"phil collin" wrote in message
...
wrote:
I can definately identify with the horizontal turbulence phenomina that
this discusses. But what I'm talking about is not the same. I've
approached this stable at min-sink and identified lift with the
altemeter. Then the vario rises quickly for about 2 second, then the
bottom drops out and I'm in heavy sink


The shear zone near the edges of thermals will create horizontal vorticies.
If you fly through one of these shear vortices at right angles, and the
vortex is rotating the top away from your flight path, you will experience
what you described.

First, you will experience smoothly increasing lift, then as you pass
through the vortex core, a sharp transition to strong sink which will
smoothly decrease. These are commonly encountered when working small,
strong thermal cores since you are spending a lot of time in the shear zone.
A low boyancy/shear ratio can also create them. Just keep circling and
watch your averager.

Bill Daniels