Quiet hurricane season defies predictions
The hurricane predicting business this year was a bust. Even forecast guru Bill Gray of the Tropical Meteorology Project has said so.
Federal meteorologists, academic researchers and private companies each called for a busy year back in the spring. All the soothsaying signs were in place — warm seas, weak shear winds and so on. Even as the season stayed relatively calm through August, they called for a late surge.
Now, with the season winding down, few storms and not a single major hurricane have formed.
So what happened? Maybe they just didn’t put on the right pairs of glasses.
About 10 years ago, tropical researcher Jason Dunion, of University of Miami, Fl., broached the idea that a huge, unregarded factor in hurricane formation was dusty air blown into the Atlantic Ocean off the Sahara Desert. That dry air, whirled into the cyclones, disrupts and weakens them, he said.
Today, Saharan dry air is a staple of hurricane forecasting. And this year, the Saharan winds blew farther southwest than usual, right into the zone where African monsoons blown into the Atlantic form tropical waves that become hurricanes — the notorious Cape Verde storms. Meteorologists in West African nations called August the driest they had ever seen, Dunion said.
At least two other things happened:
The air carried dust all the way across the Atlantic into Brazil, then into the Caribbean where it disrupted storms there.
A pocket of cooler water in the ocean off Portugal weakened storms that moved north.
Neither of the two were factored into computer modeling for predictions.
In other words, forecasters are finding — yet again — that there’s still a lot to learn about the complex, ever-changing, interrelated weather phenomena that create hurricanes. Dunion, for example, is now studying a weird, newly discovered phenomenon in tropical storms.
“The storm exhales and expands every night at sunset. It almost breathes,” he said. The significance isn’t clear yet, but the expanded clouds could well be pulling in more of factors like winds or water temperatures that strengthen or weaken a storm.
It took infrared satellite imagery analysis to find it.
“We didn’t see it before because we didn’t have the right pair of glasses,” Dunion said.
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