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Spaghetti Baseball: predicting prospects is like predicting the weather

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photo from Wikipedia Commons

Saturday, June 13, 1976. I was eight years old. My parents decided that I was old enough to spend time away from home, so it was off to summer camp at the Episcopal Center for Camps and Conferences north of Des Moines.

The first thing I remember that Saturday morning was walking out of the house into what felt like a blast furnace: it was hot, humid, windy.

Mid-June is the heart of tornado season in central Iowa, and on the afternoon of June 13th the atmosphere would explode.

On the way to camp, we drove through a tremendous thunderstorm including large hail and fierce winds. Eventually we broke out into a clear area of the storm. And off in the distance, we saw this:

The person who took this video had a very similar vantage point to ours. and was likely driving along the same highway as we were.

It was an F5 tornado, and one of the most powerful ever recorded in modern times. Dr. Theodore Fujita, renowned tornado researcher and developer of the famous Fujita Scale for tornado damage, once remarked that this particular tornado was the strongest he had ever studied. The tornado hit a small town called Jordan, annihilating it.

Remarkably, no one was killed. The tornado stayed in rural areas, which was most fortunate. A shift of just a few miles would have brought this monster through the heart of Ames, Iowa.

Witnessing this thing had quite an impact on my impressionable young mind. I decided that I wanted to be a "weatherman," a meteorologist. I read everything I could find about severe weather, thunderstorms, tornadoes. It was one of my biggest passions as a child and teenager, along with baseball.

Unfortunately, once I got into high school, I discovered that I was not very good at advanced math (I'm still not). And I was especially bad at physics. I could understand the general theory behind everything, but when it came down to pencil and paper and formulas and a scientific calculator, my mind would blank. I eventually came to the realization that I wasn't cut out to be a real meteorologist, so it just became another hobby.

So what does any of this have to do with baseball?

Weather is a natural system. It is somewhat predictable, if you have enough data. Baseball players (and human beings in general) are also natural systems, and with enough data they are also somewhat but not entirely predictable.

Meteorologists use computer models when making their forecasts. Each model uses a different set of assumptions in taking a data set and projecting it out into the future. If you poke around the internet, you will find charts like this one:


Wikipedia Commons

This is a chart of "model output ensembles," commonly called a "spaghetti diagram." Each line on the chart represents the output of a different computer model, in this case projecting the flow of the jet stream. A meteorologist making a forecast will consult different models that use different assumptions, to get an idea of the possible outcomes of the current situation.

There is more to it however.

No good meteorologist will make a forecast based on one computer model alone. She will sift through all of the data and model outputs and make her own judgment. There is a place for intuition, instinct, "gut feeling" if you will. I personally believe that what we call "intuition" is often an expression of subconscious pattern recognition on the part of the human mind.

Baseball player prediction systems like Steamer or ZIPS or a bunch of other stuff you can find at Fangraphs operate on the same basic assumption as weather models. They are less complex, of course, since there are fewer variables to consider. The parallels can only be drawn so far between weather and baseball, but they are there.

Of course, even the best model and the best human forecaster screws up sometimes. "High Risk" severe weather days sometimes result in nothing but a bit of wind and lightning. Sometimes all the known parameters come together, but something just isn't quite right. . .perhaps the wind shear was less than forecast, or a cirrus shield prevented the atmosphere from destabilizing.

In baseball, this is the "can't miss" prospect who misses, sometimes due to injury, sometimes due to a hidden flaw eventually exposed, or a seemingly small issue that turns out to be huge, and sometimes for no obvious reason at all.

Predicting the weather and predicting prospects: we are better than we used to be at both, but they will still humble you.

(This is an edited and extensively revised version of an article originally published in March of 2005)