The current hurricane season, which runs through November, underscored Hawaii’s vulnerabilities to tropical cyclones, and a new University of Hawaii study predicts a warmer future could lead to stronger storms and could bring storms closer to the islands in El Nino years.
The study, which was lead by Nicole Murray, a former postdoctoral researcher in the UH School of Ocean and Earth Science and Technology, and atmospheric sciences professor Christina Karamperidou, examined Hawaii’s historical record and used computer models to predict potential cyclone activity in the middle and end of the century with different climate scenarios.
The model would use
climate information and generate synthetic storms that could form in the set conditions.
While the frequency of storms remains uncertain, Karamperidou said, the models did reflect a notion long-held in the scientific community: A warmer future could fuel stronger storms.
“We may not see more storms,” she said. “But the storms we will see may be stronger.”
The researchers also analyzed how El Nino and La Nina cycles may change over time, which yielded interesting results. El Nino, characterized by above-
average warming of the
Pacific, typically yields a busier hurricane season for the Central Pacific Basin while La Nina, characterized by abnormal cooling of the equatorial Pacific, typically yields a quieter season.
As temperatures get warmer, the difference between the two in terms of density of the storms gets smaller, but the cyclone paths impact different
locations.
El Nino years show more cyclones tracking south or southwest of the islands, Karamperidou said, which “is important because the most dangerous storms for us are the ones that come from the south.”
Hurricane Iniki in 1992, Hurricane Lane in 2018, and Hurricanes Lala and Lowell this year all formed or traveled from the south or southwest.
This year’s hurricane season — with four cyclones including Tropical Storm Moke and Hurricane Nolo — tracking south of the islands, could be a precursor of what’s to come.
“We always think about El Nino as a glimpse into the future in terms of the pattern of change in the tropical Pacific,” Karamperidou said. “A lot of these models, the projection that they have for the change in the tropical Pacific, is what we call and El Nino-like
pattern.”
Karamperidou said more future hurricane seasons similar to this year could be coming more often, especially with the difference between El Nino and La Nina getting smaller with time.
Predicting Hawaii’s future cyclone risk comes with challenges. The historical record is quite short in terms of observational data and the variability between hurricane seasons can make it more difficult to predict
patterns.
Rather than using the historical data as the sole way to predict future cyclones, the researchers also had synthetic cyclones appear when environmental conditions, such as high sea-surface temperatures and low vertical wind-shear, played out in the computer model. The models would generate thousands of plausible tracks for cyclones given the conditions so researchers could gather data on strength, tracks and other variables.
The study may be the first time synthetic tropical cyclone models have been used to predict Hawaii’s future cyclone hazard, Karamperidou said. The method has been used in other areas such as Texas, Florida and Mumbai, India.
In the absence of historical records, the synthetic cyclone analysis could be beneficial to help policymakers and residents alike prepare for future disasters, she said.
“We cannot (predict future cyclones) just by looking at the observational record alone,” Karamperidou said.
She emphasized that policymakers and residents should prepare for future hurricane seasons regardless of predictions. It only takes one hurricane to cause devastation, she said, and that could happen regardless of how El Nino or La Nina tips the scales of
probability.
While the frequency of cyclones in Hawaii is still uncertain over the next century under the models, Karamperidou said she’s confident the science and analysis ability will only get better and more accurate with time. Artificial intelligence, for example, has been extremely helpful in weather modeling as an emerging technology.
“We have a way forward to narrow down these uncertainties and have better predictions,” Karamperidou said.
The importance of showing how cyclone activity could change over the century can also help policymakers, power-generating companies and other entities make decisions on hardening and preparedness that can take a long time to procure.
“It’s good to know whether you have more of these events or less of these events,” she said. “It matters for infrastructure planning and preparedness, and emergency management planning takes time.”
At the same time, Karamperidou added: “By the nature of weather, we also need to understand that
we can never have the utmost certainty about something when it comes to a hurricane or weather, and that’s why we need to be prepared.”
