The jet stream is said to play a very significant role in controlling the behaviour of terrestrial atmosphere. Although weather scientists are not yet clear about the ever changing form and features of jet stream, it is true that there is a close relationship between the jet stream and surface weather. But the exact nature of this relationship still remains less understood.
As more and more upper-air data are made available, our knowledge about the nature and behaviour of jet steam is bound to increase. Now, it is an established fact that the so-called polar- front jet streams are closely related to the middle-latitude weather disturbances.
The meanders of the more northerly upper-tropospheric jet stream determine the location of the surface polar front. Besides, the paths followed by the cyclones are also largely controlled by these upper level high velocity westerlies.
Even the distribution of precipitation by extra-tropical cyclones is indirectly influenced by the jet streams aloft. Meteorologists agree that areas lying below the jet may have heavy precipitation.
The jet streams also play an important role in the movement of different air masses which may produce a prolonged period of drought or flood.
Whatever be the cause of the ever changing patterns of the jet, there is hardly any doubt that the jet streams have important repercussions upon the world weather.
There is no denying the fact that a clearer understanding of different aspects of the jet streams will help the weather scientists in making a correct appraisal of the surface weather.
There are evidences that the eddies produced in these upper air streams come down to affect the cyclonic weather. Rainfall, snowfall, thunderstorms of varying intensities, tornadoes, cold waves or snow storms are all directly affected by the jet streams aloft.
Besides, migration of high and low pressure cells on the surface of the earth is also directly related to the shifting positions of the jet streams as they move around the earth.
For instance, the dynamically produced high pressure cells within the subtropical belts owe their existence to the upper westerlies and the jet stream. Thus, it is evident that different surface weather patterns are closely linked with changes in the path of the jet stream.