The potentially catastrophic Hurricane Florence is barrelling towards the US southern coastline at the same time that Hurricane Olivia threatens Hawaii with heavy flooding.

The two major storms simultaneously churning in the Atlantic and Pacific oceans have created a unique phenomena during a historic hurricane season, according to analysts.

Multiple states, including Maryland and Virginia, as well as North and South Carolina, have declared states of emergency as Florence is expected to make landfall on Thursday. Meanwhile, Hawaii may face up to 15 inches of rain from Olivia, just two weeks after Hurricane Lane caused extensive flooding throughout the region.

Agencies monitoring storms in both oceans have warned of potentially extensive damage and flooding to impacted areas.

In a statement on Sunday, the Central Pacific Hurricane Centre said “Damaging tropical storm force winds may begin in some parts of the islands as early as Tuesday afternoon and evening”.

Meanwhile, the National Hurricane Centre announced “a rapid phase of intensification” had begun over the weekend with Florence expected to reach Virginia on Thursday.

The state’s governor, Ralph Northam, has warned of possible flooding and high winds, urging residents to prepare for potential evacuations.

“I am declaring a state of emergency so that we can begin to prepare state assets, and I encourage Virginians to monitor forecasts and make their own preparations now,” Mr Northam said ahead of the storm’s arrival.

South Carolina Governor Henry McMaster also said “We are preparing for the worst and of course hoping for the best” after both Carolinas declared states of emergency.

Hurricane Lane wreaks havoc on Hawaii's Big Island

Maryland’s Governor Larry Hogan declared a state of emergency on Monday afternoon, telling reporters, “We are preparing for the potential of historic, catastrophic and life-threatening flooding in Maryland.”

Large sea swells and intense currents have already formed along North Carolina’s coastline, with Governor Roy Cooper telling residents in a statement, “Everyone in North Carolina needs to keep a close eye on Florence and take steps to get ready for impact later this week”.

“I urge the public to review your emergency plans and gather your supplies now,” he continued.

The hurricane has sustained winds of 70 mph, resulting in potentially “life-threatening” conditions along the coast, according to the National Hurricane Centre, which said in a previous announcement that “the risk of direct impacts continues to increase.”

It remains unclear exactly what impact either storm may have in the days ahead. Some analysis has indicated Hurricane Florence could slow or stall across the mid-Atlantic, resulting in heavy rain.

“There is an increasing risk of two life-threatening impacts from Florence: storm surge at the coast and freshwater flooding from a prolonged heavy rainfall event inland,” the agency wrote in its statement over the weekend.

Storms churning throughout the northeast Pacific ocean have triggered the most “accumulated cyclone energy” on record, according to Phil Klotzbach, who spoke to NBC News about the ongoing storms.

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“The thing that’s interesting now is the Pacific is still active, but the Atlantic is very active, which isn’t normal,” he said. “I’m surprised to see the Pacific and Atlantic active at the same time.”