Tropical Storms Flossie, Barry gain strength; East, Midwest brace for hail, flooding

Two tropical depressions gained strength off the coasts of Mexico and became tropical storms Sunday − and one could become a "significant hurricane" by Wednesday, the National Hurricane Center warned.

Neither storm −now named Barry and Flossie − was forecast to have much impact on the U.S., but parts of Mexico could face mudslides, 10 inches of rain and heavy winds, forecasters said.

Unrelated to the tropical storms, much of the U.S. Midwest and East faced rounds of severe thunderstorms packing strong winds and hail and raising flooding concerns Sunday and Monday. AccuWeather meteorologists said hot and humid air will clash with an advancing cool air boundary into early week causing thunderstorms to erupt, some of them severe.

As those storms push east on Monday, AccuWeather meteorologist Peyton Simmers warned that evening commutes Monday could be slowed in major cities such as New York City, Philadelphia and Washington, D.C.

Barry to drench parts of Mexico

Tropical Storm Barry, which formed in the Atlantic Basin, and Tropical Storm Flossie, in the Pacific Basin, were each driving winds of about 40 mph Sunday, just enought to gain tropical storm status.

"There are areas that could get 10 inches of rain" from Barry, AccuWeather lead hurricane expert Alex DaSilva told USA TODAY. "The main issues will be heavy rainfall and mudslides. Some areas such as Acapulco are still recovering from Hurrcane Erick."

Hurricane Erick, which was actually a Pacific Basin storm, made landfall on Mexico’s southern Pacific coast as a Category 3 storm on June 19. The storm brought destructive winds, heavy rains and widespread flooding to the states of Oaxaca and Guerrero. Homes, roads and infrastructure were destroyed or damaged, leaving thousands of people without shelter, food, water and electricity.

Barry was expected to rapidly weaken Sunday as it moves inland.

Flossie forming in Pacific, could become hurricane

In the Pacific Basin storm, Tropical Depression 6-E strengthened to Tropical Storm Flossie on Sunday. Flossie is moving toward the west-northwest a about 9 mph.

"Flossie is hanging off the western side of Mexico in a very favorable environment for intensification," DaSilva said. "Unlike the storm on the eastern side, Flossie could rapidly intensify and we do expect it to become a hurricane on Tuesday."

DaSilva said Flossie could top out as a Category 2 storm later Tuesday or Wednesday but is expected to remain offshore. Still, it is expected to get close enough to land to bring damaging winds to Mexico's coast.

Three to 6 inches of rain, with isolated areas of10 inches, were forecast across portions of the Mexican states of Oaxaca, Guerrero, Michoacán, Colima and Jalisco over the next few days, the hurricane center said. "Life-threatening" flooding and mudslides, especially in areas of steep terrain, were forecast.

Flossie, Barry get names from separate lists

The National Hurricane Center names storms in both basins but pulls from separate lists. The Pacific hurricane season actually starts May 15, while the Atlantic season began June 1.

Both basins are seeing more named storms than would be expected this early in their seasons, DaSilva said. Barry, as the second named storm for the Atlantic, is more than two weeks early. On average, a second storm is named on July 16.

"Flossie will be sixth named storm in the Pacific, where the average 6th named storm is Aug. 3. So we are two months ahead," DaSilva said. "This has been a very hot start to the season."

System could threaten Florida on Fourth of July

Later in the week, forecasters are watching for disturbances off the Southeast coast of the U.S. starting around the Fourth of July.

"The next thing to watch is what might happen July 4-7," DaSilva said.

He said a cold front is expected to stall in the northeastern Gulf of Mexico. Storms often form from stalled cold fronts, he said. DaSilva does not expect a hurricane, although the weather front could bring heavy rains to North Florida. But the threat remains several days out and it is possible it could result in only rip currents, he said.

How do hurricanes form?

Hurricanes are born in the tropics, above warm water. Clusters of thunderstorms can develop over the ocean when water temperatures exceed 80 degrees Fahrenheit. If conditions are right, the clusters swirl into a storm known as a tropical wave or tropical depression.

A tropical depression becomes a named tropical storm once its sustained wind speeds reaches 39 miles per hour. When its winds reach 74 mph, the storm officially becomes a hurricane.