Renita McCarver, age 11, of Tacoma, Wash., for her question:
WHAT IS A WEATHER FRONT?
An important factor in weather prediction is the location of various weather fronts. A weather front is a narrow band of changing weather that can be found between two different air masses. Most weather changes take place along fronts.
When a cold air mass pushes a warmer air mass out of the way, it forms a cold front. When the warm air mass pushes against the cold air mass, it forms a warm front. If the battle goes neither way, it is called a stationary front.
A front formed when a cold front overtakes a warm front is called an "occluded" front.
Weathermen usually predict overcast skies and continuing rain or snow ahead of a warm front. Showers or squalls usually form along a cold front.
Almost all weather changes in North America occur along the polar front. In this region, the cold, dry polar air mass battles with the warm, moist air mass from the high pressure belt of the subtropics. Many storms come about as a result of these differences in temperature and humidity between air masses.
An air mass is a large body of air that has about the same weather conditions throughout it. Air masses may be warm or cold, dry or humid.
Wind is the movement of masses of air. Winds are named by the direction from which they blow. A south wind, for example, blows from the south to the north.
Since May 1955, computers have been used to help some of the weather forecasts. They are used to predict certain basic elements of future weather since they can analyze weather maps and use all available scientific weather knowledge.
High, or anticyclone, is a large area of high pressure. In the Northern Hemisphere, winds blow clockwise in a high.
Low, or cyclone, is a large area of low pressure. In the Northern Hemisphere, winds in a low rotate counterclockwise.
Pressure is the force produced by the weight of air pressing down on the earth.
Weather forecasts are made with information that is obtained from weather stations throughout the world. Forecasters analyze the information and base their predictions on the patterns that come in from all locations.
Unfortunately, weather systems do not always act the same way and often weather predictions are wrong. But in the majority of cases, the scientists who make the predictions are usually fairly accurate.