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Weather Forecasting

Accuracy Of Weather Forecasts

Weather forecasters have long been the subject of jokes, probably as much today as they were in Theophrastus's time. One reason for this is that there is no standard measure of a "correct" weather forecast. Suppose that a forecaster predicts heavy rain for your area tomorrow. Does a rainfall of 1 in (2.5 cm) prove that prediction correct? Or a rainfall of 1.5 in (1 cm)? Or a rainfall of 5 in (13 cm)?

Forecast accuracy also is difficult to judge since the average person's expectations probably have increased as the percent skill of forecasts also has increased. A hundred years ago, few people would have expected to have much idea as to what the weather would be like 24 hours in the future. Today, a good next-day forecast often is possible.

In general it is probably safe to say that the shorter the time period and the more limited the geographic area involved, the more accurate a forecast is likely to be. For periods of less than a day, a forecast covering an area of 100 sq mi (259 sq km) is likely to be quite dependable. Predictions about weather patterns six months from now for the state of California are likely to be much less reliable.



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Hodgson, Michael, and Devin Wick. Basic Essentials: Weather Forecasting. 2nd ed. Guilford, CT: Globe Pequot Press, 1999.

Lutgens, Frederick K., and Edward J. Tarbuck. The Atmosphere: An Introduction to Meteorology. 8th ed. New York: Prentice-Hall, 2000.

Lynott, Robert E. How Weather Works and Why. Gadfly Press, 1994.


"Boundary-Layer Meteorology." Boundary-Layer Meteorology 105, no. 3-3 (2002): 515-520.

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The National Weather Service [cited 2003]. <http://www.nws.noaa.gov>.

David E. Newton


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Analogue method of forecasting

—A prediction of future weather conditions based on the assumption that current conditions will produce weather patterns similar to those observed in the past.

Cold front

—The leading edge of an advancing mass of cold air.

Hurricane warning

—A notice issued when a hurricane has been observed either visually or on a radar screen.

Hurricane watch

—A notice to the general public that a hurricane may be expected within a particular area.

Long-term forecast

—A prediction of weather conditions over a matter of weeks, months, or a year.

Mathematical model

—A system of equations that attempts to describe the properties of the atmosphere and changes that may take place within it.

Numerical forecast

—A prediction of future weather patterns obtained by using high speed computers to carry out complex mathematical calculations derived from mathematical models of the atmosphere.

Percent skill

—The likelihood that a weather forecast will be better than a pure chance prediction.

Persistent forecast

—A prediction of weather conditions based on the assumption that the weather over a particular geographic area will remain constant over the near future.

Short-term forecast

—A prediction for weather conditions over a matter of hours or days.

Statistical probability forecast

—A prediction of future weather conditions based on an analysis of the likelihood of various conditions having occurred in the past.

Steady-state forecast, Trend method

—A prediction of weather conditions based on the movement of air masses over a given geographical area at about the same direction and approximately the same speed as they have been moving.

Synopic forecasting

—Scientifically based forecasts derived from the rapid collection and analysis of weather data from as extensive an area as possible.

Additional topics

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