Today’s Wonder of the Day was inspired by Melinda from Chula Vista, CA. Melinda Wonders, “How do forecasters predict weather? ” Thanks for WONDERing with us, Melinda !

You check the clock and realize you're running late. The school bus is going to arrive any minute now. You grab your backpack and head for the front door, but you're stopped by a parent's voice reminding you to grab your coat and an umbrella.

What's the deal? You look out the front door, and it doesn't look cold or rainy. Before you can even protest, you're told that the temperature is going to drop when it begins to rain later this afternoon. Can your parents see into the future? Do they have a crystal ball? Not likely! They probably just checked the weather forecast.

Weather forecasts help us prepare for the future, whether it's a few hours from now or the rest of the week. Not only do they warn us of potentially-dangerous weather headed our way, they also give us an idea of what to expect in terms of temperature and chance of precipitation, so we can dress and equip ourselves appropriately.

The people who study the weather and put together forecasts are scientists known as meteorologists. Have you ever seen a forecast that called for lots of snow? You might have gotten excited, anticipating a snow day and the chance to do some sledding. Unfortunately, you woke up to clear skies, no snow, and a full day of school ahead. What happened? How could the weather forecast have been so wrong?

Weather forecasting is not a perfect science. Forecasts are a prediction based upon an educated guess. Since there are a wide variety of factors that go into a forecast, it's possible for meteorologists to guess wrong from time to time. Fortunately, modern technology has allowed forecasters to become much more accurate over the last decade.

Today, meteorologists use complicated mathematical equations to help predict the weather as part of a process known as numerical forecasting. Numerical forecasting requires powerful supercomputers and tons of observational data from land, sea, and air weather stations around the world.

Where does all this data come from? Sometimes it comes from regular people like you! Many people create their own backyard weather stations with thermometers to measure temperature and rain gauges to measure precipitation. They can report their observations to local meteorologists to help improve local forecasts.

Technologically-advanced weather stations are established by meteorologists all over the world. They collect and share data to help improve forecasts. Some of the tools they use include barometers that measure air pressure, anemometers that measure wind speed, Doppler radar stations to monitor the movement of weather fronts, and psychrometers to measure relative humidity.

To get data from the seas and the upper atmosphere, data-collection tools and instruments may be attached to ships, airplanes, and even buoys in the middle of the ocean. Weather balloons and weather satellites also provide observational data that can be used on a global scale to spot weather trends for large areas.

All these different types of tools around the world produce millions of pieces of weather-related observational data every single day. Supercomputers, such as those at the National Centers for Environmental Prediction in Camp Springs, Maryland, process that data to produce forecasts based upon complicated mathematical models. Current data is compared to similar patterns that have occurred in the past to determine what will likely happen in the future.

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