Casting Tips
Under the Wind
You know the issue. The wind is blowing like stink and you're told that a side-arm cast will get your fly line out of the wind. The premise is that the wind speed decreases closer to the ground. Although the premise makes sense, the advice always left me a little flat. I was reviewing some old articles from The Loop, the Federation of Fly Fishers Journal for Certified Casting Instructors, and came across one from 2001 by Larry Pratt. Larry apparently had a colleague who worked at Woods Hole Oceangraphic Institute and they actually took a scientific approach to the problem.
Take a look at this graphic produced with data from Dr. Jim Edson, Larry's colleague. 
The figure shows a typical example of a mean wind profile over the Pacific Ocean along with a six-foot fly caster holding a nine-foot rod. The data was collected on a moderately windy day.
The average wind speed at the top of the caster's head is about 20 mph and at the level of the fly it is about 22 mph. So let's look at the impact of the standard "cast under the wind" advice. A side-arm cast will get the fly and fly line down to about 4 feet off the ground. The wind speed here is about 18 mph, representing a decrease of less than 20%. Most of the decrease in wind speed happens in a very thin layer right next to the ground.
So, work on other techniques to handle the wind like nice tight controlled loops and line speed rather than trying to cast horizontally below three or four feet.
Based on Under the Wind by Larry Pitt, The Loop, Spring 2001, Federation of Fly Fishers, with permission. Graphic by Jack Cook, Larry Pratt, and Jim Edson. For the complete article go to The Loop Index.