Understanding the meteorology of a flying balloon can help baseball teams


As of this writing, the opening of the World Series is only a few hours away. Two Major League Baseball (MLB) franchises, the Los Angeles Dodgers and the Boston Red Sox, are playing in the fall classic. Both teams play in outdoor stadiums, so there is always a chance that the weather is a factor. However, I decided to go beyond the standard story of how the weather might affect the World Series. As an atmospheric scientist, I thought it would be interesting to explore the meteorology of real baseballs in flight and the innovative capabilities of a new company called Weather Applied Metrics.

John Farley / WAM

To explore this topic, I had a chat with John Farley, CTO for Weather Applied Metrics (see this link for an informational video). The company quantifies weather impacts on baseball (and sports in general) using computational fluid dynamics (CFD) modeling, standard trajectory physics, and other weather analysis. According to Farley, the company has a team of six: two with doctorates – one is a retired professor of meteorology, one is a CFD engineer, a meteorologist with a master’s degree, a physics student, a CEO of a Silicon Valley company and a San Francisco Bay Area Meteorologist. Farley held out his hand to me and I was immediately mesmerized. In my university research, I study urban meteorological processes and I was therefore familiar with the use of numerical modeling of fluid dynamics (good tutorial on this link) to simulate the flows around buildings or to follow the flows hazardous material tracers. There are many applications for CFDs, but I never thought it would be in a baseball stadium. Weather Applied Metrics has installed its beta site at Columbia Fireflies Stadium. The Fireflies are the single A affiliate of the New York Mets in Columbia, South Carolina. Farley told me,

You might remember Tim Tebow hit a home run on his first at-bat with the Fireflies. The weather that day helped carry that ball about 15 to 18 feet and it cleared the fence a few feet. So, without the weather, this probably would have been a warning trail. Last June we installed our technology in an MLB park and are now in the final stages of making a deal with them for the 2019 season.

I was so fascinated with what this company was doing that I conducted a question and answer session with Farley. Our conversation is summarized below.

Dr Marshall Shepherd: How does the weather affect the trajectory of baseball?

John Farley: If the wind is blowing hard, this is the biggest impact. A headwind, combined with a downdraft, can shorten a ball hit against the wall up to 60 feet. A tailwind, combined with an updraft, can stretch it up to 45 feet. Since baseballs absorb moisture from the air (they are hygroscopic), the difference in distance between very dry air and very humid air is about 50 feet. This is because a wet ball is slightly heavier and more spongy, so it doesn’t come out as quickly. On a hotter day, the air is less dense, so a bullet can travel up to 30 feet more, compared to a cold day. Atmospheric pressure directly affects density. Thus, bullets struck at high altitudes travel much further. In the graph above, our analysis is an example of a crosswind over a major league stadium. With the resulting downdraft and headwind in the right field, the ball’s flight is shortened by about 30 feet.

Dr Marshall Shepherd: Can this have a significant impact on the results and is there a way to determine it?

John Farley: Yes. Our real-time display at Fireflies Stadium in Columbia, SC shows how much weather conditions impact the distance of an average ball hit to the fence of the outfield (averaging 375 feet). Blue numbers are added feet. Red numbers are subtracted feet. Here are some examples of games. The arrow on the marble indicates the prevailing wind. In this smaller stadium, the prevailing wind is very representative of the winds on the flight of the balloon.

John farley

Dr Marshall Shepherd: How do you use computational fluid dynamics (CFD) modeling to study baseball?

John Farley: CFD is necessary because the wind flow inside the stadiums is very complex and often very different from what the flags show at the top of the stadium. Plus, what’s missing from all of the baseball trajectory analysis we’ve seen is the vertical wind (as meteorologists, that’s all we think about!). And there is a lot of vertical wind inside the stadiums, which has a big impact on the flight of the ball along its entire trajectory. Prevailing winds (see graphic below) blow over a stadium in one direction, but field-level winds do the exact opposite, and there is a lot going on in between. We model the wind field up to every square foot over the entire area where a ball could fly. Then we use these winds for our 3D trajectory model in 0.001 second increments.

John farley

Dr Marshall Shepherd: Why do you do that?

John Farley: We are weather and sports geeks and we are very curious! Why else would we do this? 😉 As meteorologists, we have always known that the weather has a huge impact on sport. Now we can tell you exactly what’s going on with each bullet.

Farley and his colleagues may be aware of something, but only time will tell. He provided me with a summary of how Weather Applied Metrics (WAM) illustrates the impact of weather on baseball. Data was collected for all home games of the Columbia South Carolina Fireflies for the 2016 season. Mass play statistics show some pretty compelling impacts on points per game, points won per game, homers per game and hits per game.


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