Weather Whys; Polar Front Theory

This is weather wise. Wave cyclones are huge weather systems that can affect the weather for hundreds of miles around them. On a weather map, a wave cyclone appears as the familiar low pressure system with a cold front and a warm front extending front. On a satellite picture, it often resembles a huge comma of clouds. Shortly after World War I, a group of Norwegian meteorologists produced a comprehensive theory to explain wave cyclones. It was called the polar front theory, and it revolutionized the way meteorologists thought about weather. According to that theory, low pressure systems develop along a boundary between two centers of high pressure, one warm and one cold. That boundary is usually represented by a stationary front, with the cold air to the north and the warm air to the south. Now the winds in an area of high pressure spiral out from its center in a clockwise fashion. So the north side of a high has winds moving to the east, and the south side has westward

winds. Since there's a high north of the stationary front and also one south of it, that means the winds just north of the front are blowing toward the west and just south of the front they're heading east. That contrast is called wind shear, and it's what causes a low pressure center to develop. To visualize that concept, imagine you're holding a glass between your palms. Now pull your left palm toward your body and push your right palm away. You'll see that the glass will begin to rotate counterclockwise. Similarly, air caught in the frontal zone will begin to spiral in the same direction, and that movement is an important step toward the formation of a wave cyclone. Weatherwise is produced with the assistance of the Cooperative Institute from Mesoscale Meteorological Studies, the Oklahoma Climateological Survey, and the School of Meteorology, all at the University of Oklahoma. So weatherwise, I'm Drew Barlow.