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Microbursts sound bad, and they are. Here's what you need to know.
While microbursts can form from airmass storms and squall lines, single-cell storms seem to produce most of them.
Microbursts start when heavy precipitation falls from a cloud. As the rain falls, it starts pulling air down with it. At the same time, the air starts evaporating the rain, which cools the air even more. Since the cooler air is more dense than the warm air around it, it descends even faster, forming a microburst.
Dry microbursts are the most common type. With a dry microburst, all of the precipitation evaporates before the column of descending air reaches the ground. This makes them particularly dangerous, because they can be hard to see.
Wet microbursts, as you probably guessed, contain liquid precip when they hit the ground.
When a microburst hits the ground (at up to 6,000 FPM, by the way), it spreads out, creating a vortex ring around the outside of the microburst.
This is where microbursts are really dangerous. If you fly through one, you'll initially have increased performance. But as you enter the microburst, your headwind rapidly switches to a tailwind, causing you to sink. If you're close to the ground, you may not have enough climb performance to fly out of the microburst before you hit the ground. And that would make for a very bad day.
If the outflow speed of a microburst is 30 knots, you'll experience 60 knots of shear as you cross the microburst. And it all can happen in a very short period of time. Think about what would happen to your Cessna 172 if you went from 100 knots to 40 knots in the matter of a few seconds...
How do you avoid a microburst? Don't fly underneath storms, visible virga shafts, or rain shafts. Microbursts don't last long, but they can be extremely dangerous, even while they're dissipating. The best option is always to steer clear and divert around them.
Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at email@example.com.