Why do weather predictions differ

However, a day—or longer—forecast is only right about half the time. Meteorologists use computer programs called weather models to make forecasts.

The atmosphere is changing all the time, so those estimates are less reliable the further you get into the future. A seven-day forecast is fairly accurate, but forecasts beyond that range are less reliable. Some of the information needed to make a weather forecast comes from environmental satellites. This means they can collect near-continuous images over the same area.

Because they focus on one spot, they can provide up-to-the-minute information about severe weather. This information helps forecasters understand how quickly a storm, such as a hurricane, is growing and moving. Credit: NOAA. They zip around our planet from pole to pole 14 times per day. Because they orbit while the Earth is rotating below, these satellites can see every part of Earth twice each day.

By watching these global weather patterns, polar orbiting satellites can help meteorologists accurately predict long-term forecasts—up to 7 days in the future. That allowed meteorologists to plot weather maps and see weather systems moving from place to place.

That improved the accuracy of forecasts. During the s, meteorologists developed even better tools for observing and predicting the weather. Special instruments measure weather in the atmosphere far above the ground, and satellites orbiting the Earth send back images of the weather over large areas. In addition, computer models are now being developed for weather forecasting.

In a computer model, the important processes of the weather are built into the model. The model starts with the present weather and tries to simulate how the weather will develop in the future. Today's computer models do a very good job of predicting the weather for the next few days. Subscriber Account active since. It sounds like a silly habit, but it also raises a good question: Why do weather forecasts vary depending on which app you use?

The forecast process starts with data and observations that come from weather stations around the world, satellites, radar, reports from volunteers, and weather balloons that collect information about the atmosphere, such as humidity, wind speed, and temperature. All of these measurements are fed into supercomputers run by the United States government and other countries. Supercomputers take those initial conditions and then use mathematical equations to come up with a forecast.

There's no perfect algorithm because the Earth is so big that's impossible to have observational data for every parcel of air. Since each computer model uses a different mathematical formula, each weather forecast may be slightly different.

The outputs, or "solutions" to the equations, are typically maps that show things like pressure, temperature, and precipitation in a certain geographic area. Supercomputers with more power will produce higher resolution maps, which means they are more accurate.

After you get the outputs, the meteorologists and their knowledge of the local weather patterns all come into play, Maier adds. Weather data is provided free by the U.