Friday, November 30, 2007

Atlantic hurricane season ends

Disaster News Network: The 2007 Atlantic hurricane season officially comes to a close today, and while residents in the U.S. are breathing a sigh of relief that they escaped what had been predicted to be a highly active storm season, people in other countries weren't as lucky. The hurricane season - which runs from June 1 to Nov. 30 - ends with 14 named storms, of which six were hurricanes. Two of them – Dean and Felix - were the first two Category 5 Atlantic storms to make landfall in the same season since record-keeping began.

As the season ends, questions were being raised about the accuracy of pre-season forecasts, which proved to be generally wrong for the second year in a row.

…"The 2007 Atlantic hurricane season actually produced quite a bit of activity," said Gerry Bell, lead seasonal hurricane forecaster with NOAA. "For the activity as a whole, the season was near normal. But the intensity and duration of the hurricanes was the big issue. The intensity and duration of the hurricanes was less than predicted. That was the big issue from a forecasting prospective."

Bell said storm predictions were based on oceanic and atmospheric conditions that historically have produced very active hurricane seasons. The current active hurricane era, which began in 1995, is far from over, he warned. Active eras can last from 25 to 40 years. "We had less than expected activity but the conditions associated with this ongoing active hurricane era are still in place," he said. "I don’t see any basis for thinking that somehow the current active era has ended or is weakening. We are still in an active hurricane era. "Diligence and preparation are still absolutely called for," he added. "People should not become complacent."

Bell said it appears that the main factor skewing the hurricane predictions was the effect of La Nina on the Atlantic. "La Nina impacts over the Atlantic were not as strong as expected and we're still investigating why," he said. "The question we're looking at is what other climate factors were in place that kind of swamped the La Nina impact over the Atlantic and as a result we wound up with stronger upper level winds, stronger wind shear, and as a result less intense, weaker and shorter-lived hurricanes. "That appears to be the main issue why the activity was over-predicted as a whole," he said.

Klotzbach cited wind shear and cooler Atlantic waters as reasons why the season was not as active as predicted. "The reasons for this year's average season are challenging to explain," he said. "It is impossible to understand how all these processes interact with each other to 100 percent certainty. Continued research should help us better understand these complicated atmospheric/oceanic interactions."

…Hill of Florida Interfaith Networking in Disaster said she believed that even though residents in her state dodged the bullet this season, they shouldn't relax too much. "In Florida, I think it's a true statement that 'it's not if but when,'" she said. "This year wasn't the year."

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