The answer, my friend, is blowing in the wind. The answer is blowing in the wind...
Last season, the Cubs ties for the 3rd best road record in the National League, posting a 41-40 mark that came in behind St. Louis's 50-31, behind Philadelphia's 42-39, and even with Arizona's 41-40. However, the Cubs didn't play well at home going only 38-43 at the Friendly Confines, making them one of only two teams in the majors to post a record below .500 at home and above .500 on the road (the other was the Diamondbacks). The question is why was there such a discrepancy between the Cubs performance on the road and at home?
One possible answer to this question is suggested by dividing up the Cubs home games into two groups: those played with the wind blowing in and all the others. According to Dave van Dyck, the Cubs went 19-26 at Wrigley when the wind was blowing in last season, which means they went 19-17 in their remaining home games (those played with the wind blowing out or across the field). Add these games to the Cubs road record and you'll find that for all games except those played with the wind howling in off Waveland and Sheffield, the Cubs went 60-57. If they had played at a similar level in those games with the wind in their faces, their final record would have been 83-79, 4 games better than their actual record of 79-83. Thus, it seems the Cubs could have been a .500 ballclub if they had simply been as good with the wind blowing in as they were in the rest of their games.
Digging a little deeper into the past, we see that this trend held for 2004 as well. According to the statistics collected by Andy Rutledge of View From the Bleachers, the disparity in 2004 was even greater: that season the Cubs went 16-19 at home with the wind blowing in and went 29-18 in all other games played at Wrigley (the Cubs played 82 home games in 2004). The Cubs road record in 2004 was 44-36, meaning they went 73-54 in all the non-wind-in-at-Wrigely games. If they had sustained that win rate (.574) for the games played with the wind blowing in at Wrigley, their final record would have been 93-69, 4 games better than their actual 2004 record (89-73) and good enough for that year's NL wild card spot.
This leads us to another obvious question: why is it that the Cubs fortunes are subject to the direction of Chicago winds? One possible answer is that the Cubs reliance on the long ball to score runs and their inability to score runs in any other fashion would lead to such a split in results. When the wind blows out, the power in the lineups the last two years manifests itself in wins but when the wind blows in the team struggles to score runs and loses "close" ball games. One nice thing about this theory is its explanatory power - the last two years the Cubs have had a worse record than one would expect based on the number of runs they scored and gave up. The "wind theory" could explain this, as it is possible the Cubs won a lot of blowouts when the wind blew out and lost a lot of close games when the wind blew in. If this theory is correct, it seems that if the Cubs ability to manufacture runs when the wind blew in was as good as their ability to hit home runs when the wind blew out, they would have been a .500 team last season and a playoff team in 2004, the result of 4 game improvements in each of those seasons.
This is why today's win was so encouraging - the Cubs beat one of their divisional rivals, a team known to play sound fundamental baseball, in a game with the wind howling in from left/left-center field. Even more encouraging was the convincing fashion in which they won the game. The Cubs looked to be the superior team in their ability to manufacture runs, their defensive prowess, their sound baserunning, and their pitchers' collective willingness to throw strikes and dare the other team to put the ball into play. On one hand, one doesn't want to get too excited about one game... except the other hand holds the tantalizing knowledge that the 2006 Cubs are constructed better than their predecessors to play in these conditions. The upgrade of Holly-Dubois/Patterson to Murton/Pierre is magnified when the wind blows in. Murton and Pierre can hit for average, get on base, and run the bases better than their previous counterparts. Furthermore, one would not expect a decline in the Cubs ability to win on the road or when the wind blows out, as Murton and Pierre should be able to put up better aggregate power numbers than their 2005 counterparts. (Its also important that Pierre should get on base much more often than Corey did, meaning the HR's hit when the wind blows out should count for more with Pierre in the lineup.) If their addition to the lineup allows the team to play as well when the wind blows in at Wrigley as they do in all other conditions, it should add ~4 wins to the team's final record. The pleasantly optimistic part of adding these 4 wins is it doesn't take into account the extra wins the Cubs get by replacing Holly/Dubois/Patterson for all the other games, nor does it include a full season or Ramirez or the upgrades to the bullpen made in the offseason.
We should all be paying attention to the Cubs fortunes when the wind blows in this April - success could be an indicator of good things to come the rest of the season. Improving the team's record in these games will not get the Cubs to the playoffs all by itself, but it certainly will help a great deal. I for one think if the Cubs can play sound, fundamental baseball like this the whole season they will end up winning a tight, 3-team race for the divisional crown.