Tropical Storm Kristy was expected to create life-threatening surf and rip currents of the coast of southern Baja California and southwest Mexico over the next few days, the National Hurricane Center warned Friday.

The NHC said winds had weakened to 50 mph by Friday afternoon but still posed a danger.

Tropical storm-force winds extended about 140 miles from the center.

“Swells generated by Kristy will affect portions of the coast of southwestern Mexico and southern Baja California during the next day or two,” the NHC notice said.

“These swells are likely to cause life-threatening surf and rip current conditions,” it added.

Meanwhile in the Atlantic, Tropical Storm Nadine had maximum sustained winds of 70 mph and was about 765 miles east-southeast of Bermuda, according to the NHC.

It was expected to turn north Friday and then head northeast toward the Azores Islands.

The NHC said little change in Nadine’s strength was expected but added “any strengthening would allow Nadine to become a hurricane.”

Storm-force winds extended about 230 miles from the center.

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Updated at 11:27 p.m. ET: As Isaac lashed south Florida on Sunday, the tropical storm threatened to make landfall later this week as a hurricane in New Orleans on the seventh anniversary of Hurricane Katrina’s near destruction of that historic city.

Although the worst seems to have passed in Florida – a relief to Republicans planning their national convention – officials in Key West ordered visitors and residents to remain indoors as the storm moved through the island chain.

“You’ve chosen to remain in the Keys during this storm and the only safe place for you to be is indoors,” said Monroe County Emergency Management Director Irene Toner. “Stay off roads and don’t go outside.”

300-mile stretch of Gulf Coast on alert after 'huge storm' Isaac drenches Florida

As of 11 p.m. ET, the storm had maximum sustained winds of 65 miles per hour, was about 75 miles west, southwest of Key West, moving west, northwest at 14 miles per hour, the National Hurricane Center in Miami, Fla. said.

Isaac caused weekend havoc in Cuba, where it downed trees and power lines. Before that, Isaac was blamed for seven deaths in Haiti.

Forecasters warned that Isaac could be upgraded to a Category 2 hurricane – capable of sustained winds of 96-100 mph – as it hits the northern Gulf Coast somewhere between Florida and Louisiana later this week.

The governors of Mississippi and Louisiana declared a state of emergency as officials prepared for Isaac.

Louisiana Gov. Bobby Jindal urged residents in low-lying areas of several southeastern parishes to voluntarily leave ahead of the storm. He said mandatory evacuations would likely be ordered on Monday. The governor also activated 4,000 National Guard troops and informed other states that Louisiana might need assistance if hit by Isaac.

"We’re all going to err on the side of being overprepared," Jindal said. He added that he may skip his speaking engagement at the Republican National Convention in Tampa, Fla., this week if his state is still threatened by the storm.

In the city of New Orleans, which was ravaged by Hurricane Katrina seven years ago, Mayor Mitch Landrieu also declared a state of emergency. "I'll remind everybody that we thought Katrina would be a wind and rain event," Landrieu said.

"Residents should be frightened because we have issued a State of Emergency," Mississippi Gov. Bryant said. "However, I urge individuals and families to finalize their personal preparedness efforts. Review your family communication plan, make sure your emergency supply kit is fully stocked and know where you will go if you need to evacuate."

The National Hurricane Center on Sunday evening discontinued a hurricane warning for the Florida Keys and west coast of Florida, but issued a hurricane warning hurricane for the northern Gulf of Mexico coast from the New Orleans area to the Florida Panhandle.

In South Florida, three people were killed in two separate crashes due to wet roads, reported NBC News affiliate NBCMiami.com. The first crash involved a head-on collision, which killed both drivers, and in the second, the car plunged into a canal and the driver drowned, officials said.

Some minor flooding and power outages were reported in the Florida Keys but with the worst seemingly over, South Florida officials were relieved as Isaac shifted west. "We prepared for the worst and for us it's a relief," Miami-Dade Mayor Carlos Gimenez  said, according to NBCMiami.com.

