rodbailey

Basic Weather
by Dixon White ( http://eagleparagliding.com )

This is the first in a series of columns that will review step by step concepts concerning weather and flying pointers. Get together with your local instructor and club to discuss these topics in greater detail. Be sure and expand your library of books and videos. This column will recommend certain books and videos, realize that there may be some ideas that are arguable. Practice the weather concepts daily, even when you aren't going flying. Begin to identify the trends that make for the best coastal flying, thermal conditions or exhaust heat sessions. Give your chums a call who flew on days you couldn't and see how close you can get to predicting the conditions. Be thoughtful about going to new areas and how powerful some atmospheric influences may be in contrast to your home sites. There are some sites that become unruly by 9am in August yet others that can be flown all day.

There are a couple of clues in the macro view of the atmosphere that can help you visualize approaching weather as much as 3 days in advance. Planning ahead for the possibility of flying can sure make the "home" scene and relationship with the "boss" much easier. You may rather be at home getting through a list of "honey-do's" instead of driving for 4 hours without any flying.

Through the Internet, television weather reports, and the National Weather Service you can find Jet Stream maps for as much as 5 days away. For example, you can select www.weatherchannel.com (www.paraglide.com has a very thorough weather section also) go to maps and find the Jet Stream forecast for the next 5 days. In general, it seems accurate for only 2 to 3 days out. If the Jet Stream is moving into your area, within 100 miles, there's a pretty good chance that flying will be switchy (changing direction dramatically within seconds), demanding (gust differentials beyond the optimal) or impossible (just too darn strong). Although the Jet Stream is many thousands of feet over the ground it draws cold fronts, which can then drop the pressure and lower upper level temperatures thus reducing stability. The Jet Stream can have an influence on surface winds as strong upper level winds can mix to the ground once the inversion has melted. You may notice on some days influenced by the Jet Stream that surface weather conditions can change within a few minutes. You may also notice fast accumulating cirrus cloud cover with 2nd and 3rd layers of clouds appearing very fast, indicating degenerating stability. Keep in mind that flying sites at sea level, or near sea level, will be influenced less than high mountain sites. If you are going to fly in questionable conditions make sure your glider is user friendly as well as the site - avoid high performing gliders and sites in rough terrain. Keep an eye on the cloud development and landing field winds - land before conditions can make your touchdown eventful.