
© NASAIn the 1970s, the National Hurricane Center began using categories to describe how strong a hurricane's winds are and how much damage its gusts might be expected to cause
Scientists predict an increase in strong hurricanes with global warming. Will we have to revise the rating scale?As it moved toward to coast of Louisiana today, Hurricane Isaac was upgraded to a Category 1 on a scale that tops out at 5.
With wind speeds of about 75 miles per hour, Hurricane Isaac just barely earned the designation. Only at minimum speeds of 74 mph do winds become strong enough to cause significant damage, according to the National Hurricane Center.
Even though Category 5 storms, which sustain catastrophic gusts that blow at 157 mph or higher, are extremely rare, scientists predict an increase in strong hurricanes with global warming. That raises the question: Will we ever need to push the hurricane scale up to a 6?
Probably not, experts say. Even as warmer ocean temperatures provide more fuel for hurricanes, there are several factors that limit how powerful the storms can become.
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For now, about 200 mph is the highest that hurricane winds can theoretically get -- and only three land-falling storms have come close in the past century, said Mark DeMaria, a research meteorologist with the National Oceanic and Atmospheric Administration in Ft. Collins, Colo. With warming, according to some models, the upper boundry could reach 220 mph.
Comment: Hurricane Isaac hit New Orleans seven years to the day Hurricane Katrina levelled the city... is the Universe sending the US a message?