Related: Follow Isaac's path with our storm tracker
Related: Live updates and analysis from weather.com

Dr. Rick Knabb, director of the National Hurricane Center, said forecast models “can drive us nuts sometimes” but they play an important role for guidance.

“It’s still very uncertain where the center of Isaac will come ashore in its final landfall in the northern Gulf,” Knabb told the Weather Channel on Sunday, “and that can make all the difference as to who gets the strongest winds, who gets the strongest storm surge.

“Gradually, we’re seeing (Isaac’s) inner core develop. We’re certain it’s going to be a hurricane in the Gulf of Mexico,” Knabb said.

Cancellations and shutdowns
The Republican Party said it would recess its national convention in Tampa for a day out of safety concerns as the storm bore down. Republicans, who will formally nominate Mitt Romney as their presidential candidate for the November election, will briefly convene their four-day meeting on Monday, then recess until Tuesday. 

“When she storm passes and the sun comes out it’s going to be great to be in Tampa,” Tampa Mayor Bob Buckhorn said.

Related: Republicans effectively cancel first day of convention 

Gulf of Mexico oil operators braced for the first hurricane to affect the U.S. oil patch in 2012. Officials said the storm could shut down more than half of U.S. offshore oil output. Isaac's more westerly expected track brings it closer to the heart of the U.S. offshore oil patch, which produces about 23 percent of U.S. oil output and 7 percent of its natural gas output

Airlines are preparing for Isaac’s impact on Florida by waiving fees for changes and refunds for flights into and out of south Florida. Additionally, airlines on Sunday canceled most of south Florida operations.

Key West airports were closing Sunday night and most operations in and out of Miami and Fort Lauderdale were canceled until noon Monday, according to FlightAware.com. Airlines are not expecting long-term impact in Florida from the storm and should be operating normally by late Monday once airplanes, crew and staff are back in position. 

More than 740 flights to, from and within the United States were canceled Sunday in preparation for Isaac, with the bulk of the cancellations at Miami and Fort Lauderdale.

Meanwhile, the Sunday night performance of classic rock legends Lynyrd Skynyrd at Tampa’s American Action Network Pavilion at Liberty Plaza was canceled over safety concerns.

Old hat for locals
Key West locals followed time-worn storm preparedness rituals while awaiting the storm.

On Saturday, a steady line of cars moved north along the Overseas Highway, the only road linking the Florida Keys. Residents boarded up windows, laid down sandbags and shuttered businesses ahead of the approaching storm. Even Duval Street, Key West's storied main drag, was subdued for a weekend, though not enough to stop music from playing or drinks from being poured.

Slideshow: Isaac tracks toward Florida

Alan Diaz / AP

Tropical Storm Isaac rakes the Dominican Republic, Haiti and Cuba as it makes its way toward Florida.

Launch slideshow

"We'll just catch every place that's open," said Ted Lamarche, a 48-year-old pizzeria owner visiting Key West to celebrate his anniversary with his wife, Deanna. They walked along on Duval Street, where a smattering of people still wandered even as many storefronts were boarded up and tourists sported ponchos and yellow slickers.

"Category None!" one man shouted in a show of optimism.

Related: Weather Channel slideshow: The Wrath of Isaac

The Keys were bracing for storm surges of up to four feet, strong winds and the possibility of tornadoes. The island chain's two airports closed Saturday night, and volunteers and some residents began filing into shelters.

"This is a huge inconvenience," said Dale Shelton, a 57-year-old retiree in Key West who was staying in a shelter.

The Associated Press, Reuters and NBC's Isolde Raftery contributed to this report.

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• Video: Gulf Coast braces for Tropical Storm Isaac

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Updated at 6 p.m. ET: Tropical Storm Isaac was hugging the northern coastline of eastern Cuba on Saturday after claiming at least four lives in Haiti. Isaac should become a Category 1 hurricane on Sunday just as it nears the Florida Keys, the U.S. National Hurricane Center said, and then grow into an even stronger Category 2 storm with 100 mph winds.

Isaac "could be significantly stronger than currently forecast" once it enters the Gulf of Mexico, the center said in an advisory.

It will first sweep past southwest Florida and the Florida Keys, where "hurricane conditions are expected ... Sunday," it said in a separate update.

