In the Atlantic, while Joyce is far out to sea and poses no immediate threat to land, 70-mph Helene is forecast to roar near the Azores on Saturday and Sunday, the National Hurricane Center said.
At 11 a.m., the storm was located about 520 miles east of Myrtle Beach, S.C., moving northwest at 15 mph with 130 sustained winds, forecasters said.
Tropical-storm-force winds extend outward up to 105 miles (165 km) from the centre.
Still closer to Africa than North America, Helen is predicted to head north in the Atlantic and not make landfall, the center says.More news: 9-year-old Aussie girl faces politicians ire over anthem protest
Advisory: Official information issued by warning centers describing all tropical cyclone watches and warnings in effect, along with details about location, intensity and movement.
Ahead of Helene is Hurricane Florence, a Category 4 storm that is projected to make landfall near the Carolinas later Thursday. Tropical Storm Isaac was expected to pass south of Puerto Rico, Hispaniola and Cuba.
A National Oceanic and Atmospheric Administration (NOAA) Hurricane Hunter aircraft is now en route to investigate the depression, according to the U.S. National Hurricane Center.
The National Hurricane Center is predicting the storm will produce "catastrophic flash flooding and significant river flooding".More news: Almost 40 fires and explosions erupt in MA
Emma Smith, meteorologist with the Exeter-based Met Office, said more details would emerge within the next day over what impact the storm might have. The storm has 45 miles per hour sustained winds with higher-speed gusts.
Florence is now 485 miles from Wilmington, North Carolina.
"Cloudiness and showers associated with a trough of low pressure over the south-central Gulf of Mexico have decreased since yesterday and the Air Force reconnaissance plane scheduled to investigate the system for today will likely be canceled", said the NHC on September 12. Mandatory evacuations have been issued for much of the SC and North Carolina coastline.
If the current atmospheric conditions persist - a layer of dry air and changing wind in the height - Isaac will weaken, becoming a tropical depression, and turning his course towards the south, without representing danger for Cuba. Another system began forming near Hurricane Florence and was forecast at a 20 percent chance of formation over five days.More news: Suspects in Skripal poisoning 'civilians, not criminals' - Putin