The Earth's atmosphere exerts pressure based on the weight of the air above. Differences in pressure from place-to-place cause winds to try to flow from high pressure to low pressure regions to even out the differences, but the Earth's rotation and wind friction with the surface act to slow or divert the winds. This animation shows the high altitude wind speeds for the whole globe from September 1, 2004, through September 5, 2004, during the period of Hurricane Frances in the western Atlantic Ocean and Typhoon Songda in the western Pacific Ocean. At high altitudes, the difference between between high pressures from warm tropical air and low pressures from cold polar air try to force air from the tropics toward the poles, but the Earth's rotation diverts this flow to the east, resulting in the high velocity west-to-east jet stream flows at mid-latitudes. The circular flows from Frances and Songda can barely be seen at this altitude.
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