The jet stream is an amazing phenomenon of weather. From cold winter storms, to warm spring rains, the jet streams bring weather changes to parts of the earth. There are two jet streams in the Northern Hemisphere: The Polar Jet Stream and the less known Southern Jet Stream. There are also two jet streams in the Southern Hemisphere named much the same, except for the fact the pole is on the southern side of the hemisphere.
The Northern Jet Stream is the main jet stream to affect Americans. It was first discovered in World War II when B-29 bombers where unable to reach bombing targets on schedule. When they flew towards their target, their speed was diminished, and when they returned to base, the return trip was quicker due to a heavy tail wind.
But the United States was not the only one interested in the Jet Stream that encircled the earth only 8-12 Kilometer above the ground. Because it moved from west to east, the Japanese used it to send bombing weather balloons to their foes across the ocean.
Since then, weather meteorologists have studied this fantastic continuous wind to find out that though the winds that make up the jet stream continually flows from west to east, the jet stream itself will sometimes dip from north to south. And it never is a “straight” circle around the globe. Instead the jet stream, serpentines across the globe.
When the Polar Jet Stream is north in Canada, warm air fills the United States. However, when it swings south, a harsh cold freeze falls over a large portion of the United States. Most of the time the jet stream stays north during the summer, and migrates south during the winter. This and the position of the sun provide our seasons. The extent of the jet stream will influence the harshness of the winter, or the mildness of the summer.
Because it flows over the ocean, the jet stream picks up warm moisture and can redistribute that heat. The Southern Jet Stream provides more heat and moisture due to the fact it covers more ocean than the Polar Jet Stream.
The jet stream can snake across the atmosphere due to the air pressure that increases when moisture is picked up from the ocean. It tends to move towards a place where it can relieve itself of the pressure of the moisture.
The higher the altitude of the jet stream, the more pressure the moisture exerts on the jet stream. When the warmer, denser, moister air moves though the cold air that makes up the jet streams, it causes wind. The quicker the pressure changes, the more the jet stream snakes to get rid of the pressure, also providing higher wind speeds.
Because the Polar Jet Stream is closer to the North Pole, it is provided with cold air. When the cold air meets up with warm moist air over a land mass, it begins to produce thunderstorms. However, a jet stream can also defuse the storms due to the fact it removes the very tops of the storms. But if the jet stream does this to a strong storm, it will allow the storm to pull more air from the bottom of the storm, almost like a vacuum, and “blow the top off” of the storm.
Because of this fact, jet streams are becoming a more important factor in weather forecasts. However, meteorologists have found it difficult to predict the position of the jet stream that affects our weather. It may remain stationary for days at a time, or quickly move hundreds of miles without warning.
The jet stream is the reason most storms move from west to east. It also is an important factor in the intensity of storms and the seasons themselves. With all this, how the jet streams not have a factor on weather?