Thunders and Thunderstorms

Thunders and Thunderstorms Thunderstorm is a meteorological phenomenon that contains many hazards to aviation. Many other hazardous meteorological phenomena come together with a thunderstorm: turbulences, strong winds, wind shear, strong upward and downward air currents, icing, electric discharges, intense precipitation (rain, snow or hail), microbursts, gust fronts, funnel clouds and vortexes.
Thunderstorms may consist of a single isolated cloud, cumulonimbus (CB) or a series of cumulonimbus clouds that can be unorganized and organized into a line (squall line) or a cluster (Mesascale Convective Complex – MCC).

The additional issue with the cumulonimbus clouds is their size, since they spread through the troposphere and may penetrate the stratosphere. This means that in the warm part of the year, which is the period of their frequent occurrences, they may rise to some 15 km in height and because of the possible hazards the airplanes may not fly over them but have to fly around.  
Flying under the cumulonimbus may also be dangerous because of the outflow boundary (a boundary separating thunderstorm-cooled air (outflow) from the surrounding air) and the downburst, i.e. downward cold air current.