ROBERT SIEGEL, host:
We usually bring you news about things that happen - wars, coups, leveraged buyouts, dogs that bite. Well, today we'll report on something that did not happen - dogs that did not bite.
MICHELE NORRIS, host:
Namely, hurricanes. Today, it marks the last day of this year's hurricane season, and not one hurricane hit the U.S. Now, that was a relief after last year when Rita, Katrina and Wilma brought death and destruction to the Gulf Coast.
SIEGEL: This year, gale force winds did not howl. Storm surges did not trample fragile coastal wetlands. Dream houses on the beach were not reduced to match sticks.
NORRIS: Palm trees did not snap when the storm made land fall. Levies and floodwalls were not breached or overtopped or scoured.
SIEGEL: And thank heaven for that. Basements and homes did not fill with water, and shingles did not fly from rooftops. Sales of plywood were stable.
NORRIS: Last May, weather experts had predicted a much more menacing hurricane season.
NPR's John Hamilton explains why it never came to be.
JON HAMILTON: The past few years have been humbling for the people who tried to predict hurricane seasons. Scott Brown is a meteorologist at NASA Goddard space flight center in Maryland.
Mr. SCOTT BROWN (NASA Goddard Space Flight Center): For several years, they had underestimated the seasonal activity. This past year, they thought it would be another active season and they overestimated the activity. So it shows that it's a science still in its early stages.
HAMILTON: Brown says one reason this year wasn't a repeat of 2005 was water temperature.
Mr. BROWN: The average ocean temperatures in the tropical Atlantic in 2005 were up to one to two degrees warmer than they were in 2006, so that meant that there was a lot more fuel for storms last year than there was this year.
HAMILTON: Another factor was weather conditions off the west coast of Africa - that's where many big hurricanes are born. Greg Jenkins is a meteorologist at Howard University in Washington, D.C., who spent part of this hurricane season in Africa. He was studying the development of weather systems known as waves.
Mr. GREG JENKINS (Howard University): Yeah, the waves were coming off. They were vigorous, but they would often get squashed.
HAMILTON: Squashed by winds coming out of the west. These winds tend to keep waves from organizing into large rotating storms that may eventually become hurricanes. In 2005, these winds were coming out of the east. Jenkins says NASA's research over the summer also found evidence that something else was preventing hurricanes from forming - dust. He uses a computer animation to explain. It shows satellite images in an area where storms often gain strength.
Mr. JENKINS: We're looking at the eastern, kind of central Atlantic here. And so this milky color here is dust, right. And to consistently see plumes of dust coming off of Africa during the months of August and then continued into September.
HAMILTON: Scientists think clouds of dust tend to weaken storms. Last year, the air off the African coast looked a lot clearer. Despite the dust, colder water and unfavorable winds, five hurricanes did form in the Atlantic this year, but most of them didn't reach the U.S., Jenkins says.
JENKINS: They all turned off to the north and east, just like an angel was watching over the U.S.
HAMILTON: Jenkins says the angel was a trough of low-pressure air in the northern Atlantic that pulled most storms away from the coast. Last year, there was a ridge of high pressure in that area. One big storm did strike the U.S. during the 2006 season. Hurricane Ernesto grazed Florida before landing in North Carolina and Virginia at the end of August. But by that time, Ernesto had been downgraded to a tropical storm. Jenkins says the hurricane season that wasn't shows just how tricky it is to predict the behavior of the elements.
JENKINS: The season was a good lesson in that even though sea temperatures may contribute to stronger hurricanes in the future maybe with global warming, you still got to consider these other factors.
HAMILTON: And forecasters are trying. They'll have another chance to get it right next year.
Jon Hamilton, NPR News.
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