Republicans effectively cancel first day of convention

Isaac is a massive storm, with tropical storm-force winds extending 230 miles from the center. Key West International Airport was halting all flights at 7 p.m. Saturday until the storm had passed.

In Haiti, a woman and a child in the town of Souvenance were killed in the storm, a local official reported. A woman in the southern coastal city of Jacmel was crushed to death when a tree fell on her house, government officials said.

In the capital Port-au-Prince -- where some 350,000 people are still living in tents or shelters after the 2010 Haiti earthquake -- a girl, 10, was killed when a wall fell on her.

Power outages and flooding were reported as Isaac moved across the hilly and severely deforested Caribbean country.

"There's a lot of rain, a lot of wind," said Magdala Jean-Baptiste, who huddled with her frightened children in their home in the southern coastal city of Jacmel. "We haven't had any power since the storm started yesterday. We passed the night with no sleep." 

In neighboring Dominican Republic, Isaac felled power and phone lines and left at least a dozen towns cut off by flood waters. The most severe damage was reported along the south coast, including the capital Santo Domingo, where more than half the city was without power.

Cuba prepared by closing beaches and evacuating tourists in vulnerable areas, NBC's Mary Murray and The Weather Channel's Mike Seidel reported from Havana. Flights across Cuba were also suspended. 

In Baracoa, a city on Cuba's eastern side, high seas began topping the seawall Friday night, Radio Baracoa reported. 

Now with 60-mph winds, Isaac should exit Cuba on Sunday and then move south of the Florida Keys and into the Gulf.

Dieu Nalio Chery / AP

Residents wade through a flooded street in Port-au-Prince, Haiti, on Saturday.

Florida Gov. Rick Scott on Saturday declared a state of emergency to make sure local and state agencies would be ready. Republicans effectively canceled the first day of their national convention in Tampa, on Florida's central Gulf Coast, deciding to gavel it open on Monday, then immediately recess to some time on Tuesday.

Gulf of Mexico operators began shutting down offshore oil and gas rigs on Friday ahead of the storm. 

Follow Isaac's path with our storm tracker
Live updates and analysis from weather.com

Tampa's weather forecast includes rain and high winds Sunday night and into Monday, The Weather Channel reported. The winds could gust up to 60 mph.

Monday and Tuesday include a risk of tornadoes across south Florida. 

Officials were handing out sandbags to residents in the Tampa area, which often floods when heavy rainstorms hit. Sandbags also were being handed out in Homestead, 20 years after Hurricane Andrew devastated the community there. Otherwise, however, convention preparations were moving ahead as usual.

Isaac's exact path is still unclear, but the hurricane center said models suggest it will make landfall somewhere between the Florida Panhandle and New Orleans on Tuesday night.

The storm's anticipated path did shift closer to the Keys than previously forecast and emergency managers urged tourists to leave the islands if they could do so safely. A single road links the chain of islands to the Florida Peninsula. 

Reuters and The Associated Press contributed to this report.

Slideshow: Isaac tracks toward Florida

Walter Michot / AP

Tropical Storm Isaac rakes the Dominican Republic, Haiti and Cuba as it makes its way toward Florida, where Tampa will be hosting the Republican National Convention.

Launch slideshow

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Updated at 7:40 a.m. ET: Tropical Storm Isaac dumped heavy rains on Haiti on Saturday, threatening floods and mudslides in a country where hundreds of thousands of people remain homeless more than two years after a devastating earthquake.

Lashing rains and high winds were reported along parts of Haiti's southern coast and in the Haitian capital of Port-au-Prince, where more than 350,000 survivors of the 2010 earthquake are still living in fragile tent and tarpaulin camps.

Intermittent power outages affected the greater Port-au-Prince area in the early hours of Saturday as Isaac bore down on the impoverished Caribbean country.

At 5 a.m. ET, the U.S. National Hurricane Center issued a hurricane warning for the Florida Keys, including the Dry Tortugas, the west coast of Florida from Bonita Beach southward and Florida Bay.

