Two tropical storm systems’ proximity to each other might shield Carolinas from damage

NEW YORK — As a wet tropical system chugged north toward the Bahamas on Saturday, its threat to the Carolina coast might be determined by its unusual interaction — maybe even a rare dance — with another tropical system that could steer the mess out to sea.

A still unnamed and developing tropical depression — likely to become Imelda — is heading toward the Carolinas and is expected to become a hurricane with the potential to bring damaging heavy rains, especially if it stalls and keeps dumping rain for a while.

The storm could hit early next week, so residents of North and South Carolina need to be aware, especially of rain and flooding possibilities. But slight changes in its path and speed will determine how Hurricane Humberto, a big, bad storm already, might come to the rescue.

Humberto, which is farther east and threatening the U.S. territory of Puerto Rico, may get close enough to the future Imelda and start to interact. One possibility is that Humberto, which reached major hurricane status late Friday afternoon, could tug the smaller storm to the east. But if Humberto stays far enough away, it could allow Imelda to hover off the coast or make landfall.

“Even if we expect a slowdown and an eastward turn, exactly when that starts and where it happens will make a big difference in how close the center gets to the coastline,” said National Hurricane Center Director Michael Brennan.

As Imelda heads past the coast of Florida, Brennan said, there’s a tropical storm watch for parts of the state’s east coast. That means winds of at least 39 mph.

“There’s going to be a high risk of rip currents. People are not going to want to be out in the water,” Brennan said.

As the storm proceeds north, the Carolinas could face a significant flooding threat.

The storm is already producing a lot of moisture — officials said it is expected to dump as much as a foot of rain on Cuba. If instead of turning out to sea, the storm makes landfall or stalls just off the coast, there is a potential for dangerous amounts of rainfall and serious flooding, according to University of Miami hurricane researcher Brian McNoldy.

South Carolina Gov. Henry McMaster has declared a state of emergency for all of South Carolina and warned residents to play close attention to the storm.

As the systems advance, meteorologists are watching out for something incredibly rare that’s usually seen more in the Pacific: They could dance together, swirling around a spot in the middle. The phenomenon, called the Fujiwhara Effect for the Japanese scientist who discovered it, was first observed more than a century ago.

Two years ago, tropical storms Philippe and Rina did a little dance much farther away from the United States, McNoldy said.

Those were weaker storms with lower risks. That’s not the case here.

“This is more of a kind of high-impact, high-stakes forecast with potentially two hurricanes doing this right off the Southeast coast,” McNoldy said.

It’s something that typically happens when the storms are within 800 or 900 miles of each other.

“Not only would it be really neat to watch, but it would fling future Imelda out to sea,” he said.

Most interactions are likely to pull the younger, smaller system to the east and away from the coast, McNoldy said, adding that current models are showing that this possibility is growing more likely.

In a hurricane such as Humberto, the air rises up the middle and spreads out like a mushroom and then eventually sinks. It is that sinking air that may hamper Imelda-to-be, State University of New York at Albany atmospheric scientist Ryan Torn said.

This is so unusual that the National Oceanic and Atmospheric Administration is doing extra airplane missions to measure the atmospheric conditions between the two systems, Torn said.

This type of situation usually doesn’t happen because there is sort of a natural spacing out between developing storm systems that chug west off Africa, Torn said.

Hurricane Humberto, meanwhile, had maximum sustained winds of 145 mph Saturday, according to the Miami-based National Hurricane Center’s latest advisory. The storm was located about 365 miles northeast of the northern Leeward Islands. It was moving west at 8 mph.

Humberto could produce life-threatening surf and rip currents for the northern Leeward Islands, the Virgin Islands, Puerto Rico and Bermuda over the weekend, forecasters said.

The National Weather Service in Puerto Rico issued a small craft advisory, urging people to stay ashore and avoid unnecessary trips, with Saturday’s swells from Humberto expected to reach about 7 feet in Atlantic waters. It also advised residents to heed the beach warning flag system due to the high risk of rip currents.

Coastal and urban areas of Puerto Rico were also under an extreme heat warning.

In the Pacific, Hurricane Narda was churning about 1,025 miles west-southwest of the southern tip of Baja California and heading west-northwest at 12 mph. The Category 1 storm was expected to maintain its strength on Friday before weakening over the weekend.

Swells generated by Narda were affecting coastal Mexico and Baja California Sur, forecasters said. The swells that could bring life-threatening surf, and rip current conditions were expected to reach Southern California over the weekend.

Borenstein and Phillis write for the Associated Press and reported from New York and Washington, respectively. AP writers Freida Frisaro in Miami and Regina Garcia Cano in Caracas, Venezuela, contributed to this report.