San Francisco Chronicle, 4-21-09:
Theories are swirling about the home run tally at the new Yankee Stadium about as fast as the wind that might be driving those balls out of the park.
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The 20 homers are easily the high for the first four games at a major-league park, according to the Elias Sports Bureau...<snip>
So why are all the balls flying out? The prevailing idea is that either a gap behind the bleachers in left or the open concourse is creating wind gusts that circle the park, in one way and back out the other. That theory picked up steam when the flags were blowing in much of the weekend.
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A source with the Yankees' organization said that the team believes the opposite will happen: The wind will subside when the old building is removed. The source said that the team was aware there might be a wind-tunnel effect. Some hitting coaches toured the stadium as it was being built and they noted "a jet stream."
MORE:
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/04/20/SPVO175MAV.DTL