Many different things in skydiving involve the Winds Aloft. In this topic, we’ll talk about how to get a Winds Aloft Forecast, how to interpret them, and what its used for in skydiving.
How do you figure out the Winds Aloft forecast? First, go to www.aviationweather.gov. On the left hand side, read down the column for Forecast. Under it, hover over Winds/Temps >>, then click on Winds/Temps Text. Then a map of codes will appear – these codes are Airport Codes. Just as all major airports such as Chicago O’Hare is ORD, Los Angeles is LAX, etc., ALL airports, including your drop zone dons a unique airport code. For example, Skydive Chicago is 8N2; Skydive Long Island is 3C8, etc. Look at the map closely and choose the airport Code closest to your drop zone, making sure you take note of the Airport Code you choose as we’ll need that for the next part.
Woa!! Talk about the matrix (Illustration 1)!! If you’re not a pilot, this may look like a daunting scroll of numbers! But never fear, we’ll break it down so you can show off your Winds Aloft skills!!
Since a Winds Aloft forecast isn’t determined for every airport in America, you’ll need to figure out either your airport or the nearest airport that reads the forecast (this is why we’ll use the code we clicked on). However, for example, at Skydive Chicago [SDC] we read Joliet’s forecast, which is approximately 30 miles away.
Since I’m based at Skydive Chicago, I’m going to go through the steps above and pull up a forecast. Now scroll to check out Illustration 2:
In the top row, highlighted by green circles, represents the altitudes in increments of 3,000 feet. Highlighted in yellow is the row that represents the airport code that I chose closest to SDC. Now, I just simplified this forecast into 1 row and columns up to 18,000 feet. In skydiving, we generally do not use altitudes above 18,000 feet. Note: The altitudes in the forecast are read in MSL (Mean Sea Level – the altitude above sea level). In skydiving we use AGL (above ground level) as we set our altimeters and AAD’s to ZERO before we jump.
Now let’s read and break down JOT’s Forecast. JOT at 3,000 feet has 4 digits, in this example: 2143 as we see in Illustration 3:
We read these numbers by taking the first two numbers and last two numbers seperately. I like to make a slash mark to make it easier to read as in Illustration 4:
The first two numbers represent the the direction of the wind referencing it from a compass rose. However in aviation, we drop the zero’s at the end. For example, as in illustration 4, the first two numbers are 21. However, it’s read as 210 on the compass rose. Find 210 on the Compass Rose in Illustration 5 :
We can see that 210 is South/South West. Now, the last two digits under 3,000 feet represent the wind speed in knots. So, in our example in Illustration 4, it’s 43 knots. To convert this to miles per hour, multiply Knots by 1.2. In this case, it’s 51.6mph! Wow it’s windy!!!
Let’s go back to Illustration 3 to read the Forecast at 6,000. See if you can interpret it on your own. Note: The last digits behind the + sign is the temperature in Celsius (sometimes it’s – ). Now go through the entire forecast until 18,000 feet. What do you notice in this forecast?
Now why do you think it’s important to know the Winds Aloft? Here are a few things:
* To figure out Jump Run and the Spot
* To figure out how much we’ll be affected by drift in freefall
* To determine how much we’ll be affected by canopy flight between opening altitudes and surface conditions
* To help Wing Suit jumpers determine their flight patterns
Generally, every day will be different. Knowing the Winds Aloft forecast will help you be more aware of the conditions to make better decisions throughout the day and for each jump.
Try this at home: Look up your local forecast and with that knowledge, see if you can determine which way Jump Run will be run before the first load of the day. Or take this information and talk to the pilot about his plan for the day.
Note: If this doesn’t make sense or you’d like more information, talk to your pilot or instructor.
Disclaimer: This is only an article to help determine Winds Aloft and these are only forecasts – meaning they will change throughout the day. You must take responsibility for the conditions of the day.