It also issued a hurricane watch notice for Florida’s east coast from Golden Beach southward.

The NHC also said the Bahamas government had issued a hurricane watch for Andros Island.

The NHC's notice at 5 a.m. said Isaac had maximum sustained winds of 60 mph, down from 70 mph earlier Saturday, and was about 150 miles southeast of Guantanamo, Cuba.

'Life-threatening flash floods'
The Weather Channel reported that bands of heavy rain triggered flooding in Puerto Rico through Friday, even with Isaac's center well to the southwest. A bridge collapse and mudslide was reported early Friday. Power outages were also reported. The U.S. Virgin Islands were also affected.

The Weather Channel said heavy rainbands on the cyclone's eastern flank were expected to continue to hammer Haiti and the Dominican Republic.  

Follow Isaac's path with our storm tracker

Storm total rainfall of 8 to 12 inches is possible, with up to 20 inches locally, The Weather Channel said. Additionally, 4- to 8-inches of rainfall, with isolated incidents of 12 inches, was possible in Jamaica.  

"Life-threatening flash floods and mudslides will likely result from that amount of rain," it warned.

Aid workers prep Haiti's tent city residents for Isaac's onlsaught

Isaac's march across the Caribbean comes as U.S. Republicans prepare to gather in Tampa, on Florida's central Gulf Coast, for Monday's start of their national convention ahead of the November presidential election.

The convention is still expected to proceed as planned but Gulf of Mexico operators began shutting down offshore oil and gas rigs on Friday ahead of the storm.

But the biggest immediate concern was heavily deforested Haiti.

On Friday, the government and aid groups evacuated thousands of tent camp dwellers but many Haitians chose to remain in their flimsy, makeshift homes, apparently out of fear they will be robbed, said Bradley Mellicker, head of disaster management for the International Organization for Migration (IOM).

"There's a lot of people who are resisting because they are scared of losing what little they have now," Mellicker said.

Churches, schools are shelters
About 3,000 volunteers from the government's Civil Protection office were dispatched across Haiti, warning people about flood and landslide risks, and about 1,250 shelters -- schools, churches or other community buildings -- that have opened their doors to house people seeking refuge from the storm.

But Red Cross officials said the number of shelters could be grossly inadequate and Prime Minister Laurent Lamothe acknowledged Haiti had "limited means" to ensure public safety.

Red Cross and IOM representatives joined government officials in trying to evacuate 8,000 of the "most vulnerable people," including 2,500 sick and disabled, from 18 tent camps in low-lying coastal areas of Port-au-Prince.

Live updates and analysis from weather.com
Transcript of weather.com experts answering Isaac questions 

Many Haitians, most of whom scrape by on less than $1 per day, consider disaster an inevitable part of life in the poorest country in the Americas.

"We live under tents. If there's too much rain and wind, water comes in. There's nothing we can do," said Nicholas Absolouis, an unemployed 34-year-old mechanic at one camp for homeless people on the northern edge of the chaotic capital.

"There are still too many people living in the camps. There's a good chance that those might be destroyed with the passage of the cyclone," said France Hurtubise of the International Federation of Red Cross and Red Crescent Societies in Haiti.

Flooding could also help reignite a cholera epidemic, which has killed more than 7,500 people in Haiti since the disease first appeared in October 2010, foreign aid workers said.

Could hit New Orleans
On its current path, forecasters said Isaac would hit Cuba and the southern tip of Florida before making landfall anywhere from the Florida Panhandle in the northwestern part of the state to Alabama and as far west as New Orleans.

A tropical storm warning was issued for the entire coast of south Florida on Friday, and a hurricane warning also went into effect in the Florida Keys.

Isaac has drawn especially close scrutiny because of the Republican Party's convention, a four-day meeting during which former Massachusetts Governor Mitt Romney will receive the party's presidential nomination.

Party officials insist the convention will go ahead, even if they have to alter the schedule. But NHC meteorologist Rick Danielson said Tampa could potentially be hit by coastal flooding and driving winds or rain.

"There is still a full range of possible impacts on Tampa at this point," he said.

