Strong winds, cooler moist air over a hot desert, large high pressure to the east which creates winds in a consistent direction for a distance long enough to set sailplane records, mechanical lift from gradually rising terrain to the north with a southerly wind, streeting at 9 AM with cu's forming before sun rise, early starts for long days, strong lift during the middle hours over the hill country, consistent very good conditions day after day when the normal weather pattern sets up.
Gary Osoba has been studying the weather patterns over southern Texas for a number of years. He has found that the Bermuda high sets up in the Gulf of Mexico and stays there for a couple of months. When it's sitting to the south of the southern tip of Texas, the winds on its west side are from the south straight up the state of Texas. The high is so big, that the circular flowing winds are essentially going in one direction, north, for the length of a hang glider flight (under 500 miles).
These winds circulating around the high are bringing in cooler moister air from the Gulf and pushing it over the hot dry Texas alluvial plane north of the Rio Grande. This cooler air, a few thousand feet thick, is cooler than the desert even at night. Even as the desert radiates its heat back into the clear sky, it is often still hotter than the cool air coming up from the Gulf. Sometimes, in the early morning, clouds will form at 1,000' completely covering the area around Zapata. They will break up around 9 AM, forming streets of cumulus clouds. Streets formed by the winds.
The winds can be strong, 20 mph on the ground and 30 to 40 mph up high. These winds are fed by the strong high pressure over the Gulf. To set world records, you need strong winds to go along with the moderate to strong lift. The winds provide the push, as well as the cool air, which provides the initial lapse rate.
To be able to stay up in the early morning relatively weak lift, before the desert floor is heated up by the sun, you need cu's to see the lift, and streeting to see the lift lines. You need streeting to follow the general direction of your flight so that you can get a fair distance even when the lift is weak.
After the first inversion is broken (when the desert floor has heated up the air below it), and the first lower cu's disappear, you need the second set of cu's to form, and to be set up in streets by the winds. You've got be able to get high enough in the first cu's to be able to stay off the deck while the lift goes from everywhere and weak, to sparse and moderate.
Around noon the cloud base will rise from 2 to 3,000' to 5,000'. The lift will increase in strength and lift sources will be more widely scattered. With streeting you will be able to get under the streets and concentrate on distance and not worry so much about height.
Davis Straub
davis@davisstraub.com
http://ozreport.com