Weather Hazards

Severe Thunderstorms

There is no shortage of weather phenomenon that affect the ability to safely operate an aircraft.  In fact, many of the systems employed in the airframe are specifically designed and built to allow for operation in adverse and extreme weather conditions.  Anti-icing systems, heating, cooling, radar, rain removal, navigational aids, and landing systems are all designed to help the aircraft and crew negotiate the different elements of weather.

Regardless of the amount of thoughtful design and flight planning, there are some weather events that should be avoided completely.  This is the reason that Severe Thunderstorms rank as the greatest weather risk to aviation operations.

There are three main factors that must be available for a thunderstorm to form:

Moisture – Thunderstorms are more likely when the surface dew point is greater than 55 degrees Fahrenheit.

Lifting – Something must be the initial push that causes air to rise.  This could be a frontal boundary, a low-pressure system, or low-level differential heating caused by the sun.

Instability – Is caused when air rises vertically.  This can happen when a less dense air parcel moves upward through air that is more dense.

The picture above shows a cold front advancing, which starts the lifting of warm and moist air over the top of the cold air mass plowing underneath.  This creates instability as the warm air rises vertically and condenses.

Thunderstorms can come in all shapes and sizes.  A single-cell thunderstorm or a small squall line might not be that concerning, but a supercell thunderstorm (pictured above) that is ten miles in diameter, reaches 50,000 feet AGL, and lasts for over an hour, is something that grabs a pilot’s attention.  During flight planning, pilots and aircrew should find a method to circumvent this severe weather or stay on the ground.

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References:

Federal Aviation Administration (FAA). (2016). Pilot’s Handbook of Aeronautical Knowledge (PHAK). https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/

Haby, J. (n.d.). Thunderstorm Ingredients. Weather.gov. https://www.weather.gov/source/zhu/ZHU_Training_Page/thunderstorm_stuff/Thunderstorms/thunderstorms.htm#top

Midwestern Regional Climate Center. (n.d.). Living with weather: Thunderstorms. https://mrcc.purdue.edu/living_wx/thunderstorms/index.html