Weather

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This is a page on how to read the weather, gather resources, and determine the appropriate conditions to fly. For site-specific wind and weather recommendations, see the dedicated page Flying sites.

Ask seasoned pilots

As a beginner, it’s a little intimidating to find out the sweet spot between a mediocre and a dangerous day for flying. Join a social media group (there is an endless amount on WhatsApp / Facebook) and observe. Some pilots are very happy to share their flying forecasts (others less so).

For Cape Town and the surrounding area, consider the Glen Country Club’s paragliding WhatsApp groups (one exclusively for flying-related talk, the other with more banter) by scanning the QR codes on the website with your phone: https://www.glenclub.co.za/paragliding/

Also, please don’t be selfish/lazy and ask something like: “Where can I fly tomorrow?” (then you’re just giving your homework to other people). Rather say: “I looked at the surface winds, the winds at elevation, the temperature, and the rain forecast, and I think that site X might work tomorrow for reasons Y and Z. I’d appreciate it if you can tell me if I’m completely wrong here, missed something, or if anyone has other input.”

Below is how I plan for an upcoming flight, starting about three or four days early.

Surface wind and gusts

You need to safely launch and land, so this is a good place to start.

  • I use Windy and monitor it until the moment of launching (and sometimes during my flight if my flight plan changes). Some of the forecast models (like ECMWF, GFS, IKON, Meteoblu) are more accurate in some places than others.
  • 🇿🇦 RASP (The South African Regional Atmospheric Soaring Prediction) shows the surface wind and often will be more accurate about things like incoming afternoon gusts than Windy. It’s most accurate for the next day’s flying (updated 6 pm, SA time) and on the actual day of flying.
  • 🇿🇦 There are also a good amount of “wind talkers” (also called wind meters), mini remote weather stations around South Africa that report actual current weather conditions, good to compare with the forecast / RASP models.
    • iWeathar (a list of stations, but also a free app for iOS and Android – highly recommended to check wind changes before and during your flight)
    • winds.mobi (a map of more wind talkers, useful to check conditions before and during flights).
    • The Glen Club Wind Talker (a new weather station at the Glen Country Club for Lion’s Head landings)
    • Kommetjie Weather Conditions (not very mobile friendly, but very useful wind meter for flying Cape Town’s “Deep South”)

The wind shouldn’t be too light (especially for a ridge soaring site), but neither should it be too strong for you to safely launch or land, but your instructor / senior pilots will help with this.

Always write down the predicted (and/or actual) wind speed and other weather conditions after flying a site to find your personal sweet spot.

Wind and gusts at elevation

Wind speed, gusts, and direction can be significantly different at different altitudes. Both Windy and RASP (and other sounding forecasts) allow you to see the predicted wind at elevation.

Wind at altitude with Windy

On Windy, select the date and time of your planned flight. Move to the area and select (right-click on web, tap and hold on the mobile app) “Show weather picker” (this will show the wind speed, for the Basic forecast as below; wind lines and speed will show on that point if you select Wind forecast). Then use the slider to see what the wind is going to do at higher elevations: https://community.windy.com/topic/12172/reading-wind-and-gusts-at-different-altitudes.

Wind at altutide with sounding / Skew-T / RASP

(A deeper dive on sounding charts, further down)

The wind barbs on the right-hand side of sounding graphs have all the information you need. The long line (“flagpole” or “vector”) shows you the wind direction, other lines show the wind speed: short lines mean 5 knots (9.3 km/h), longer ones 10 knots (18.5 km/h), triangular ones 50 knots (93 km/h), or a combination thereof.

Note that some sounding charts will indicate altitude in pressure — hPa (hecto Pascal) or millibars– others in feet, others in metres, etc. Just convert these as needed.

Windy.com sounding chart
RASP sounding chart

Precipitation

Paragliders sink, spin, and stall very easily when wet, so rain means no flying, go read or watch some paragliding videos instead.

Some clouds are great for flying, others are very bad, and others are neither good nor bad. Learn to identify them.

I use a combination of Windy (the Basic forecast and Airgram views), RASP, and yr.no to predict cloud cover and the probability of rain.

Sounding / Skew-T

Learn to interpret these diagrams, they’re probably the most important and useful out of the lot. They show you a multitude of information about the sky above you in one image, including:

  • temperature and dew point
  • wind speed and direction
  • instability (good) and inversions (bad)
  • cloud base and more

It will help you immensely in understanding what may make a good or a bad flying day and understand what’s going on in the sky. I won’t try to re-do a lesson here, just watch/read the ones below:

Flight-planning apps

In addition to the weather forecasting apps/sites mentioned, you should subscribe and learn how to use these, especially if you plan on doing XC flying since they show forecasts over a stretch of time and distance:

More thoughts

  1. A good day to fly? Go fly!
  2. Is the wind a little strong? Find a place to practice ground handling (an hour on the ground = ten in the sky). See: Manoeuvres
  3. Is it raining or is the wind too strong to ground handle? Watch videos, read books/articles, listen to podcasts, and study meteorology.

About me

Werner van Rooyen

Formerly Business Development and Marketing at Luno (where we went from eight nerds in a tiny office to hundreds of people spread over three continents) and before that Marketing at PayFast. Currently investing, paragliding, and doing research, mostly in Mexico.