Imagine strong thermals rising through a strong wind. We have two types of current colliding at right angles, so there will be significant turbulence and thermals may not have consistent texture or shape. When wind distorts them a subtle variation of the uniform circle may help to maintain position within their cores. Flying a broad, flat turn on the windward side of each circle and a tight, steep turn on the lee side can offset that tendency to drift downwind from the best lift. This is essentially the same maneuver that power pilots refer to as ‘turns around a point’.
Even in the center of a large thermal, if you lose contact with the strongest lift you probably have been ejected by the turbulence of the core. (Or rather the air you’re rising in has been ejected.) When this happens it usually will push you out the downwind side as your thermal boils up through stronger horizontal winds at higher altitude. New lift rising from the same source will arrive upwind of the position to which you have drifted. So again, in the absence of any other indication and especially if a climb seems to have slowed with unexpected suddenness, moving upwind will often bring a climb back to life.