Most deserts are a result of the rainshadow effect, cold currents, the subtropical ridges, or a combination of those. Knowing this, how is the Somali desert caused?

It is notable since it has a desert climate close to the equator, which is known for being wet. Furthermore, it is on the East Coast of Africa, and Eastern Coasts within 0 to 45 degrees latitude are almost always wet.

I've searched and read about the rainshadow effect of the Ethiopian highlands causing the rainshadow effect. However, the trade winds go towards the East, which should make Somalia even wetter. I've read about the monsoon effect, which would explain the rainshadow effect... for the summer. In the winter, however, the wind should bring moist air back to Somalia. So if anything, Somalia should be a tropical Mediterranean climate. Reports say that entire years can go by without rain though.

In summary, my question asks for the cause(s) of the Somali desert being so dry and why it isn't a Mediterranean climate.

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    $\begingroup$ Any rain requires a moisture source. So the Western Indian Ocean has a unique coastal upwelling that brings up cooler waters from under the ocean surface. This ensures that SSTs remain below normals relative to elsewhere. Comparable to the East Pacific Cold tongue. $\endgroup$ – gansub Mar 13 at 2:45
  • $\begingroup$ en.wikipedia.org/wiki/…. $\endgroup$ – gansub Mar 13 at 2:51
  • $\begingroup$ I know you are asking about the winter monsoon(D J F) but during that time the Somali current moves S Westward. I don't think it disappears nature.com/articles/srep30137 - fifth most upwelling region in the world $\endgroup$ – gansub Mar 13 at 2:57
  • $\begingroup$ @gansub I certainly don't know much about the area, and thought cold SST might be a big factor, but AVHRR suggests SST in the 70s\80s now. And though surfaces obs seem hard to come by, found HCMF (Bosaso) on the coast had Td of 75F (24C) today and plenty of time during the year typically >= 70F (21C). So it seems it must be something more dynamical, and surprise the seabreeze doesn't at least do more. I think I heard something about the AEJ being important in that region's climate back when a student? $\endgroup$ – JeopardyTempest Mar 13 at 6:56
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    $\begingroup$ @JeopardyTempest The Ethiopian Highlands acts as a barrier for the moist winds to pass through. The African Easterly Waves are not a feature of the Somali climate. $\endgroup$ – gansub Mar 13 at 12:07

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