Meanwhile, Hurricane Florence was 580 miles south, south east of Bermuda with winds of 115 mph and strengthening into a major storm.
The storm is located 725 miles west of the southernmost Cabo Verde Islands and about 1,515 miles south-southwest of the Azores, moving northwest at 12 mph.
Hurricane Florence is now a category 4 hurricane.
FEMA administrator Brock Long is warning that the hurricane will be a "devastating event" and urging Americans to evacuate if they've been asked to leave their homes.
"I don't think many of us have ever been through a Category 4".
At 11 a.m., Tropical Storm Isaac, carrying maximum sustained winds near 70 miles per hour, was located about 775 miles east of the Lesser Antilles and was moving towards the west at 16 miles per hour.
"The bottom line is that there is increasing confidence that Florence will be a large and extremely risky hurricane, regardless of its exact intensity", Blake said. Forecasters also warned of a rising threat of life-threatening storm surge, along with the damaging winds.
Helene stays in Atlantic and turns to the north where it will weaken over colder waters.
It appears the storm is mostly likely to make landfall in North or SC by the end of the week, but it could still shift, and states in the Mid-Atlantic and Southeast are being warned to brace for potentially historic storm effects.
North Carolina Governor Roy Cooper told a news conference his state was in "the bull's eye".
Considering this southern state on the east coast lies super close to the stretch of the Atlantic that creates these hurricanes, they've seen quite a bit more of these disasters than their northern counterparts.
Winds of tropical storm force could reach Puerto Rico Thursday evening.
Unlike the Atlantic and eastern Pacific basins, tropical storm season never ends in the western Pacific. Hurricane Isaac, churning in the mid-Atlantic Ocean with wind speeds of around 75 miles per hour, is following closely behind Florence.
Behind Hurricane Florence, Hurricane Isaac and Hurricane Helene are both swirling in the Atlantic.
"Hurricane #Florence this morning as seen from @Space_Station", Arnold tweeted on Monday. Little change in strength is forecast during the next few days, but Isaac is forecast to be at or near hurricane strength as it approaches the Lesser Antilles.