Hurricane Dorian thrashed the Outer Banks of North Carolina Sept. 6 causing massive flooding while rescue efforts were underway. Hundreds were trapped in the islands at press time according to Gov. Ray Cooper as reported by The Associated Press.
The hurricane spawned 21 tornadoes across the Carolinas from September 4 to 5, according to the Storm Prediction Center, but the worst damage was in the Bahamas.
“We are in the midst of one of the greatest national crises in our country’s history,” Bahamas Prime Minister Hubert Minnis said in a news conference.
The death toll has reached 30 and the Prime Minister is expecting it to rise as rescue operations continue.
“It’s considered catastrophic,” said National Weather Service meteorologist Kurt Van Speybroeck who explained that winds of 167 m.p.h or higher would cause the total destruction of wood framed homes, which happened when Hurricane Dorian plowed across the Bahamas.
“Power outages will last possibly for weeks or months. Most of the area is considered uninhabitable,” Van Speybroeck said.
Dorian was classified as a Category 5 hurricane based on the Saffir-Simpson Wind Scale, a categorization method for hurricanes based on their sustained wind speed.
Satellite images show extensive damage to Grand Bahama Island where large portions of the island are underwater.
“One thing that [the Saffir-Simpson scale] does not address is also the amount of rainfall and flooding that is associated with major hurricanes,” said Van Speybroeck.
“Generally, the slower they move, like Harvey, you’ll see catastrophic flooding which will definitely make these impacts last more than a month or several months. If it’s fast moving, generally the rainfall is a little bit less but still you can have flooding that can last for several days in those areas,” he said.
Much of the destructive damage in the Bahamas was caused by the hurricane stalling.
Van Speybroeck said that it is considered rare for hurricanes to slow down and stall just like Dorian but can happen nonetheless. Hurricanes are considered very strong systems and the steering flow that determines where hurricanes go will always have some motion in them.
The system that influenced Dorian was the Bermuda High according to Van Speybroeck. The phenomenon is caused by a high pressure system in the Atlantic Ocean during the spring and summer months.
The Bermuda High is responsible for creating the paths of hurricanes. Van Speybroeck said that while Dorian was below the Bermuda High, it was pushed to the west. Later, when the storm was above the Bahamas, the slowed almost to a halt for 24 to 36 hours.
Although the storm was expected to hit Florida, that did not happen.
In very early projections, it was predicted to strike Florida as a Category 4 hurricane, prompting federal and local governments to take action and prepare for a possible disaster.
“As the model runs and picks up more and more of Dorian, we saw that it moved pretty significantly to the East because it never hit Hispaniola,” Van Speybroeck said.
“Because we were not flying the aircraft through the Bermuda High, the global models, which is what the hurricane center was using, had Dorian going west across the Bahamas and right into Florida,” she said.
He went on to say that further observation of Dorian with aircraft resulted in new forecasts and projections, changing the prediction maps.
While the hurricane was anticipated to hit Florida, it hit the Carolinas instead.
“Now there were some models that showed that early on, it’s kind of a rare solution so there were outliers and until we got really good models, we confirmed that this was going to happen.
The confidence in the forecast was not real high and you’re looking at a Category 5.” Van Speybroeck said.
Ultimately the hurricane spared Florida and came ashore along the Outer Banks of North Carolina.