In an update on Thursday, September 13, 2018, the Met Office said the centre of Tropical Storm Isaac passed through the northern Lesser Antilles at approximately 9:00 am Thursday and was passing over the eastern Caribbean Sea.
That storm, which has maximum winds of up to 255 km/h (equivalent to a Category 5 hurricane), was believed to be putting over four million people at risk.
"A life-threatening storm surge is highly likely along portions of the coastline of SC and North Carolina, and a Storm Surge Warning is in effect for a portion of this area", the National Hurricane Center said Wednesday.
Hurricane-force winds extend outward up to 45 miles from the center and tropical-storm-force winds extend outward up to 175 miles. The term typhoon is used for Pacific tropical cyclones north of the Equator west of the International Dateline.
No coastal watches or warnings were in effect as of Monday morning.
The tail end of Hurricane Helene is expected to reach Ireland early next week, bringing wet and windy weather.
All eyes are on Hurricane Florence and its path toward the Carolinas, but other hurricanes and tropical storms are brewing as well. They are also watching Tropical Storm Isaac, which is heading due west and expected to enter the Caribbean Sea on Thursday.
"Current indications are that (ex-) tropical storm Helene will approach Ireland's south coast during Tuesday".
Often the greatest threat from a hurricane is the storm surge. The storm is expected to slow down and possibly stall near or over the coast on Friday. So far Florence is moving very slowly - just 3-6 miles per hour.
President Donald Trump declared states of emergency for North and SC and Virginia, opening the way for federal aid.
According to NHC: "A Hurricane Watch means that hurricane conditions are possible within the watch area". Another system began forming near Hurricane Florence and was forecast at a 20 percent chance of formation over five days. Regardless of whether a system forms, they say heavy rain and gusty winds are likely along the Texas and Louisiana coast later this week.