Evaluating Wind and Turbulence
by Tom Buchanan, S&TA

Turbulence and wind gusts are always threatening to a parachute pilot, but often that disturbed air is difficult to see, and even more difficult to quantify.  Thus, the decision to jump or to stay on the ground can be a tough one, especially for low-time skydivers.  So with that in mind, lets review a few ways to evaluate conditions.

First and most obviously, we can look the wind sock, or more correctly, we can look at all the wind socks and small streamers on the DZ.  The various wind indicators will tell us not only how strong the wind is, but also what direction it is coming from.   Wind moving straight down the runway is generally not so awful, but wind crossing over trees can be far more problematic and should be cause for caution.  Likewise, if all the wind direction indicators show a consistent wind in one direction, the air will be pretty stable.  Of course if each wind sock shows wind moving in a different direction we should be looking out for trouble, especially if the wind is strong.

If the forecasted winds aloft at 3,000 feet are strong we can expect surface winds to be strong too, and frequently turbulent.  Often when upper level winds are strong and surface winds are light we will see the stronger winds work their way down through the day.  Wind speeds and turbulence generally increase through the day, then ease up as sunset approaches, so moderate surface winds early in the morning can be expected to change, and may intensify as the days wears on.  That doesn't always happen, but if the day is young and winds at 3,000 feet are strong, caution is advised.

If the forecast calls for a front to pass we should be expecting a change in wind direction and intensity, and that can create ugly turbulence.

When we are on the ground we should be looking at other parachutes land and watching how they react to the wind.  As we watch canopy traffic we need to take into account who is flying, and what kind of parachute they have.  More experienced jumpers will generally be flying smaller and faster canopies that will respond to wind in a different way than larger parachutes in the hands of beginners.  Tandems too behave differently.  So, while watching parachutes land, try to keep your eyes on people of your experience level flying parachutes like yours.  Not only will you get an idea of how the parachutes are reacting to the wind, but you'll also have a chance to closely evaluate how somebody else deals with the wind.  Keep in mind that parachutes like to flex a bit while flying, so every little ripple shouldn't be cause for concern.  In fact, often an experienced jumper will be flying a high performance canopy and barely even notice an obvious ripple.  However, any loss of directional control or a tendency to collapse is cause for serious concern.

As you watch canopies bounce around, try to figure out why.  We all know that turbulence tends to concentrate behind the treeline, and on a hot day we can often expect updrafts over the runway as warmed air raises, and downdrafts next to the runway as colder air swoops in.  Keep track of those "danger zones" and avoid them when planning your flight path.

While watching landings try to stand next to an experienced jumper who you trust.   Ask what he is thinking about the wind, and why.  Use every landing session as a chance to gain experience and knowledge from the "old timers."  Old people like to talk.  Really.

Once everybody is on the ground it's pretty easy to ask the folks who just landed how the conditions were.  Just as when we are watching landings, we should evaluate answers based on the parachute type and experience of the flyer.  It's a great idea to let an experienced jumper or instructor know what your specific experience and comfort levels are, then ask what they think of conditions in that context.

It's also a good idea to look at who is jumping, and who is on the ground.  If the hot teams and freestyle jumpers are remaining on the ground chances are conditions are pretty bad, even if the less experienced people are still jumping.  Tandem instructors often jump their large canopies under stronger winds than solo jumpers, so they should not be used as a very reliable guide.

The Ranch has a wind meter positioned on a pole between the school and the hanger.   Everybody is welcome to have a look at the readings, but keep in mind the sensor is not well positioned and readings are sometimes suspect.  Still, if you check the wind indicator often enough you will develop a sense of when it is accurate, and when the readings should be deeply discounted.  The school may also have a handheld wind meter available to borrow and use in the open field, or these devices may be purchased for a few dollars from parachute equipment dealers.

An accurate and objective real-time measure of area winds is available by telephone from local airport reporting points.  These phone reports are provided by a computer synthesized voice based on conditions "right now," or by an observer who files a recorded loop.  The automated systems take readings every five seconds and update every minute.  Wind speed is reported in knots, and reports of gusts are based on average and peek readings over the previous 2 minutes, 10 minutes, and 60 minutes, and are compiled by an algorithm that provides a longer time-average when the wind is strong.   The reports also include ceilings and visibility, as well as other information pilots often need.  The reporting points are not right at The Ranch, but I've found that if several area airports are reporting strong gusts, then we should consider that we are experiencing similar conditions at our field.  If you have a cell phone, make a call before you make a decision.  Here are the area phone numbers that will provide weather detail:

The same information provided by phone is compiled and sent to the government weather service and is available via laptop computer at commercial sites including: http://www.wunderground.com/US/NY/Gardiner.html .   The local reporting stations only update the host computer every 15 minutes, but the synthesized phone message is updated every minute.

It would be super easy to make a go-no-go decision based on just one of the above parameters, but life isn't that simple.  As you make your own decision try to balance all the weather sources.  Keep in mind that you should be trying to learn and grow in small steps.  Conditions that you reject today may be fine in another 100 jumps, but only if you keep pushing yourself... slowly.  And try to remember the "10 minute rule"... if you need to spend more than 10 minutes thinking about your decision, then conditions are probably beyond your ability.

Learn and grow.  Share your new knowledge.  Have fun.  Stay safe.