Hawaii May See An Increase In Tropical Cyclones
May 6, 2013

Number Of Hurricanes Reaching Hawaii Could Triple This Century

redOrbit Staff & Wire Reports - Your Universe Online

Hawaii could experience a two-to-three fold increase in the number of tropical cyclones by the year 2100, according to new research published Sunday in the online edition of Nature Climate Change.

Only two hurricanes have made landfall in the island state over the past three decades, but that is likely to change during the last quarter of this century, computer simulations developed by scientists at the University of Hawaii at Manoa´s International Pacific Research Center (IPRC) have revealed.

“Computer models run with global warming scenarios generally project a decrease in tropical cyclones worldwide. This, though, may not be what will happen with local communities,” lead author Hiroyuki Murakami, a postdoctoral fellow at the IPRC, said in a statement.

Murakami and Bin Wang, a climate expert that the university´s meteorology department, joined forces with Akio Kitoh of the Meteorological Research Institute (MRI) to determine whether or not climate change would lead to an increase in the frequency of tropical cyclones in the years ahead.

“The scientists compared in a state-of-the-art, high-resolution global climate model the recent history of tropical cyclones in the North Pacific with a future (2075—2099) scenario, under which greenhouse gas emissions continue to rise, resulting in temperatures about 2°C higher than today,” the university explained.

“In our study, we looked at all tropical cyclones, which range in intensity from tropical storms to full-blown category 5 hurricanes,” Murakami added. “From 1979 to 2003, both observational records and our model document that only every four years on average did a tropical cyclone come near Hawaii. Our projections for the end of this century show a two-to-three-fold increase for this region.”

According to the researchers, the primary reasons for this increase will be changes in large-scale moisture conditions, as well as wind flow and surface temperature pattern changes, all caused by warming temperatures stemming from global climate change.

Currently, most tropical cyclones posing a threat to Hawaii originate in the eastern Pacific, south of the Baja California Peninsula, Murakami and his colleagues explained. During the months of June, July, August, September, October and November, warm ocean temperatures combine with high moisture levels and weak vertical wind shear to create ideal conditions for hurricane formation. Those storms, however, typically dissipate before reaching Hawaii.

“Even though fewer tropical cyclones will form in the eastern Pacific in Murakami's future scenario, we can expect more of them to make their way to Hawaii,” the university said. “The upper-level westerly subtropical jet will move poleward so that the mean steering flow becomes easterly.”

“Thus, storms from Baja California are much more likely to make it to Hawaii,” they added. “Furthermore, since the climate models also project that the equatorial central Pacific will heat up, conditions may become more favorable for hurricane formation in the open ocean to the south or southeast of Hawaii.”