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Before you fly around thunderstorms this summer...
If you see a thunderstorm with numerous lightning strikes, the updrafts and downdrafts inside it are likely to be extreme. Air moving up and down at thousands of feet-per-minute causes friction, resulting in lightning strikes.
At a minimum, stay 5 miles from smaller cells. The FAA recommends you fly 20 miles or more away from large, severe storms. Hail and severe turbulence can be found several miles away from visible storm cells.
If you find yourself in convective weather with turbulence, focus on keeping the wings level. Slow below Va and accept large altitude and airspeed deviations. Slow to Va, or your manufacturer's recommended turbulence airspeed.
With flat cloud bases in-sight, compared to thousands of feet of towering cumulus, you might be tempted to fly beneath a thunderstorm. If you get caught under a thunderstorm as it reaches the dissipating stage, you could encounter severe downdrafts exceeding 6,000 FPM. As rain becomes heavy, more air is pulled down with it. At this point, the thunderstorm will begin to die quickly, but it's also the most dangerous time to be caught underneath it.
With the right conditions, it only takes a few minutes for a seemingly benign cloud to become a full-blown thunderstorm. So what's the best advice to stay safe? If the cloud looks like something you wouldn't want to fly through, you shouldn't fly under it either.
When the temperature in the atmosphere decreases faster than 3 degrees Celsius per thousand feet, the atmosphere's absolutely unstable. This means that any time you lift up air from the surface, it will be warmer than the air around it, and it will continue to rise.
What could cause the air to rise? On a hot summer day, surface heating from the sun. Thermals, the light to moderate turbulence you feel when flying on a summer afternoon, are a perfect way for the air to rise quickly.
As you lift air from the surface, it cools. The temperature keeps dropping and approaching the air's dew point. Once it hits the dew point, moisture starts to condense out of the air, forming clouds. This altitude is the convective condensation level. It's the lowest altitude where condensation occurs because of convection from surface heating.
As moisture condenses out of the air, it releases energy. (It takes energy to turn water into a gas, and that energy releases as heat as the gas condenses back into water.) Now your parcel of air is actually cooling less than 3 degrees Celsius per thousand feet, because moist air cools more slowly than dry air.
Now that moisture is condensing out of the lifted air, it's much warmer than the surrounding air. As it rises, that temperature gap grows, and the air continues to accelerate upward, forming a strong updraft. This creates a towering cumulus cloud, or TCU. And with that, you have the developing stage of a thunderstorm.
Have you had a bad weather encounter around thunderstorms? Tell us about your experience in the comments below.
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