Warm air moving into an area of cold air is called a warm front . When a cold front overtakes a warm front and forces the warm air aloft, it is called an occluded front . An important weather system affecting middle and high latitudes is a traveling low pressure system called a wave cyclone . Wave cyclones move from west to east and involve interaction of warm and cold fronts that often produces cyclonic precipitation. A tornado is an intense low pressure system with very high wind speeds.
Tornadoes develop with thunderstorms and hurricanes.
A weather system associated with tropical areas is the easterly wave , a low pressure trough into which air converges and is lifted producing precipitation. A polar outbreak occurs when cold polar air forces its way into very low latitudes, bringing storms followed by cold, clear weather. Tropical cyclones often create tremendous damage due to high winds, high waves, flooding and heavy rains. The atmospheric circulation transfers heat from equatorial regions toward the polar regions by the Hadley cell circulation, air mass movement, Rossby waves and tropical cyclones. List six kinds of typical air masses and their source regions.