NASA via AFP

A satellite-based image shows Hurricane Michael, right, and Hurricane Leslie, center, churning in the Atlantic Ocean on Thursday.

Updated at 5 p.m. ET -- Hurricane Michael became the first major Atlantic storm of 2012 on Thursday, but by late afternoon had weakened from Category 3 to Category 2. Michael was not expected to make landfall, but Hurricane Leslie was already creating waves in Bermuda.

Michael became a hurricane overnight and quickly grew to Category 3 strength with maximum sustained winds near 115 mph Thursday morning. By late afternoon, the winds had weakened to 110 mph, the National Hurricane Center stated, and further weakening was expected.

No coastal watches or warnings were in effect.

The seventh hurricane of the 2012 Atlantic season, Michael was expected to turn north-northwest with some gradual weakening possible by Friday.

Michael is "well removed from any land interests" and is "not a wave generator for the East Coast," Jonathan Erdman, a meteorologist for The Weather Channel, told NBC News.

Meanwhile, Leslie was basically stalled Thursday afternoon but still expected to pass near Bermuda on Sunday. 

Locals on Thursday were already moving boats out of the water.

"We still expect tropical storm force winds across the region on Saturday afternoon and storm force winds with hurricane force gusts (on Sunday) as the storm moves north and east," Jeff Torgerson of the Bermuda Weather Service told the Bermuda Sun.

"We are still expecting a significant storm," he added, "it’s best to hope for the best and prepare for the worst."

Storm Tracker: Detailed stats on NBCNews.com

A Category 1 hurricane, Leslie had maximum sustained winds of 75 mph, just a mile above hurricane status, and was about 430 miles south-southeast of Bermuda.

Leslie is expected to gradually strengthen over the next 48 hours and could become a Category 2 hurricane.

Current storm projections show Leslie tracking off the Eastern Seaboard to south of Nova Scotia, Canada, but not making landfall, Erdman said.

"Leslie will continue to be a generator of waves along the East Coast, with a rip current threat persisting through Saturday from Florida to New England," Erdman said.

Swells generated by Leslie will also impact Bermuda, Puerto Rico and the Virgin Islands "for the next few days," the hurricane center stated.

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Tropical Storm Leslie gained steam over the Atlantic Ocean and was upgraded to a Category 1 hurricane — the sixth Atlantic hurricane of the season — the National Hurricane Center said Wednesday.

“Maximum sustained winds are now 75 mph” with even higher gusts,  the NHC said in an alert. 

Leslie was about 465 miles southeast of Bermuda on Wednesday morning and was moving north at about 2 mph. "(Its) closest pass to Bermuda would be overnight Saturday night into early Sunday," said Jonathan Erdman, a meteorologist for The Weather Channel.

Current storm projections show Leslie tracking off the Eastern Seaboard to south of Nova Scotia, Canada, but not making landfall. "Leslie will continue to be a generator of waves along the East Coast, with a rip current threat persisting through Saturday from Florida to New England," Erdman said.

Leslie is expected to grow into a Category 2 hurricane by Saturday.

Related: Click here to see our storm tracker

Tropical Storm Michael, meanwhile, continues to churn farther east in the Atlantic. Storm projections show Michael growing into a Category 1 hurricane, perhaps by Wednesday evening, but it is not a threat to land. Michael is "well removed from any land interests," Erdman said, and is "not a wave generator for the East Coast."

The effects of Isaac, the storm that made landfall in Louisiana late last week as a hurricane, are still affecting parts of the United States.

U.S. regulators said about 50 percent of daily oil production and more than a quarter of daily natural gas output in the Gulf remains shut, Reuters reported.

Meanwhile, tar has washed ashore on some Louisiana beaches from Gulf waters churned by Isaac, according to The Associated Press.

Reuters and The Associated Press contributed to this report.

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As Tropical Storm Isaac makes its way over the Caribbean on Wednesday, forecasters expect it to turn into a hurricane later this week, sparking worries that it could threaten next week's Republican National Convention in Florida.

The storm is getting better organized as it moves west at 21 mph, with maximum sustained winds of 45 mph as of Wednesday morning. Forecasters predict Issac could turn into a hurricane by Friday. 

