Hurricane Florence is intensifying and expected to transform into a major hurricane as it barrels toward the southeastern USA coast, where forecasters expect a life-threatening storm surge, major flooding and damaging winds this week.
Tropical Storm Isaac, with maximum sustained winds of 70 miles per hour (110 kph), was expected to grow into a Category 1 hurricane on Sunday night but weaken again as it approached the Eastern Caribbean by mid-week, on a track taking it well south of Puerto Rico, the NHC said.
"Rapid strengthening is forecast, and Florence is forecast to become a major hurricane this morning, and is expected to remain an extremely unsafe major hurricane through Thursday", it said.
Swells generated by Florence already were impacting Bermuda and starting to reach the USA coast, with life-threatening surf and rip current conditions likely, according to the NHC. Such swells can lead to unsafe surf and rip currents, the NHC warned.
Tropical Storm Isaac, with maximum sustained winds of 65 mph (100 kph) and about 1,500 miles east of the Windward Islands, tracked south of Puerto Rico as it strengthened into a hurricane.
To become a hurricane, a storm must reach sustained winds of 74 miles per hour.
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Ships from Russia's Northern, Baltic and Black Sea Fleets would take part as would vessels from its Caspian Flotilla. The "Marshal Ustinov" missile cruiser would lead the drills.
"There is an increasing risk of coastal storm surge flooding and freshwater flooding from heavy prolonged rain when the hurricane approaches the US", said a NOAA tweet on Monday.
Isaac has become the fifth hurricane of the 2018 Atlantic season.
At 500 AM AST (0900 UTC), the center of Tropical Storm Helene was located near latitude 13.2 North, longitude 24.0 West. Helene is moving toward the west near 14 miles per hour (22 km/h), and this motion is expected to continue through today.
Isaac could become a hurricane on later today or by Monday morning.
"We are entering the peak of hurricane season and we know well the unpredictability and power of these storms", Cooper said.
Isaac may be a tropical storm or a hurricane near the Lesser Antilles late this week. The rapidly intensifying storm could strike a direct and unsafe blow anywhere from the Carolinas to the Mid-Atlantic region later this week, possibly as a fearsome category 4.
Adm. Christopher Grady said in a statement that the decision was based on Florence's current track, which indicates the area could see strong sustained winds and storm surges.
Forecasters urged residents from SC to the mid-Atlantic to get ready - and not just for a direct blow against the coast.