This a pair of air mass that is neither strong nor weak to replace each other thus waves tend to move along the frontal boundary. A wide variety of fronts are formed in this boundary as usual clouds and precipitation rainfall, here is a lot of water vapor in air masses.
These masses either displayed or become shear lines when density contrasts with the frontal boundaries. Usually as a result of temperature equalizations. where narrow zones of winds shift persist for a time.
Occasionally, cold and warm airflow parallel to the frontal direction and the position may not move any further. The slope of the stationary wave is gentle.
