These so-called fronts, named by Norwegian meteorologists after World War I because they resemble a battlefront, normally are part of large weather systems centered on areas of low atmospheric pressure. They are sharp, well defined boundaries between air masses. For the most part, these conflicts and resulting storms do little damage. They move cold air southward and warm air northward, helping to balance the Earth's heat budget. But not all storms caused by the clash of two weather systems are quite so placid.
Thunderstorms cause flash floods, which are weather's biggest killer.
And all thunderstorms produce lightning, the weather's second biggest killer in the United States. Thunderstorms Thunderstorms are convective storms that typically occur during the spring and summer months. The process is similar to the convective processes seen when water boils in a pot. The ascending air cools to its dew point and a cloud begins to form from condensation. As water vapor in the upper portions of the cloud becomes supercooled, raindrops begin to form and fall, dragging down cooler air and producing down-drafts.