With three hurricanes currently battering the Carribean and the continental US, scientists and politicians have been throwing a lot of measurements around: rainfall, diameter, category, death-toll. But what do those measurements mean, and how do Harvey, Jose and Irma really stack up when compared to previous storms?
There are two common ways we measure a hurricane’s size and power: diameter and the Saffir-Simpson scale. Diameter measures how big a hurricane is, while a hurricane’s category on the Saffir-Simpson scale measures wind speed (with Category One being the slowest speed and Category Five being the fastest).
For all of their destructive damage, Jose and Harvey are relatively small, both of them measuring at around 200-250 miles in diameter. For reference, a 200-mile-wide storm could handily cover Arkansas, with room for more than half of Mississippi. However, they’re both relatively powerful, clocking in at a Category 4 (winds of 130-156 mph). Combined with Harvey’s heavy rains, these winds have caused outsized destruction.
Hurricane Irma, while far from the biggest storm to hit the US, is bigger, approximately 400 miles around as of September 15th. That’s big enough to cover Texas, part of Kansas, and most of New Mexico. It’s the biggest of the “Big 3” 2017 hurricanes, but it’s less than half as big as Hurricane Sandy, the largest hurricane to hit the continental US (approximate diameter below).
But Hurricane Sandy was a Category Three, with winds barely hitting the speed limits on most American highways. Irma’s Category 5 winds (170 mph) are faster than most people would feel comfortable going on the Autobahn.
The world’s largest recorded storm was Typhoon Tip (1979), maxing out at approximately 1,250 miles in diameter as it skimmed Japan and the Philippines, killing 99 people (approximate diameter below)
However, size isn’t the only thing that matters when it comes to measuring a hurricane’s destructive potential. Hurricane Katrina, less than a third of its size, killed 1,833. This was both because Typhoon Tip burned much of its energy over the Pacific and because of the poor crisis management that occurred during Katrina.
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