This will be an interesting week at Target Field.
Not only are the Yankees coming to town, but the weather will be warm and somewhat humid tonight, with much less humidity later in the week. Warm and humid weather is ideal for maximizing ball flight. It's a home run hitters dream.
The physics of baseball flight is important when it comes to determining whether Target Filed is a pitcher's or hitter's ball park. The site specifics, orientation and stadium structure are also important. So far in 2010, Target Filed is definitely playing as a pitcher's ball park.
With just a 1.38 home run per game average, Target field ranks 25th out of 30 major league stadiums so far this year in home runs per game according to the hitrackeronline web site.
Judd Spicer with City Pages and I recently chatted about how weather affects baseballs at Target Field, and why it may be a pitcher's ball park in spring and fall...but morph into a hitter's park when it's warm and humid in summer.
You can read Judd's piece here, but here are a few key elements from our conversation.
Three main weather factors affect a baseballs flight. Air temperature, humidity, and wind.
In the spring in Minnesota we tend to have higher air pressures and colder temperatures. Temperature and air pressure are inversely proportional. One goes up, the other goes down. As the temperature falls in colder spring weather in Minnesota, the pressure is usually higher. So, meteorologically speaking, air is denser at higher pressures. That creates more friction on the ball in flight. All other things being equal: if Justin Morneau cranks one good with a home run swing, that ball will fly farther in warm, humid (less dense) air.
Air pressure depends on elevation above sea level. The higher you are the lower the air pressure -- that's a constant fact in the state of the air pressure. Higher elevation means lower air density, so as a result baseballs will travel farther. Colorado is the highest elevation park in Major League Baseball. The 20th row in the upper deck at Coors Field is said to be exactly 5,280 feet. Arizona is second (1090 feet) and Atlanta is third at 1050 feet.
At about 840 feet, Target Field is the fourth-highest elevation above sea level stadium in MLB. There was a study done at Middlebury College in July of 2005 that suggests that for every 500 feet you go up above sea level, you add about 10 home runs at your stadium every three years. So if you take that theory, Target Field would have about 3 to 4 more home runs every year than you would compared with the same stadium at sea level.
But here's the thing about Minnesota: we tend to have higher air pressures -- especially in the spring and fall -- than these other stadiums might in other parts of the country. Our weather systems here also affect that. We get colder air and get higher pressures than in Phoenix or Atlanta, and even in some cases Colorado. So that tends to counteract the higher elevation a little bit.
For the spring and fall in Minneapolis, the prevailing wind is from the northwest. At Target Field, that means the wind is blowing out. A northwest wind blows from the third base line out toward right center field. That's most of the time, if you average it out. That probably holds true for April and May, and then again in September."
Even though the winds are blowing out, a northwest wind is usually a cold wind in spring and fall so baseballs are still fighting the friction of the cooler, denser air.
Another interesting factor about Target Field is that the stadium structure and canopy covering from the first base line to the third base line is a huge wind shield. When the wind is blowing from the north or west, it is reduced a little bit by the high profile of the stadium behind home plate. So a wind blowing out at Target Field may not help a baseball as much as it would in a more open stadium.
In the summer the prevailing wind here comes from the southeast which is, basically blowing in from right center field. That's pretty much for June, July and August.
Humidity affects the flight of a ball as well. Higher humidity air is less dense air, so as a result balls will fly farther in humid air, all other things being equal. Water vapor is lighter than nitrogen and oxygen. But here's the interesting thing about Target Field: Again, the warm and humid winds are southerly, those are blowing in. So on a warm, humid night if there is a breeze, it's generally going to be blowing into the ballpark. So, it counteracts; it's fighting each other. It's almost like the perfect set of circumstances for long home runs to rarely occur at Target Field.
So here's my take on the perfect conditions for long home runs at Target Field.
-Warm humid weather (temps in the 80s or 90s with dew points above 60 degrees)
-Little wind, or a slight southwest breeze (blowing out toward left field)
It will be interesting to see how many home runs per game are hit this week vs. The Yankees. The average so far at Target Field is 1.38 per game. My forecast for the series vs. the Yankees is for 2 to 3 homers per game. One reason is the Yankees are coming to town. The other is this may be the best home run weather so far for Target Field this year.
Sunday was a preliminary test with the temperatures in the 80s and dew point in middle 60s. Seemed to be offset by the brisk southeast breeze as you noted in the write-up.
"My forecast for the series vs. the Yankees is for 2 to 3 homers per game."
Does your forecast include how many hits were 'almost' home runs? i.e. how far short will a ball fall in unfavorable air? How many fly balls were caught on the warning track? In better conditions, would all of those sail over the wall?
I think the evidence suggests you could easily add 10 feet+ to most balls in warm humid conditions vs. cold and dry.
So yes, many balls caught on the track would have cleard the fence in less dense air.