In Nevada and Utah (my usual flying territory) summer brings afternoon “monsoon” thunderstorms.
Use your PilotGEEK flight briefer to avoid thunderstorms
These pose a huge danger to small aircraft, and I’ve had unpleasant experiences even thirty miles away from them.
When I was on the “long cross country” required for my private pilot rating, I was flying from Salt Lake City to Wendover, Nevada. A very long, easy, no problem flight. There were indications of thunderstorms far to the west of Wendover, but I was sure that I could get there and back again without a problem.
On the way back, however, I received a text alert of a weather change at the Wendover airport from the PilotGEEK on my cell phone, and noticed a dreaded green blotch behind me on the weather radar on the G1000. It was more than 30 miles away, but I noticed mild to moderate turbulence. At one point, my Skyhawk suddenly dropped about 50 feet! My headset came off my head and bounced off the ceiling, and my glasses fell off.
Thankfully, that was about it for the storm. I put the throttle to the firewall and kept the storm as far behind me as possible. (It never got closer.) And I booked it back to Salt Lake City, and was VERY thankful when the wheels squeaked on runway 17 at KSLC.
I love flying in the morning, especially in summer. I always check the weather, and even then try not to plan afternoon flights (between about 1 and 4 P.M.) The weather in your area probably has a different pattern, but the key point is to learn the patterns and check the weather.
A quick refresher:
A thunderstorm is said to have a “life cycle” of three, progressive stages:
- Cumulus Stage
- Mature Stage
- Dissipating Stage
The Cumulus Stage
Not all cumulus clouds become thunderstorms, but every thunderstorm begins as a cumulus cloud. The cumulus stage is characterized by the uplifting of the moist, unstable air . This updraft extends from near the surface to the top of the cloud and varies in strength. Clouds may grow at the phenomenal rate of 3,000 feet per minute, which means they can easily outclimb your aircraft. The time-honored rule of thumb is never to climb to avoid a thunderstorm because you can be overtaken by the updraft.
The size of water droplets is very small in the early part of the cumulus stage, but the size of the droplets grows with the size of the cloud, and they quickly become raindrop size. When the rising air carries the water droplets above the freezing level, the potential for icing conditions is created. Eventually, the cold raindrops grow so heavy they cannot be sustained aloft by the uplifting air, and they fall, dragging air down with them. When the downdraft coexists with the updrafts, the thunderstorm is said to be mature.
The Mature Stage
When the rain begins to fall, it signals the creation of a downdraft and the maturity of the storm. The cold rain now lessens the latent heat created by condensation, making the downdraft cooler than the air surrounding it. Pilots on the ground shiver and jokingly comment on the “air from 50,000 feet” when they feel that first rush of cool air before the rain arrives. Because the air in the downdraft is cooler than the air surrounding it, it accelerates downward-up to 2,500 feet per minute-then spreads outward at the surface. This is characterized by strong and gusty surface winds, a temperature drop that is sometimes sharp, and a quick rise in pressure (cold air is more dense). This surface wind surge is sometimes referred to as a “plow wind” or gust front because it pushes air (and other things) in front of it aside.
Even with all this down-rushing air, updrafts in the mature stage have reached their maximum-possibly now 6,000 feet per minute. When you have updrafts and downdrafts so close to each other, they create strong, vertical shears and extreme turbulence. The mature stage is the time of the thunderstorm’s greatest intensity. Yet, the downdrafts are also the beginning of the end.
The Dissipating Stage
The rain ends, downdrafts cease, and the thunderstorm is over. The cloud forms its characteristic anvil, pointing to where the air mass is headed. The clouds remaining are harmless now, unless they take in more moisture, become unstable again, and encounter another lifting force. The life cycle starts again.
Have fun, and fly safe this summer!
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