Why does weather move from the west to the east?
During a day the West takes a lot of sunshine (hot air) but the east cools down (since it is under darkness)
When sunlight hits (around 2 p.m.) hard, air becomes hotter and this air moves upward. On the eastern side, though, air becomes cooler since around midnight sunshine has ended nearly 4, 5, or 6 hours ago. Therefore, on the eastern side weather is cool.
The air moves from hot to cool. That is why air moves eastward.
Low pressure spins counterclockwise, causing weather systems to move from west to east in the Northern Hemisphere.
It is important to note that precipitation generally moves from west to east in the Northern Hemisphere. This is generally due to lower air pressure further north (ex. North America) than in the tropics. Since low pressure systems spin in a counterclockwise fashion, winds move from the west to the east, propelling weather systems to the east.
Another MAJOR factor that drives weather systems in the U.S. is that the Jet Steam moves from West to East across North America. This is largely due to a variety of factors including the sun's heat primarily targeting the equator, the speed of the Earth's spin and more.
However, this is not true for all weather systems. Weather systems can really move in any direction. Often times tropical cyclones (tropical depressions, tropical storms, and hurricanes) travel from east to west. This is because tropical cyclones develop over warm sea waters and follow trade winds that blow westward. (This is why hurricanes hit the east coast of the United States.) Eventually, tropical systems can recurve and travel back eastward.
Note that weather movement from west to east occurs only in certain regions of the globe. It depends on where you are.
Prevailing weather patterns refer to the movement of entire air masses, not just the winds they produce in their rotations. One air mass can blow in warm dry air today and cold wet air in hours, or tomorrow.
Prevailing weather is the result of expansive convection currents formed by the temperature differences on the surface of the earth as latitude increases. The Coriolis effect adds the twist.
As air heats up due to the direct rays of the sun and higher temperature at the equator, it rises and moves up into the atmosphere where it cools again and begins to flow high aloft, at the same time turning north or south depending on its origin.
In both hemispheres the convection current meets a similar convection current generated in the temperate latitudes of earth, and both force each other back down towards the ground. Again the air splits and begins to return to its origin. It flows along the ground to complete the convection current circuits.
Near the earth's poles, the same event is also in progress, except the colder air produced there stays near the ground on its journey south or north, then rises as it is heated, where it meets the other side of the temperate air described above. The warmer air ascends to the top of the atmosphere where it again is re-directed back to its origin.
During all this activity spin of the earth results in the Coriolis effect which deflects the winds towards the right in the northern hemisphere and to the left in the south. Depending on which hemisphere and the latitude of a particular location, the effects of these two phenomenon will determine the prevailing weather.
Pictures of the earth's convection currents are here.
The Coriolis effect is described here: