Weather Forecasting
Because the many variables that affect weather are constantly changing, meteorologists have used high-speed computers to devise atmospheric models that describe the present state of the atmosphere. These are not physical models that paint a picture of a developing storm; they are, rather, mathematical models consisting of dozens of mathematical equations that describe how atmospheric pressure, winds, and moisture will change with time. Actually, the models do not fully represent the real atmosphere but are approximations formulated to retain the most important aspects of the atmosphere’ s behavior.
Computer-generated forecast charts using these models to interpret recorded weather data are known as prognostic charts, or simply progs. At present, there are a variety of models, and hence progs, from which to choose. One model may work best in predicting the position of troughs (elongated areas of low barometric pressure) in the upper atmosphere. Another may forecast the position of surface lows quite well. And some models even forecast the state of the atmosphere 384 hours (16 days) into the future.
A good forecaster knows the idiosyncrasies of each model and carefully scrutinizes all the progs. The forecaster then makes a prediction based on the guidance of the computer. This prediction is a personalized practical interpretation of the weather situation given the local geographic features that influence the weather within the specific forecast area. Since the forecaster has access to hundreds of weather maps each day, why is it that forecasts are sometimes wrong?
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