Trough (Meteorology) trough troughs trough lines trough short wave trough trough inverted trough Trough (Meteorology) troughs trough trough inverted troughs upper level trough Trough (meteorology) trough troughs upper-level trough trough inverted trough Trough trough of low pressure trough trough troughs English English trough troughs inverted English trough trough trough upper level trough trough troughs Trough (Meteorology) upper level trough English inverted English frontal trough upper level trough trough low pressure trough trough trough