Weather Phenomena in Tenerife 6 is the last article in a series of six that cover specific weather phenomena in Tenerife and, by extension, the Canary Islands. In this article is about trade wind.
After five articles about the weather that have appeared in this series under the name “weather phenomena,” there is still one meteorological phenomenon that we have yet to address. The trade winds (passat) are a very consistent easterly wind that blows year-round between the subtropical high-pressure areas and the Intertropical Convergence Zone. This is the final installment for now: Weather Phenomena in Tenerife 6 – Trade Winds.
On the island, people refer to una panza de burro or a donkey’s belly. These are clouds that form daily above the northern edge of the island and are especially common in the summer. Note that summer here lasts until the end of the year. The reason these clouds are called a donkey’s belly has to do with how they look from below, resembling a compact mass of clouds in color and appearance.
Condensation Clouds
It’s like the theory of relativity, where the perception of space and time depends on the laws of physics and not on the speed of the observer relative to other observers. Something happens to the summer clouds north of the most mountainous islands in the Canary Archipelago. Meteorologists are not surprised that stratocumulus clouds accumulate in these locations.
For clarity: this weather phenomenon only occurs in the north of the island, where the mountains rise steeply from the coast.
Sun versus Rain
The meteorological conditions on an island are different and so distinct from those on a continental landmass. The past summer was a reminder of this on the north coast. Every day brought clouds—low clouds that sometimes produced drizzle or even heavy raindrops. Mother Nature is pleased with this, as are farmers. But tourists are not. They come for the sun, which is mostly guaranteed in the south. Hence the concentration of sun-seekers in the southern parts of the island.
But sometimes, clouds also appear in the south. More on that later.
Rubén del Campo
How should I describe this cloud formation with a clear explanation? The language of meteorologists is difficult to translate, and when we manage to do so, it might sound childishly cynical. In any case, I’ll give it a try, but not before quoting Rubén del Campo, a renowned meteorologist from the Centro de Investigación Atmosférica in Izaña and the Agencia Estatal de Meteorología (Aemet). He said, “If there were no islands in the Atlantic Ocean, clouds would not form off the west coast of Africa.”
Vientos Alisios
As with everything, there is a cause and a reason. The driving force lies in the Azores high-pressure system. Around this persistent high-pressure area, the wind moves clockwise along the isobars—the lines that connect points of equal pressure and appear, to the layperson, as a spider web on a weather map.
Together with this motor, a thermal low-pressure system forms over the African continent during summer due to the intense heat over the Western Sahara. This is responsible for setting the trade winds in motion. The presence of this low-pressure system causes the trade winds to travel greater distances in the summer, picking up more ocean moisture as they go.
This cooling vientos alisios, laden with moisture, is forced to rise when it reaches the islands. Due to the island’s mountainous structure, this maritime air is pushed upward. And we all know from physics class that rising air cools, causing the moisture it contains to condense.
Warm Air Cap
The donkey’s belly then turns into a sea of clouds, or as a Canario so beautifully puts it, Mar de nubes. If you look north from higher elevations, you won’t see clouds up high, but rather a sea of clouds above the island’s edge. It’s beautiful and spectacular. Strangely, these clouds do not rise higher than 800 to 1,000 meters. At this altitude, they encounter a thermal layer that acts like a lid on a pot. This is due to subsiding air masses from high pressure, which warm and dry as they descend closer to the Earth’s surface. This warm cap is what creates the typical cloud cover with a pronounced horizontal spread.
Rising Clouds
If clouds, driven by the active generators, manage to rise higher than normal, then we have a problem on the leeward side of the large mountain. The northeast wind pushes the clouds southward. A broad band of stratus clouds sweeps southwest, spoiling the sun for the sunbathers. You can solve this by moving a few kilometers to get away from the cloud band. But I hope the wind doesn’t change direction.
Also check out the previously published articles about weather and climate on Tenerife:
Part 1: Phenomena
Part 2: Calima
Part 3: Winds
Part 4: Clouds
Part 5: Waves
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