Hurricane Adrian Churns Off the Coast of Mexico in the Eastern Pacific

Hurricane Adrian continued to move westward off the coast of Mexico on Thursday, a day after it rapidly intensified to become the first hurricane in the eastern Pacific region this year, the National Hurricane Center said.

The storm was moving across the Pacific and away from Mexico’s west coast on Thursday, the Hurricane Center said. It had maximum sustained winds of 90 miles per hour, above the threshold of 74 m.p.h. that makes a storm a hurricane. Tropical disturbances receive a name when they pack sustained winds of at least 39 m.p.h.

As of Thursday afternoon, there were no coastal watches or warnings in effect for Adrian, according to the National Weather Service, though the Hurricane Center warned that swells generated by Adrian were affecting parts of the western Mexico and Baja California coasts. “These swells are likely to cause life-threatening surf and rip current conditions,” the center said.

A separate weather system, Tropical Storm Beatriz, formed farther south in the Pacific on Thursday afternoon, the Hurricane Center said. As of Thursday night, that system was about 100 miles southwest of Acapulco, Mexico, with maximum sustained winds of 40 miles per hour and was expected to “rapidly intensify,” becoming a hurricane by Friday, the Hurricane Center said. Some tropical warnings and watches related to that storm system were in effect for a portion of the country’s southwestern coast.

Heavy rains were being reported on the shores of Oaxaca and Guerrero, and up to seven inches of rain was expected across southern Mexico where there was a possibility of flash flooding.

Maria Torres, a meteorologist with the National Hurricane Center in Miami, said on Wednesday that Adrian would maintain the same general direction through Thursday and that it was expected to make a turn to the west-northwest on Friday. The hurricane did not appear to represent an immediate threat to land and would remain over open waters, she said.

But Ms. Torres said that people living along the coastal areas of Mexico should monitor the storm and watch for updates from their local meteorology offices, “because it can create rip currents and hazardous beach conditions.”

When a tropical storm forms in either the Atlantic Ocean or the Pacific Ocean, it generally moves west, meaning that Atlantic storms usually pose a greater threat to North America. When a storm forms close to land in the Pacific, it can bring damaging winds and rain before moving out to sea.

However, an air mass can sometimes block a storm, driving it north or northeast toward the Baja California peninsula and other parts of the west coast of Mexico. Occasionally, a storm can move farther north, as was the case last year with the post-tropical cyclone Kay, which brought damaging wind and intense rain to Southern California.

Some Pacific storms even move across U.S. land; in 1997, Hurricane Nora made landfall in Baja California before moving inland and reaching Arizona as a tropical storm.

Hurricane season in the eastern Pacific began on May 15, two weeks before the Atlantic season started. Both seasons run until Nov. 30.

Complicating things in the Pacific this year is the likely development of El Niño, the weather pattern that can have wide-ranging effects around the world.

In the Pacific Ocean, El Niño reduces the changes in wind speed and direction that are known as wind shear. The instability of wind shear normally helps prevent the formation of storms, so a reduction increases the chances for storms. (In the Atlantic Ocean, El Niño has the opposite effect.)

On average, the eastern Pacific hurricane season generates 15 named storms; eight typically reach hurricane strength, and four become major hurricanes with winds that reach 111 m.p.h. In the Central Pacific, four to five named storms develop or move across the basin each year.

There is 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 that a named storm can bring more rainfall, as 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. In 2019, Hurricane Dorian slowed to a crawl over the northwestern Bahamas, resulting in a storm-total rainfall of 22.84 inches in 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.

Livia Albeck-Ripka, Eduardo Medina, Claire Moses and Mike Ives contributed reporting.