Study: More hurricanes could threaten Hawaii in coming decades

HONOLULU, May 6 (UPI) -- Hawaii, largely free from hurricanes in the recent past, could see a two- to three-fold rise in tropical cyclones by the end of this century, researchers say.

Scientists at the International Pacific Research Center of the University of Hawaii at Manoa said the increase would be driven by changes in large-scale moisture conditions, the flow patterns in the wind and in surface temperature patterns stemming from global warming.

"Computer models run with global warming scenarios generally project a decrease in tropical cyclones worldwide," lead author Hiroyuki Murakami said in the study published in the May 5 issue of Nature Climate Change. "This, though, may not be what will happen with local communities."

Most hurricanes that might threaten Hawaii now are born in the eastern Pacific, south of the Baja California Peninsula, but during the storms' long journey across the 3,000 miles to Hawaii they usually fizzle out due to dry conditions over the subtropical central Pacific and the wind shear from the westerly subtropical jet stream, the researchers said.

Even though fewer tropical cyclones will form in the eastern Pacific, Murakami said, the upper-level westerly subtropical jet would move poleward so that the mean steering flow becomes easterly.

Thus, storms from Baja California are much more likely to make it to Hawaii.

"Our finding that more tropical cyclones will approach Hawaii as Earth continues to warm is fairly robust because we ran our experiments with different model versions and under varying conditions," study co-author Bin Wang said.

"The yearly number we project, however, still remains very low," he said.