by Nayab Naseer

Created on: March 12, 2009   Last Updated: March 27, 2009

THE BASIS OF PREDICTING THE WEATHER

Weather refers to the condition of the air on earth at a given place and time, and the basis of weather prediction depends on two major atmospheric phenomenon. They are:

1. The heat of the sun causes the air to rise and water to evaporate. The rising warm air comes in contacts the cold air in the upper levels of the atmosphere. When this happens, the water vapor cools present in the air and condenses into tiny suspended droplets called clouds. When these droplets become too heavy to remain suspended, they fall to earth as rain, snow, sleet, or hail. A body of air that has similar properties and move together is an air mass. Tracking such air masses provides clues to the future temperature, moisture level, and air pressure of the area into which they are moving. Weather forecasting depends on this fundamental principle.

2. Air pressure is the weight exerted by the atmosphere on the air. High pressure means that the air pressure is greater than the surrounding areas, and Low Pressure means that air pressure is lesser than surrounding areas. This difference in air pressure results in wind, or moving air. Since air is denser in high-pressure areas, air moves or winds flow from the high-pressure area to a low-pressure area. Clouds that cause rain flow with the wind from a high-pressure area to a low-pressure area. Thus, low pressure indicates rains and high pressure indicates clear skies.

Though these two principles are applicable universally, peculiar local conditions, such as the presence of a large water body or mountains nearby might lead to exceptions to the above principles.

FORECAST THROUGH OBSERVATION

Weather forms by the interplay of natural forces. Observing the world around us with a keen eye and a sharp ear can tell us something about these natural forces at play, and thus help in forecasting the weather. In fact, before the invention of meteorological instruments during the last 200 years, much of the world relied solely on these natural signs to forecast the weather. Though technology has proved much of such weather lore as not conclusive, some of them are sound and is still the basis on which people make weather forecasts.

1. Dry air stirs up dust particles and causes the sky to appear red in the west, during sunset. Air becomes dry when there is high pressure. On the contrary, a red sky in the east during morning means that the dry air has already moved past, and that a low-pressure system that carries moisture is approaching.

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