Katia could be hurricane tonight, so let’s look at ‘recurving’


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Another one? Already?

Even as the East Coast struggles with the fallout from Hurricane Irene, the National Hurricane Center announced Wednesday that the tropical storm dubbed Katia is likely to cross over into official hurricane status tonight.

Currently moving toward the west-northwest at 20 mph, the Atlantic storm is expected to continue heading in that direction -- although at a slower pace over the next two days.


According to a report from the center, the storm’s maximum sustained winds have increased to near 70 mph; those winds are expected to continue strengthening over the next 48 hours.

But there’s a good chance that Katia will never hit land.

Hurricanes in the Atlantic do something called ‘recurving,’ which means they do not move in a straight line. Rather, they tend to move in what looks like a ‘C.’

Meteorologist Jeff Masters of Weather Underground explained to The Times that the trade winds off the African coast, which blow from the east to the west, generally push storms toward the U.S., but at the same time, the storm gravitates northward toward the pole.

Together, those two forces are creating the northwest movement we are seeing Katia do now. That’s the bottom half of the C.

But once the storm moves far enough north, it gets caught in the jet stream winds that move across North America from the west to the east, pushing the storm away from the coast. That’s the top half of the C.

Irene followed that same trajectory, but it did the C move as it headed up the East Coast. Katia could make its inevitable C entirely over water.


That happens all the time, Masters said. ‘More than half of all the Atlantic hurricanes never trouble anybody,’ he said.

‘We have a five-day track forecast that has it moving west-northwest and then it would spare the islands,’ Dennis Feltgen, a spokesman for the National Hurricane Center, told The Times. ‘But we’ll have to see how the weather patterns turn out upstream. Right now, there are too many balls in the air to predict what will happen.’


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-- Deborah Netburn