Danielson said it was very hard to project intensity before Isaac passes over mountainous Cuba on Saturday and Sunday and enters the Florida Straits. But the Florida Keys, the island chain off the southernmost part of the state, were definitely in harm's way.

Reuters contributed to this report.

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Nasa / Reuters

Tropical Storm Gordon, seen over the Atlantic Ocean in this NASA handout satellite image Thursday, became a hurricane Saturday.

Updated at 6:30 p.m. ET: Tropical Storm Helene made landfall off the Gulf of Mexico on Saturday and weakened into a tropical depression as it plowed up Mexico's east coast, the U.S. National Hurricane Center said.

The depression was about 65 miles west-northwest of Tampico and had maximum sustained winds of 30 miles per hour, the NHC said in its 4 p.m. CDT bulletin.

Tropical storm warnings were discontinued on the Mexican coast, although Helene still was expected to produce two to four inches of rain in the states of Veracruz and Tamaulipas.

Helene was predicted to continue weakening and dissipate within 48 hours, the NHC said.

There were no reports that Helene had affected the Gulf of Mexico's oil installations, which are built to resist much more powerful hurricanes.

Earlier, Portugal posted warnings for the central and eastern Azores islands as Tropical Storm Gordon moved eastward across the Atlantic and later turned into a hurricane.

The National Hurricane Center said Gordon had maximum sustained winds of 75 mph and was headed east at 18 mph.

In the northern part of Veracruz, a lush coastal state with hundreds of towns and villages sitting along streams and rivers that can swell dangerously in heavy rain many were evacuated as Ernesto approached last week, and flood damage made some 10,000 people homeless.

State of emergency
Mexico's government declared a state of emergency in more than 100 population centers in Veracruz and was providing them with emergency aid. The country's national weather service warned of intense rains and winds along the Veracruz and Tamaulipas coasts, with heavy rain, hail and lightning possible.

A storm surge could raise water levels by as much as 1 to 2 feet above normal along the immediate coast and to the north of where landfall is made.

Heavy rain was expected in the city of Tampico, an oil-refining center and important port in the southernmost part of Tamaulipas state. The Tampico metropolitan area has roughly 790,000 inhabitants, sits just above sea level and is surrounded by lakes and lagoons that are already full and could easily flood in the event of heavy rains.

Civil protection authorities in Veracruz issued a yellow alert, one level below the highest warning, for population centers in the north and center of the state, warning residents to familiarize themselves with the locations of emergency shelters, avoid crossing swollen streams and rivers, and keep listening to radio and TV for storm updates.

The Associated Press and Reuters contributed to this report.

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AFP - Getty Images, file

British female adventurer Sarah Outen sits in the narrow cabin of her rowing boat "Gulliver" in a suburb of Tokyo, April 11, 2012, before heading across the Pacific to Canada.

Updated at 5:50 p.m. ET: A 27-year-old woman trying to row solo across the Pacific Ocean was “holding on” hoping for rescue after her 23-foot boat was hit by a tropical storm.

The storm, named Mawar, rolled Sarah Outen’s boat Gulliver several times, damaging the vessel, according to her blog. A Japanese Coast Guard plane was staying overhead “to keep an eye on Sarah” while a Coast Guard boat went to pick her up. It was expected to arrive Friday.

As the storm hit Wednesday, Outen, from Rutland, England, said on her Twitter account that she had “written ‘SMILE’ on one hand and ‘BREATHE’ on the other. Both will help when I am scared in the storm.”

At about 9:50 a.m. ET Thursday, she wrote her cabin was soaked and she was now “wrapped in Union Jack [British flag] in place of soggy” sleeping bag and “holding on.”

On her blog, London 2 London via the World, her support team wrote they had spoken to her and she was “safe and doing well.”

Outen’s Pacific row was just one leg of a planned round-the-world journey by bicycle, rowing boat, and kayak that started on April 1 last year.

Fellow British Rower Charlie Martell was also awaiting rescue in his boat Blossom, the London 2 London website said in an update Thursday. Martell is approximately 280 miles northeast of Outen. The Japanese Coast Guard was keeping an eye on him, too.

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