A stark picture of how close Hurricane Irene came to being an even more serious disaster than it was emerges by overlaying a map of the storm track with a population distribution map. What made the storm as bad as it was had a lot to do with the fact that its trajectory took it over the most densely populated part of the country. Tropical storm level winds hit almost 63 million people – that’s a fifth of the country’s people directly affected by a single storm. But what made the storm less bad than it could have been had a lot to do with how narrowly the hurricane-force winds missed the most densely populated areas on the east coast. Only 1.9 million people were hit by such winds.
The graph (reflecting all countries affected by the hurricane) shows how close we came to having this be a much larger number. The blue line shows the number of people within a hundred miles of the storm’s eye – the strongest winds were largely within this band. The population curve, in blue, dips to its lowest precisely when the storm strength was at its highest. And the population curve spikes up, as the eye passes by the New York City metro region, as the storm strength curve is moving down steeply. If the storm strength curve had dropped just a little more slowly, which was well within the realm of possibility, we would have had an even bigger disaster on our hands.