The science behind the 7-day forecast

Today, meteorologists can put together a reliable forecast up to eight or nine days out/Matt Mackie (WGXA)

Severe weather season has passed its peak in Middle Georgia. Starting June 1st, we’ll be in Hurricane Season, making the forecast is more important than ever. So let’s talk about the science behind the seven day forecast: What goes into making the WGXA Weather forecast? Why do we get the forecasts wrong sometimes? And how are our predictions getting better?

According to Dr. John Knox at the University of Georgia, every forecast you get - On TV, on your phone, on the Internet - can be traced back to something called numerical weather prediction. That process takes incredibly complex equations that describe the atmosphere and breaks them down into simple math. Cutting edge supercomputers then run those numbers and predict where weather features will move over the next few minutes or the next few hours. They do those calculations over and over again until a full forecast is made.

"It is one of the most computer-intensive projects that exists in human civilization," said Knox.

Then, meteorologists use their experience to decide how accurate these predictions are, and what will actually happen in your neighborhood.

But with all these resources going into the forecast, why do we get it wrong sometimes? Part of it is that we’re still learning about the atmosphere.

“Meteorology is actually a young field,” Knox said. "It its modern, scientific incarnation. It's just a little more than 100 years old."

Another problem? Even with weather satellites that send back terabytes of information, there are still some parts of the atmosphere that our weather observation network misses.

But data and better equations can only get you so far. Even if meteorologists had everything they needed, predicting the future will always have its limits.

"Even with perfect, as good as we can get forecast equations and forecast data, forecasts would go out of tune at about the 14-day mark. About two weeks of skill is our limit, perhaps eternally," Knox said.

In the meantime, the range of our ability to forecast is racing towards that two-week limit. Today, meteorologists can put together a reliable forecast up to eight or nine days out. They’ve added one day to that total every decade over the past 50 years.

"Meteorologists can get concerned about a situation that's going to arise in maybe a week, almost a week. When I was a kid in the 1970's, we didn't have that ability at all. We would be blindsided by something that was coming a week later,” Knox said.

And that means you and your family get more warning ahead of dangerous weather.

After a record-breaking 2017 Atlantic Hurricane season, improvements are coming to the National Hurricane Center’s well-known forecast cones. Those cones show where forecasters predict the center of a hurricane will track over the next several days.

The area covered by the cone grows wider and wider the further you go from a storm’s current position. That’s not because the storms are expected to grow in size (remember, they’re predicting only where the center of the storm will go), but because there’s more uncertainty as to where the storm will go.

The width of those cones is based on how accurate hurricane forecasts have been over the past several years. Sid King with the National Weather Service in Peachtree City says we’re getting better at those predictions.

While hurricanes and tropical storms lose strength as they move inland, they can still bring dangerous weather to Middle Georgia. This week is National Hurricane Preparedness Week. The National Weather Service recommends you check to see if you have enough insurance coverage to replace your home and car ahead of hurricane season.

The forecast we bring you every day might not always be perfect, but it’s come a long way from humble beginnings one hundred years ago. With all the research and technology going into the forecast, it’s getting better at lightning pace.

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