THE WINTER CRUSHED the East Coast of the US. So let us crush your dreams of spring with a gentle reminder: Hurricane season is right around the corner. And the hurricanes that will slam into the Atlantic seaboard in just a couple of months are already glints in the eyes of storms-yet-to-be-born in Africa.
The Atlantic hurricane season officially kicks off in June, but it starts over the Sahara. In the Sudanese highlands—the same place the Nile begins—sun-heated air bubbles upward and condenses into mushroom-shaped thunderheads thousands of miles high. At the same time, enormous waves of air in the upper atmosphere push those storms west, toward the Atlantic. Most of these tempests will die on the coast. But some get second lives—as tropical storms or hurricanes. That turns out to be an important connection if you’re trying to predict hurricanes. New research shows that the temperature of clouds in those African storms could help meteorologists figure out which will mutate into coast-and-island-pummeling monsters on the other side of the ocean.
While these tall clouds are growing out of the high desert, a massive, oscillating atmospheric pattern called the Africa Easterly Wave is settling in thousands of feet above. It’s a vast, sine wave-shaped air flow that carries weather across the Sahara, east to west. When those Sudanese thunderstorms rise, they get caught up in the flow, off to drench Africa’s west coast. And there they stop; the Atlantic Ocean is cold, and thunderstorms thrive on heat.
But the Africa Easterly Wave persists, and sometimes so does the energy that used to be a thunderstorm. “And when the wave reaches the central part of the Atlantic basin, then some of the thunderstorms will start to develop again,” says Robert Rogers, a meteorologist with NOAA’s Atlantic Oceanographic and Meteorological Laboratory. Out in the mid-Atlantic, the water is warmer, the air more humid, and the wind stronger. And the Africa Easterly Wave’s undulations spin all those conditions into a nice cyclonic spiral.