Behind the forecast: How meteorologists predict the weather

How do meteorologists predict the weather? Here's a breakdown of the whole process.

Posted: Nov 25, 2020 11:37 PM

EUEGNE, Ore. – Our StormTracker 9 weather team comes on the air seven days a week to bring you an accurate forecast, but there’s a lot that goes on behind the camera before the forecast gets to you at home.

In order to forecast the weather, you need to know what’s happening right now -- both on the ground and thousands of feet up in the atmosphere. 

We gather these upper-air and surface observations from hundreds of weather stations located around the world. These surface stations are usually located at airports and they are called Automatic Surface Observing Stations (ASOS). These stations are equipped with sensors to measure wind speed and direction, dew point, air temperature, precipitation amount, visibility, cloud height, thickness, and air pressure.

Weather balloons get launched every day, twice a day -- morning and night -- and they will go to altitudes of 100,000 feet, almost three times the height of a commercial airliner, to gather weather information from the upper-most regions of the atmosphere.

“The weather is three-dimensional, so we need to have observations as high up as you can go,” said Tyler Kranz, a meteorologist at the National Weather Service in Portland.

Kranz explains the process that follows after these observations are gathered.

“All of that data gets ingested into numerical weather models which we then can use to help us predict the weather,” he said. “That data is assimilated into our models which improves their output so we can use them to give us a good forecast.”

Once the forecast models have been released, it is available to the meteorologists on our StormTracker 9 weather team. Our job is to interpret what the models are saying.

“The reason we need to look at all the different models is because some are going to be right and some are going to be wrong, and then it is our job to take a look at what they’re showing, and choose and think which one is going to be the most right,” said meteorologist Andy Moffit.

Meteorologist Marisa Woloszyn said her experience as a meteorologist in Oregon has allowed her to make a judgment call on when models are most likely to be wrong.

“When a storm moves through and brings us rain, usually the next day the models say it’s going to be sunny, but I have learned over many years that rarely happens. I have learned that we’re not going to have sunshine, we’re most likely going to have fog,” she said.

Putting together a solid forecast takes one to two hours, and the next step is to make our weather graphics which you see on TV. It works like a PowerPoint presentation. We line up the graphics in the order that best tells the weather story for the day.

“Yes, we know all the science and all that stuff, but being on TV the thing that we really try to accomplish is how do we communicate this to viewers,” Woloszyn said.

We try to have the forecast be as relatable as possible and communicate it in a way that is conversational.

Predicting the weather and properly communicating it can be a tricky task! Based on recent studies, it is estimated that a three-day forecast is around 80 to 85% accurate, and of course those numbers drop off the further out in time you go.

So how do we improve the forecast? The quick answer is we need to gather more observations, and we need researchers improving the models.

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