A powerful hurricane that formed in the Pacific Ocean this week was expected to continue strengthening over the coming days but will weaken before coming close to Hawaii, forecasters said.
The storm, Hurricane Calvin, which on Friday morning was a Category 2 storm with wind speeds of 105 miles per hour, is expected to begin weakening this weekend as it moves over colder waters and less hospitable atmospheric conditions. Though it is on track toward Hawaii, it is likely to weaken to a tropical depression by the time it reaches the state in the middle of next week.
“Calvin will likely impact the state beginning next Tuesday, but it is too early for details,” forecasters with the National Weather Service in Hawaii wrote on Friday.
Whether a hurricane forms in the Atlantic or the Pacific, it generally moves west, meaning Atlantic storms pose a greater threat to North America. If a storm forms in the Pacific close to land, it can bring damaging winds and rain before pushing out to sea.
Hawaii is in the central Pacific but is occasionally affected by storms that form to the east. It is unusual, however, for a named storm to make landfall in Hawaii, given that the state’s land area is small and divided among several islands. The last hurricane to make landfall in Hawaii was Iniki, in 1992. In 2020, Hurricane Douglas avoided a direct hit on the state but nevertheless produced damaging winds.
Hurricane season in the Eastern Pacific began on May 15, two weeks before the Atlantic season starts. Both seasons run until Nov. 30.
Complicating things in the Pacific this year is the development of El Niño, the intermittent, large-scale weather pattern that can have wide-ranging effects on weather around the world.
An El Niño reduces wind shear in the Pacific, which refers to changes in wind speed and direction. That instability normally helps prevent the formation of storms, so a reduction in wind shear increases the chances for storms. (In the Atlantic, El Niño has the opposite effect, increasing wind shear and thus reducing the chances for storm formation.)
There is solid consensus among scientists that hurricanes are becoming more powerful because of climate change. Although there might not be more named storms overall, the likelihood of major hurricanes is increasing.
Climate change is also affecting the amount of rain that storms can produce. In a warming world, the air can hold more moisture, which means a named storm can hold and produce more rainfall, like Hurricane Harvey did in Texas in 2017, when some areas received more than 40 inches of rain in less than 48 hours.
Researchers have also found that storms have slowed down over the past few decades.
When a storm slows down over water, it increases the amount of moisture the storm can absorb. When the storm slows over land, it increases the amount of rain that falls over a single location, like Hurricane Dorian in 2019, which slowed to a crawl over the northwestern Bahamas, resulting in a storm-total rainfall of 22.84 inches at Hope Town.
Research shows that climate change might have other impacts on storms as well, including storm surge, rapid intensification and a broader reach of tropical systems.