This SEL pilot always steers clear as I'm concerned about the 'ups' and 'downs' therein.
So, how do you determine where the 'up' and 'down' areas are based on the cloud orientation??Interesting home page, btw...
The up is in "front" of the cloud. Front end being defined by the upper level wind direction. If the upper level winds are blowing west to east the front of the lennie will be on the west side of the cloud. I took one to 25,000 feet at Black Forest, Colorado. It is a hell of ride. When you go through the rotor it is violently turbulent but once through the rotor you are in laminar flow air. Your rate of climb indicator can be greater than 1000 feet per minute and the air is totally smooth. It does not get any better than that.
Primarily the wind direction and the lay of the land. Here in SE Tennessee we get wave in a variety of directions off the Cumberland Plateau. The highest altitude gains, and the current TN state altitude gain record of 17,400', are in the NW wave, although it's also the most turbulent to get to and it's usually blowing stink on the ground when it sets up. The South wave is much more docile, with almost no ground wind, but not nearly as high as the NW wave. What you have to avoid is the areas between the waves, most notably between the downwind side of the primary wave and the upwind side of the secondary wave. If you know the wind direction it's not hard to predict where the up's and down's will be.