Convergence zone lift can at times be somewhat turbulent,  especially if air from different sources is mixing, such as  along a sea-breeze front. The general roughness may be  the only clue of being along some sort of convergence line.  There can also be narrow and rough (but strong) thermals  within the convergence line. Work these areas like any other  difficult thermals, using steeper bank angles and more speed  for maneuverability. Finally, lift sources have been categorized into four types:  thermal, slope, wave, and convergence. Often, more than  one type of lift exists at the same time, such as thermals  with slope lift, thermaling into a wave, convergence zones  enhancing thermals, thermal waves, and wave and slope lift.  In mountainous terrain, it is possible for all four lift types  to exist on a single day. The glider pilot needs to remain  mentally nimble to take advantage of various types and  locations of rising air during the flight.  Nature does not know that it must only produce rising air  based on these four lift categories. Sources of lift that do  not fit one of the four lift types discussed probably exist.  For instance, there have been a few reports of pilots soaring  in travelling waves, the source of which was not known. At  some soaring sites, it is sometimes difficult to classify the  type of lift. This should not be a problem. Simply work the  mystery lift as needed, then ponder its nature after the flight. Combined Sources of Updrafts 10-24