Thunderstorms have a nasty habit of showing up when you don’t want them to. They can be especially dangerous to aircraft and pose a threat to safety of flight. It is important that pilots understand how a thunderstorm works and know the adverse conditions that are associated with a thunderstorm to avoid an accident.
How a thunderstorm forms
In order for a thunderstorm to develop, there must be sufficient moisture in the air to create clouds, there must also be a lifting mechanism, usually caused by uneven heating of the earth’s surface. Clouds will start to build and warm air will rise in the atmosphere lifting the clouds and moisture high into the earth’s atmosphere. This is known as the Towering Cumulus Stage.
The next stage, the “mature” stage, is classified with precipitation, turbulent air, sometimes severe, and lightening strikes in the clouds as well as cloud to ground.
The final stage is known as the dissipating stage, during this final stage, the updraft has
ceased and the storm is dominated by downdrafts. Precipitation
may still occur, but will decrease with time as moisture is depleted.
Hazards associated with thunderstorms
Wind Shear: Thunderstorm outflow can cause extreme changes in
wind speed and direction near the surface during critical phases of flight. Microbursts are possible
with many thunderstorms, as is heavy rain. Often virga and blowing dust on the surface are your
only clues to the presence of a microburst.
Icing: Because thunderstorms are driven, in part, from the conversion of liquid water to ice,
pilots can expect to find airframe icing in all thunderstorms. Although
all forms of icing are possible, clear icing, caused by larger drops of
supercooled water, is the most common. Ice accumulation can be
rapid. Supercooled water and clear icing can extend to great heights
and to temperatures as low as -20 degrees C. Icing will impede airflow over the wings and cause immense drag as well as airflow separation over the wings, icing has been a factor in many aircraft accidents over the past century.
Lightening: lightening strikes are dangerous enough, they burn hotter than the surface of the sun, and can damage aircraft if a bolt should strike.
The most important thing for a pilot to understand is the environment around them, there are many tools at their disposal, such as computers to track the weather patterns and know when and where a thunderstorm is likely to occur. It is best to avoid thunderstorms by at least 20 miles on either side and always be situationally aware of the weather for your route.