountains, being the highest and the most important mountain range in the Sahara Desert block the most pat of the moisture from the winds blowing from the Mediterranean Sea to the Pacific Ocean : the cool, wet air from the sea becomes a hot, dry air that stagnates over the desert.