Everyone remembers the weather fourteen years ago. Every remembrance story, every “where were you when” conversation, every newscast before the attacks mentions how the sky was a brilliant, deep shade of blue the morning the world turned upside down. However, had the sky not been as clear as it was that day—if the hurricane off the coast of New England hadn’t ricocheted toward Canada—it’s very possible that the weather could have permanently changed the course of both American and world history.

Understandably lost in that particular news cycle was the fact that there was a pretty scary looking hurricane sitting a few hundred miles off the Northeast coast on September 11, 2001. In the waning days of summer and long before social media came around, such a storm at the peak of hurricane season was unremarkable—if not unknown—to most in the country unless watches and warnings were hoisted along the coast.

Hurricane Erin was your classic Cape Verde system, a tropical cyclone that’s born from the waves of thunderstorms that push off the western coast of Africa in August and September. The storm strengthened to a category three with maximum winds of 120 MPH as it passed northeast of Bermuda, and started on a gradual weakening trend by the time it made its closest approach to the United States on September 11.

The preceding day was one of those murky, late summer days you’re used to on the East Coast. The high temperature at New York’s Central Park on September 10, 2001, was a balmy 86°F with heavy showers and thunderstorms in the area. Caught under one of those showers, the weather station’s rain gauge measured just over an inch of rain, all thanks to a fall-like cold front swinging through the area from the Midwest.

By the morning of September 11, the cold front had pushed out into the Atlantic Ocean, allowing high pressure to build across most of the eastern United States in its wake. The result was the first deep, gorgeous blue sky many folks had seen in a long time, as the sky had usually been obscured by layers of clouds or that ugly summer haze up to that point.

It was remarkable, so much so that the sky permanently etched itself in the minds of so many people that morning.

If the cold front had moved just a bit slower, the weather might not have been as beautiful as it was on September 11. The timing of the frontal passage cleared the skies and allowed the hijacked flights to depart without delay, also affording those bastards clear visibility along their flight paths. Not only that, but the cold front also kept Hurricane Erin from drawing closer to the United States, which likely would have affected both weather and air travel in New York and Boston as airlines prepared for a potential strike from a formidable hurricane.

Adverse weather that morning would have been the butterfly effect in action—one small change in the starting conditions could have had a dramatic impact on the end result. A simple, lingering batch of rain or clouds, or even the effects of Hurricane Erin in the megalopolis on September 11, 2001, could have changed both history and the world as we know it.

[Images: NASA, NOAA]

Email: dennis.mersereau@gawker.com | Twitter: @wxdam

If you enjoy The Vane, then you’ll love my upcoming book, The Extreme Weather Survival Manual, which comes out on October 6 and is now available for pre-order on Amazon.