Weather Forecasting

A daily weather forecast involves the work of thousands of observers and meteorologists all over the world, and the work of thousands of machines. Modern computers make forecasts more accurate than ever, and weather satellites orbiting the earth take photographs of clouds from space. Forecasters use the observations from ground and space, along with formulas and rules based on experience of what has happened in the past, and then make their forecast.

Types of Forecasting

Meteorologists actually use a combination of several different methods to come up with their daily weather forecasts. Here are the different types:

1. Persistence Forecasting: This assumes that what the weather is doing now is what it will continue to do. To find out what the weather is doing, meteorologists make weather observations.

A thermometer measures temperature.
A barometer measures air pressure.
A rain gauge measures precipitation.
An anemometer measures wind speed.
A radiosonde attached to a weather balloon measures weather high in the atmosphere.
A satellite orbiting Earth takes pictures of clouds from space to help us see where and how fast clouds are moving.
A radar shoots a radio signal into a cloud to shows where precipitation is falling and how much. It can also spot severe storms and how fast they are moving.

Eyes and ears are probably the most accurate tools. Meteorologists all over the world observe clouds and precipitation, and relay that information and their measurements to other meteorologists throughout the world so we can know how the weather is changing from place to place.
Meteorologists plot their observations on a weather map every hour to see how fast the weather is changing, then forecast where those changes will occur next.

2. Synoptic Forecasting: This method uses basic rules that the atmosphere follows. Meteorologists take their observations, and apply those rules to make a short-term forecast.

3. Statistical Forecasting: Meteorologists ask themselves, what does it usually do this time of year? Records of average temperatures, average rainfall and average snowfall over the years give forecasters an idea of what the weather is "supposed to be like" at a certain time of year.

4. Computer forecasting: Forecasters take their observations and plug the numbers into complicated equations. Several ultra-high-speed computers run these various equations to make computer "models" which give a forecast for the next several days. Often, different equations produce different results, so meteorologists must always use the other forecasting methods along with this one. That's why when it comes to forecasting, machines can't do it alone; you always need humans involved.

Using all the above methods, forecasters come up with their "best guess" as to what weather conditions will be over the next few days.

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