Robbie Byrd; age 13, of Scottsboro, Alabama, for his question;

Where do you find a iet stream?

Nobody found one at all until World War II, when our B 29 planes began cruising at 30,000 feet. Nobody even suspected that jet streams existed since no plane had traveled this high before, but the first encounters had everyone baffled. Some of those high flying planes, westbound across the Pacific, had to turn back. The eastbound planes that encountered a jet stream arrived at their destination an hour or more ahead of schedule.

Jet streams are tunnels of turbulent winds, five miles or more above the surface of the globe. However, you could search aloft for a year and never find one. This unusual weather phenomenon is far from dependable. It ranges about 300 miles wide and perhaps four miles deep. It moves along in a wavy pattern which often rises higher or drops lower. Aside from its structure., which is now fairly well known, about the only thing we can be sure of is its direction. The lofty jet stream always whizzes around the globe from east to west.

It seems to be related to the planetary westerlies, for jet streams occur in these wind belts both north and south of the Equator. In spite of their wavy tracks and unexpected movements, they favor certain paths. One general path is frequented aver Canada, another crosses our central states and a third takes a southern route. However, the jet streams that travel these routes rarely stay on course and they tend to vary both in altitude and velocity with the seasons. The ferocity of a jet stream is something never found in the weather near the surface of the earth.

Basically, it is a very swift wind tunnel    with the wildest winds in the center. Near the earth's surface, a hurricane wind starts at 75 miles per hour. Winds at the center of an average jet stream travel around 200 miles per hour, decreasing to perhaps 100 miles per hour at the walls of the tunnel. In a really fierce jet stream, the center winds often reach 300 m.p.h., and have been known to reach 350 miles per hour. In this condition, the gentlest winds at the sides of the tunnel dwindle to only about 200 miles per hour.

Meteorologists are still studying the causes of jet streams, and when these factors are known, perhaps they will have a better idea of where and when to expect them. They  seem to be related to the contrasts of opposing air masses near the earth's surface. From existing charts of their paths, they seem to be triggered by sharp contrasts of temperature between masses of cold and warm air. The fiercest jet streams occur in winter, and seem to be caused by cold air masses moving southward from Alaska and the polar zones. Their paths tend to loop farther south when a polar front pushes farther down in the temperate zones. Hence, some experts suspect that the hag hazard course of a jet stream may be governed by the path of an advancing cold front.

Sometimes a jet stream seems to create stormy conditions much below it near the surface of the earth. Like all winds they are invisible, but sometimes one may trace their activity. Jet streams often tangle with lofty cirrus clouds. Then from the ground, these wispy white clouds look like a long line of foam capped ocean waves.