Cumulonimbus or Cb, is one of the vertical clouds that can grow up to a height of 60,000 feet (18 km), and is formed due to several causes, the most common being the convection process due to warming of the earth by solar radiation and unstable atmospheric conditions. Cumulonimbus is very easy to form in the tropics because the convection process in this region is very strong, and from this cloud are born various phenomenon of extreme weather such as tropical storm (typhoon), lightning storm (lightning rain), hail (ice storm), tornado Until the wind nipple Pickaxe that some time ago in Bandung.
Cumulonimbus clouds are easily recognizable from their distinct appearance from the others, with a sloping cloud base, a towering cloud 'mast' and a base-shaped peak or base to forge metal.
This cloud is very dangerous for the flight due to several things. The first is the vertical draft process or the vertical movement of the air that occurs in the cloud. This vertical movement can rise (updraft) or downdraft, and this process is actually common in the cloud. Bumping that occurs when the plane we are traveling into the cloud is also caused by the vertical draft. In Cumulonimbus clouds, this process is much stronger, and the resulting turbulence can throw the plane trapped inside. Another dangerous factor is the Cumulonimbus cloud ice particles that can freeze aircraft parts, including engines. And because these ice particles too, Cumulonimbus clouds are one of the most frequent types of clouds that can disrupt electrical systems and aircraft navigation.
Since the Cumulonimbus cloud tops can reach 60 thousand feet, pilots will generally choose to avoid these clouds to the side (jets generally fly at 30-40 thousand feet, or about 9-12 miles).
Another type of cloud that is harmful to aviation (especially in Indonesia) is the Lenticular cloud, so named because of its shape similar to the lens. In contrast to Cb, the Lenticular cloud is formed due to airflow passing through obstructions, such as mountains, which causes eddies that form these clouds. The Lenticular cloud is easily recognizable from its UFO-like shape,
Lenticular clouds can cause strong turbulence for aircraft that fly close to the peak of the mountain and unique, this cloud is generally favored by lovers of Glider because of its strong lift.
In addition to clouds, there are also some atmospheric phenomena that are generally not visible, but very dangerous for aviation, such as Virga. Virga is precipitation or rain that does not reach the surface because it evaporates in the atmosphere.
As the water / ice particles that fall from the clouds evaporate, the heat absorbed by the process will cause the surrounding air temperature to drop dramatically and heavier, resulting in a very strong downdraft (microburst), potentially producing extreme turbulence on the airplane passing underneath . Although usually rarely observed from below (the surface of the earth), Virga can be seen on the flight, with a curtain-like shape dangling from the clouds