Related: Click here to track Isaac's path

Schools and government offices are closed across much of the Caribbean Wednesday as Isaac was positioned 140 miles east of the French Caribbean island of Guadeloupe.

In addition to much of the Caribbean, tropical storm warnings are also in effect for Puerto Rico and the U.S. and British Virgin Islands. Puerto Rico, Vieques, Culebra, the U.S. and British Virgin Islands and the south coast of the Dominican Republic are all under a hurricane watch.

Dominica Prime Minister Roosevelt Skerrit encouraged people to stay home from work on Wednesday, according to the AP.

"I want us all to be safe," he said. "I don't want lives to be lost. I have listened to the advice of the experts and so I am asking all to stay indoors." 

Puerto Rico is also bracing for the worst: Gov. Luis Fortuno activated the National Guard and declared a state of emergency, the AP reported.

By Wednesday evening, the storm's center is expected to be over the Leeward Islands, and it will move toward the Dominican Republic, Haiti and Cuba as a hurricane later this week, according to the AP.

AFP PHOTO / NASA GSFC GOES PROJECT

Tropical Storm Isaac strengthened on Wednesday and looked set to become a hurricane as it churned through the Caribbean.

National Hurricane Center computer models indicate that Isaac could move northwest and eventually reach Florida by Monday morning — the same day as the start of the Republican National Convention in Tampa.

Next week's GOP convention is expected to attract thousands of Republicans to nominate Mitt Romney for president and Paul Ryan for vice president. While it's too soon to tell whether Isaac will hit Tampa directly, senior hurricane specialist Lixion Avila, with the National Hurricane Center, told Reuters that Tampa is not out of harm's way.

"With the convention or without the convention, I can tell you this is August 22, hurricane season, and normally anywhere in Florida or the Gulf of Mexico we should monitor any system that forms," Avila said.

The Weather Channel's Bryan Norcross wrote a warning post on his Facebook page Wednesday: "Okay Florida ... it's time to wake up. Isaac is getting organized and the odds are increasing that it's going to be a problem ... a big enough problem that preparation is likely to be required."

Both Tampa and GOP officials say there are contingency plans in case the storm hits. FEMA has water and meals ready in the U.S. Virgin Islands.

In 2008, Hurricane Gustav churning toward New Orleans disrupted the Republican convention that was getting under way in Minneapolis. President George W. Bush Vice President Dick Cheney and Sen. Joe Lieberman canceled Sept. 1 speeches. Bush delivered a speech by satellite the next day. Aides to Sen. John McCain, the party’s presidential nominee, chartered a jet so Gulf Coast delegates could return home, according to media reports at the time. The storm largely spared New Orleans,  battered by Hurricane Katrina in 2005, but came ashore as a Category 2 hurricane and spawned damaging tornadoes.

Elsewhere, forecasters are also keeping an eye on Tropical Depression 10, which has formed over the eastern tropical Atlantic.

The Associated Press and Reuters contributed to this report.

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Forecasters are keeping a wary eye on Tropical Storm Isaac, which developed in the Atlantic Ocean on Tuesday and poses a threat to Florida during next week's Republican National Convention in Tampa.

National Hurricane Center computer models Tuesday predicted the storm would grow into a hurricane over the next few days. Some models had the storm striking Florida or passing close after moving across Cuba as early as Sunday.

The storm late Tuesday afternoon was about 500 miles east of Guadeloupe, the Hurricane Center reported. It packed sustained winds of 40 mph and was moving west at 17 mph.

NOAA via Getty Images

Tropical Storm Isaac moves westward in the Atlantic Ocean less than one week until the Republican National Convention in Tampa, Fla.

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A tropical storm warning was in effect for Martinique, Dominica, Guadeloupe and surrounding islands. A tropical storm watch was issued for the British and U.S. Virgin Islands and Puerto Rico.

Forecasters caution that long-range storm track predictions can be off by hundreds of miles. A hurricane hunter plane flew into the system Tuesday and found a small area of tropical-storm force winds associated with thunderstorms just outside the center of circulation, The Weather Channel reported.

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Thousands of Republicans will gather in Tampa next week to nominate Mitt Romney for president and Paul Ryan for vice president. GOP and Tampa officials say they have contingency plans in case a storm blows through.

This article include reporting by The Associated Press.

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