It was lunch time and I was sitting in Buddy Guy’s Legends Club on Wabash Avenue just outside The Loop. Since the acoustic blues set hadn’t started, I began a conversation with another patron. We soon came around to baseball and the relative merits of the Cubs and the White Sox.

The fellow reached into his pocket and pulled out a pack of cigarettes. He carefully removed the clear cellophane cover off the box and held up the empty transparent enclosure. “Do you know what this is?” he said with a glint in his eye. “It’s the Cubs’ trophy case!”

Over the years the Cubbies have been the butt of oh, so many jokes. “Why are the Cubs just like Michael Jackson?” They both wear a glove, on just one hand, for no apparent reason. Rick Monday while with the Cubs was once asked to explain the team’s early season success. He answered, “It’s only June.”

Well, they aren’t joking anymore. Under their new field manager Joe Maddon, the Cubs went deep into the postseason last year and expect nothing less this year. So as we prepare for another year of October baseball in Wrigley Field, it might be interesting to look at the effects of weather in the Windy City in mid-October as opposed to midsummer.

This approach will be theoretical as opposed to data driven. Why? There isn’t much data on October baseball in Wrigley. As the North Side lament goes, “Any team can have a bad century.” Enough with Cubs put-downs.

The table below lists the average temperature and wind in Chicago for midsummer and mid-October. It is from WeatherSpark.com.

AVERAGE TEMPERATURE & WIND, CHICAGO Averages Mid-Summer Mid-October Average Temperature 73˚ 53˚ Average Wind Speed 8 mph 10 mph

There is one additional factor regarding the wind. It is far more likely to be blowing from the north and east in midsummer and more likely to be blowing to the south and west in October. Since Wrigley is aligned with center field almost exactly northeast of home plate we’ll use the simplification that the wind will be blowing in from center in midsummer and out to center in mid-October.

To see the effect of these weather differences, let’s look at three distinct hits. The hits are described below and in the table.

A line drive into the left field gap will have a high exit speed, a low launch angle and little backspin and no sidespin. The first fly ball will head toward center field with a moderate exit speed, moderate launch angle, and only backspin. The second fly will be hit toward left field with the same parameters, but some sidespin.

They are listed below.

THREE DISTINCT HITS Hit Type Exit Velocity Launch Angle Horizontal Angle Backspin Sidespin Line Drive to Left 105 15 -12 800 0 Fly Ball to Center 100 35 0 2000 0 Fly Ball to Left 100 35 -22.5 2000 600

Now, we’ll calculate the flight path of each of these hits using Alan Nathan’s Trajectory Calculator. We’ll do this with the average weather for midsummer and again for mid-October.

Here are the “slash lines” for each case. The first number is the distance the ball lands from home in feet. The second is the time in the air in seconds and the third is the deviation from the launch angle in degrees. That is, did the ball drift toward left field (negative) or right field (positive)?

THREE DISTINCT HITS, BY SELECT TIMES OF YEAR Hit Type Mid-Summer Mid-October Line Drive to Left 338/ 3.4/ -0.4 356/ 3.2/ +0.5 Fly Ball to Center 355/ 6.2/ 0 423/ 5.8/ 0 Fly Ball to Left 359/ 6.1/ -8.1 415/ 5.7/ -2.4

It is pretty clear that the wind blowing in during summer shortens the flight and the wind blowing out increases the distance. This is not news to the denizens of “The Friendly Confines.” For line drives the difference is fairly small, but for high fly balls it is very dramatic. A routine fly ball in early August could be a bomb in October.

There is a bit of confirmatory evidence from last year’s NLCS. The first two games, in New York, featured only four homers while the second two gameson Addison Street had seven. The third game had a 3 mph wind out to center and in the fourth game the wind was 8 mph out to right. Don’t be too impressed; the Small Sample Size Flu is rampant in the postseason.

Understand, the winds of Wrigley are fickle as I have written here at THT before. There is no guarantee that the wind will in fact be blowing out in October. It is just more likely to be so.

Weather also affects pitching. On April 10 this year Jake Arrieta pitched in the lovely 73 degree indoors at Arizona. The PITCHf/x data from that day can be used to find the average release point, start speed, initial direction, backspin and sidespin on Arrieta’s fastball, sinker and slider/cutter. Here are the numbers:

JAKE ARRIETA’S PITCHFX DATA, BY PITCH TYPE Pitch Type Start Speed (mph) x0 (ft) y0 (ft) z0 (ft) Vertical Angle (˚) Horizontal Angle (˚) Backspin (rpm) Sidespin (rpm) Fastball 94.4 -2.46 55 6.31 -3.2 176 1810 -1240 Sinker 95.0 -2.52 55 6.28 -3.1 176 1600 -1660 Slider/Cutter 90.4 -2.70 55 6.25 -2.7 177 750 750

Using these values in the Trajectory Calculator we can find the location of these three pitches at home plate for the midsummer (red) as well as mid-October (orange). The size of data point is roughly the actual size of a baseball.

The orange balls are pitched against the wind that is blowing out to center field, while the red balls are pitched along with the wind that is coming in from center. The results may seem backwards because one might guess that a pitch thrown into the wind would slow down more quickly, allowing gravity to cause it to drop more than a pitch carried along with the wind.

This illustrates the magnificent skill pitchers have to create forces on the ball caused by the spin they put on it interacting with the air. The size of the force caused by air (Magnus force) depends upon how much air the ball goes through on its way to the plate.

If the ball is traveling into the wind it passes through more air and feels more force, while the opposite is true if it is traveling along with the wind. Basically, a fastball thrown into the wind will have more “hop” than a fastball thrown with the wind. This illustrates that pitchers must adjust their release point depending upon the wind in which they have to pitch.

So the difference between the dog days and the postseason at Wrigley isn’t just the fact that fly balls can become homers. In fact, a devastating slider on the inside corner can become an easy take. It may not be just the curse of the Billy Goat that creates the otherworldly goings on throughout the Cubs’ postseason history. It might be that there is some physics behind it.