Turbulence Is Trying To Hide From You - Here’s Where to Look
Remember hide-and-go-seek? Well: you’re probably better at it than turbulence.
So why are so many skydivers still caught off-guard?
The answer is probably--predictably--complacency. After all, skydivers aren’t as vigilant about rough air as, say, paragliding pilots. That said: the devil’s invisible rodeo remains a serious hazard for every single person in the air, whether or not their ram-air is meant to get them down instead of up.
Most of the time, you’re gonna be lucky. You’ll meet turbulence under a skydiving canopy high enough above the ground that you’ll just rumble around for a little bit before cruising into smoother air.
Sometimes, though, your luck will run out. When those bumps happen in close proximity to the ground, turbulence tells a very different (and sometimes quite painful) story. Don’t despair--you can use your grownup-level hide-and-go-seek skills to stay in one piece.
Let’s start with the key takeaway: Like the dumbest kid on the playground, turbulence near the ground tends to stick to a few predictable hiding places.
- They’re gonna hide downwind of solid objects. This includes trees, buildings and anything else that’s tall, sticking out of the ground and wider than a flagpole.
- They’re gonna hide above differential ground features.
You can expect different surfaces--such as the lawn of the landing area and the asphalt next to the hangar--to reflect heat differently. You will feel that difference as, y’know, bumps.
Also notable: when the sun heats two dissimilar surfaces to different temperatures, dust devils have the conditions they need to form. These “baby tornadoes” are standbys of desert dropzones, and they can form from uneven heating even when the winds are otherwise calm.
- They’re gonna hide behind spinning props.
Remember shielding your pretty little face from the prop blast as you hopped on the plane? Well, that wind doesn’t go away just because you’re now landing. Keep your parachute (and everything else you care about) well away from the spinning propellers of airplanes chugging away on the ground.
In fact, keep as clear of any propellor as you can, whether it’s spinning or not, always.
- They’re gonna hide behind other parachutes.
Parachutes chum up the air (especially behind them) just as much as any other airfoil would. Don’t be surprised when you’re thrown around when you tuck into an ill-advised CReW move--or chase somebody too closely in your landing pattern.
Not so bad? Okay. Stop smiling so smugly, though: there are a few factors that make the situation way, way worse. If you bumble into the bumps thrown by these suckers, you’re going to have a bad time.
- Stronger wind. If the wind is pretty much zero on the ground, you can generally get away with landing closer to a turbulence-throwing obstacle than you would if the wind were hauling (or even moderate). If you see movement in the wind indicators, do yourself a favor and keep clear.
- Bigger obstacles. The wind will pretty deftly wrap around a narrow tree. A hangar, however, is another story. Tall walls, outbuildings, silos -- they’ll all be bubbling, toiling and troubling on the lee side when the wind is pushing. According to the USPA: “You can expect to feel the effects of turbulence at a distance as far as 10 to 20 times the height of the obstacle that the wind is blowing across.” Do the math: wind blowing across 50-foot-tall trees can cause turbulence 500 to 1,000 feet downwind. Yikes.
One of the first diagrams you’re forced to stare at when you get your initial paragliding license (and every skydiver should, by the way) is one that describes rotor. Since paragliders are basically riding the wind that’s coming off of very, very big obstacles, those rotor diagrams are a good macro view of the turbulence that pours into any wind shadow. As an object gets bigger, those diagrams pretty handily describe the way wind tucks around and churns into the empty space on the other side of it.
Are you ready to play? Thought so. Now count down from 13,500 and find turbulence before it finds you.
Now, dust devils....
How do you spot those, when there is only clean air inside them
Also, just above the receiving side of a hangar, where the air is pushed upwards.....Can make for nice lift, and then that sudden forward surge/drop.
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- When Right is Wrong - by bryanburke (Posted: 2017-11-01)
- It’s Not Your Imagination. Skydiving Actually Changes the Shape of Time - by Annette O'Neil (Posted: 2017-08-16)
- Skydiver's Anonymous - by Andrew Goodfellow (Posted: 2017-07-18)
- Why You're Normally Deviant (And Why You Shouldn't Be) - by Annette O'Neil (Posted: 2017-06-27)
- Learning About Weather: Part 4 - The Small Picture - by Joel Strickland (Posted: 2017-02-27)
- Learning About Weather: Part 3 - Upgrade Your Grey Matter - by Joel Strickland (Posted: 2017-01-10)
- How to Team - Hayabusa's Best Tips - by Annette O'Neil (Posted: 2016-12-13)
- Learning About Weather: Part Two - The Big Picture - by Joel Strickland (Posted: 2016-12-08)