HONOLULU (KHON2) — Hurricane season has a variety of meanings for various people. But one thing that everyone understands is the destruction that can come from a particularly destructive storm.

These storms are some of the most destructive natural disasters in the world. They bring with them torrential rains, flooding, destructive winds and coastal storm surges.

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Researchers at the University of Hawaiʻi at Mānoa have found that since the 1980s, category 4 and 5 storms have been arriving in populated areas three to four days earlier with each passing decade. Scientists believe the consequences of climate change are to blame.

“When intense tropical cyclones occur earlier than usual, they cause unexpected problems for communities,” said Pao-Shin Chu, atmospheric sciences professor in the UH Mānoa School of Ocean and Earth Science and Technology and Hawai‘i State Climatologist.

The team’s research has been published in Nature.

“Moreover, the earlier advance of these storms will overlap with other weather systems, for example local thunderstorms or seasonal summer monsoon rainfall, and can produce compounding extreme events and strain the emergency response,” added Chu.

As oceans warm and glaciers melt, many characteristics of severe weather are evolving. This includes hurricanes. But little has been done to study and understand the seasonal cycles that are being impacted by global warming.

So, the research team utilized satellite data to track historical tropical cyclone paths, NOAA rainfall records and various statistical data associated with climate research. They found that there has been a significant shift of these intense tropical cyclones from autumn to summer months since the 1980s in most tropical ocean areas.

“It was surprising to consistently see earlier arrivals when we independently assessed satellite data and conventional ground-based observations of intense tropical cyclones,” said Chu.

The North Pacific off the coast of Mexico proved to be a particularly fertile region for the research where they observed the effects. This area is where most hurricanes that come near Hawai‘i form.

They also examined the western North Pacific, the South Pacific, the Gulf of Mexico and the Atlantic coast of Florida and the Caribbean.  

“Given the seasonal advance of intense tropical cyclones, as shown in this study, the potential for simultaneous occurrence with other high-impact weather events should be a serious concern for the society,” said Chu.

Hurricane Harvey, which hit Texas and Louisiana, from August 2017 was a category 4 storm; and Hurricane Lane, which hit Hawaiʻi, from 2018 was a category 5 storm. Both were particularly destructive with extreme amounts of rain and a number of deaths.

“Understanding potential changes in hurricane activity in response to global warming is important for disaster prevention, resource management and community preparedness,” said Chu.

The team also used simulations from high-resolution climate models, which showed them that warmer oceanic conditions were developing earlier leading to favorable conditions for an earlier onset of intense tropical cyclones. And greenhouse gasses were found to be a major contributing factor.

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“In a future with high carbon dioxide emissions, the earlier shifting trend is projected to be amplified,” concluded Chu.