MIAMI, FL – The spiral shape of a hurricane is perhaps its most recognizable feature, except when it intersects the equator.
That’s what happened when a tropical depression turned into Hurricane Shemp and veered south in the Atlantic Ocean. It straightened out, a phenomenon never before seen by meteorologists.
Thanks to the Coriolis effect, tropical cyclones rotate counterclockwise in the northern hemisphere, and the clockwise in the southern hemisphere. Earth’s rotation tugs unevenly across the span of a system, causing it to spin.
Not so at the equator, where a hurricane will simply line up, postponing rotation until it can get to a more convenient location. The result, for a time, is an orderly windstorm that’s easier to predict.
“That buys us time, because forecasters know what path it will be on for a few days at least,” said Koby Dreher, an expert on every South Atlantic hurricane in recorded history. “When they decide to get off the treadmill, though, it’s another story.”