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Science

More Hurricanes Expected Over Hawaii By End Of Century

Hawaii does not have to suffer the impact of hurricanes often — with only two making landfall in the past 30 years — however this may be set to change in a warming world, according to new research headed by a team of scientists at the International Pacific Research Center, University of Hawaii at Manoa.

Hawaii is just a bit too far along the Pacific hurricane path to be greatly affected by the massive storms, as they tend to fizzle out by the time they have travelled that far and encountered the dry conditions over the subtropical central Pacific combined with the wind shear from the westerly subtropical jet.

Appearing in the May 5 online issue of the journal Nature Climate Change, the research shows that Hawaii could see a two-to-three-fold increase in tropical cyclones by the last quarter of the century.

“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,” says lead author Hiroyuki Murakami.

Murakami and climate expert Bin Wang at the Meteorology Department of the University of Hawaii at Manoa, joined forces with Akio Kitoh at the Meteorological Research Institute and the University of Tsukuba in Japan to compare the recent history of tropical cyclones in the North Pacific with a future scenario with temperatures about 2°C higher than today.

“In our study, we looked at all tropical cyclones, which range in intensity from tropical storms to full-blown category 5 hurricanes,” explains Murakami. “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.”

This image shows the projected change in number of tropical cyclones per year by the last quarter of this century. The green stippling indicates statistical significance at the 99 percent confidence level.  Image Credit: Hiroyuki Murakami, Nature Climate Change
This image shows the projected change in number of tropical cyclones per year by the last quarter of this century. The green stippling indicates statistical significance at the 99 percent confidence level.
Image Credit: Hiroyuki Murakami, Nature Climate Change

According to the researchers, the three main factors responsible for increasing the number of hurricanes over Hawaii are the large-scale moisture conditions, the flow pattern in the wind, and the surface temperature patterns resulting from global warming.

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. 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.

“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,” added co-author Wang. “The yearly number we project, however, still remains very low.”




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