A powerful hurricane that formed in the Pacific Ocean this week weakened on Sunday to a tropical storm and is expected to continue to lose strength before coming close to Hawaii, forecasters said.
Tropical Storm Calvin had maximum sustained wind speeds of 70 miles per hour on Sunday morning, forecasters said, making it a tropical storm. It dropped from a Category 3 hurricane on Friday night to a Category 2 on Saturday.
The storm is moving west-northwest at 16 m.p.h. toward Hawaii and is expected to move in that same direction over the next several days, the National Hurricane Center and the Central Pacific Hurricane Center said.
It was about 1,355 miles from Hilo on the northeastern coast of the Big Island on Sunday morning.
There were no coastal watches or warnings in effect as of Sunday morning. A tropical storm watch could be issued for portions of the islands late on Sunday, forecasters said.
Though it is on track toward Hawaii, it is likely to be downgraded to a tropical depression by the time it reaches the state in the middle of the week.
Calvin is expected to approach Hawaii on Tuesday and pass near or over the Big Island early on Wednesday, forecasters said.
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.
Christine Hauser, Rebecca Carballo and Lauren McCarthy contributed reporting.
