Nasty 2003 hurricanes?

The 2003 hurricane season is likely to be a bad one for the East Coast.

BY TRAVIS DUNN | BALTIMORE | December 19, 2002

The 2003 hurricane season is likely to be a bad one for the East Coast, according to a report recently issued by Dr. William Gray, an atmospheric science professor at the University of Colorado, who has been issuing his famous hurricane predictions for 20 years.

Gray's latest report predicts an increase in the number and intensity of hurricanes for the Atlantic Basin, which includes the North Atlantic, the Caribbean Sea and the Gulf of Mexico.

Gray predicts 12 named storms (compared to an average of 9.6), eight hurricanes (average of 5.9) and three intense hurricanes (average of 2.3). Averages are computed from statistics from 1950 through 2000.

Gray's prediction also calls for a greater destructive capacity of storms and as well as an increased likelihood of landfall. He also disputes claims that the upsurge in hurricanes originating in the Atlantic Ocean is caused by global warming.

Gray issues an index called Hurricane Destruction Potential (HDP), a mathematical model used to determine the possible damage a hurricane might cause. Gray, who formulated the index himself in 1987, puts the HDP for 2003 at 100, 29 points above the average of 71.

Dr. Philip Klotzbach, one of Gray's colleagues at the University of Colorado, says that while the math behind the HDP may be a little confusing, its meaning is quite simple.

Klotzbach said HDP is calculated in the following manner: Scientists take recorded wind speeds during a hurricane every six hours. They square these figures, add up the numbers from all six-hour periods, then divide by the total number of six-hour periods. The result is the HDP.

The significance: as hurricane wind speed increases, damage increases at an exponential rate.

For example, a hurricane with an average wind speed of 120 mph would do four times the damage of a hurricane that had an average wind speed of 60 mph.

But the destructive potential of a possible hurricane is only meaningful if that hurricane actually hits something.

Chances are, Klotzbach said, these storms will strike land.

"The more active a season is," he said, "the more likely there is to be landfall."

The average landfall probability is 52 percent. For 2003, Gray and his colleagues say the overall likelihood is 68 percent.

And while the virulence of hurricane activity has been increasing steadily in the Atlantic Basin since 1995, Gray does not think that all this activity has any relation to global warming, as some have claimed.

"While hurricane activity in the Atlantic basin (the North Atlantic, the Caribbean and the Gulf of Mexico) may be on the rise, global hurricane activity has slightly decreased from 1995 through 2002," Gray wrote in a Nov. 22 report. "Various groups and individuals have suggested that the large upswing in Atlantic hurricane activity (since 1995) may be in some way related to the effects of increased man-made greenhouse gases such as carbon dioxide (CO2). There is no reasonable scientific way that such an interpretation of this recent upward shift in Atlantic hurricane activity can be made. The effects of anthropogenic greenhouse gas warming, even if a physically valid hypothesis, are a very slow and gradual process that, at best, might be expected to bring about small changes in global circulation over periods of 50 to 100 years. Hence, greenhouse gas-linked warming could not be responsible for the abrupt and dramatic upturn in hurricane activity which has occurred since 1994."

"Even if human-induced greenhouse gas increases were shown to be causing global temperature increases during the last 25 years," he wrote, "there is no way to relate such small global temperature changes to this high level of hurricane activity."

Gray also points out that hurricane activity sharply decreased in the Atlantic basin from 1970 through 1994. Proponents of the global warming theory, at least as it relates to hurricanes in the Atlantic, would have to reconcile this data with their hypothesis, he wrote.

Klotzbach said plenty of other factors can influence hurricane activity, and many of these are natural and cyclical.

One particular phenomenon Gray and his team have focused on is "thermal hailing circulation," a process in which saline deposits deep in the ocean are slowly brought up to the surface, sort of "like a conveyor belt."

When this process speeds up, Klotzbach said, there seems to be a corresponding increase in hurricane activity, as well as increased ocean surface temperature and decreased El Niņo activity. This cycle, he said, tends to run in periods of 25 to 40 years.

The Atlantic Basin, he said, just happens to be right in the middle of one of those cycles.

If Klotzbach, Gray and their research team are correct, then the Caribbean, the East Coast and the Gulf of Mexico will face plenty of bad hurricane weather in the future.

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