The warmer air ascends to the top of the atmosphere where it again is re-directed back to its origin.ĭuring 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. 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. It flows along the ground to complete the convection current circuits. Again the air splits and begins to return to 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. The Coriolis effect adds the twist.Īs 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. Prevailing weather is the result of expansive convection currents formed by the temperature differences on the surface of the earth as latitude increases. One air mass can blow in warm dry air today and cold wet air in hours, or tomorrow.

Prevailing weather patterns refer to the movement of entire air masses, not just the winds they produce in their rotations. (This is why hurricanes hit the east coast of the United States.) Eventually, tropical systems can recurve and travel back eastward. This is because tropical cyclones develop over warm sea waters and follow trade winds that blow westward. Often times tropical cyclones (tropical depressions, tropical storms, and hurricanes) travel from east to west. Weather systems can really move in any direction. However, this is not true for all weather systems. 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. is that the Jet Steam moves from West to East across North America. Since low pressure systems spin in a counterclockwise fashion, winds move from the west to the east, propelling weather systems to the east.Īnother MAJOR factor that drives weather systems in the U.S. This is generally due to lower air pressure further north (ex.

In New York, 600 National Guard personnel were on standby.It is important to note that precipitation generally moves from west to east in the Northern Hemisphere.

The forecast prompted the Virginia National Guard to ready 400 troops to deal with emergencies. subway system, took the rare step of suspending operations from late Friday through Sunday. The Washington Metropolitan Area Transit Authority, which includes the second-busiest U.S. All I need now is a wing and a prayer,” said Liz Scherer, 54, of Silver Spring, Maryland. “I have nine cases of wine, half and half and coffee, firewood and all my devices are charged. In addition to snow, the Charlotte, North Carolina, area could get up to a half inch (1.3 cm) of ice, making roads dangerous.įederal offices in the Washington area closed at noon to allow employees to get home ahead of the storm. The storm arrived in the Washington area, home to about 6 million people, after dropping 5 inches (13 cm) of snow in Arkansas and spreading a wintry mess of snow, sleet and freezing rain in parts of Tennessee and Kentucky.ĭuke Energy reported that more than 112,000 people were without power in North and South Carolina on Friday evening.

Weather up and down the east coast