Hurricane Dorian: Deconstructing One of the Most Powerful Storms in History

Magicseaweed

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Updated 41d ago

Hurricane Dorian is one of the strongest hurricanes to have ever blitzed through the North Atlantic. It's tough to think that just two weeks ago, Dorian ripped apart the Bahamas as a Category 5, the highest it can be, leaving dozens of people dead and thousands without homes.

Relief efforts are currently under way. Waves for Water have been deployed to help out stricken communities and you can donate to the cause by going here.

Although parts of the US' east coast was graced with pumping waves (see here), many had to evacuate or reinforce their homes to brace for Dorian's full force. And while we can all enjoy looking at the session Dorian produced, it's important to understand what made this hurricane so powerful and track back its trajectory to the origin - uncovering exactly why Dorian was so deadly. The fact that it stalled for a few days in the Bahamas meant that islands were subjected to a sustained battering. But more on that later.

Related content: Hurricane Dorian Live

Dorian, exactly a week ago, after rifling through the Bahamas. Our North Atlantic swell chart can be found HERE.

Dorian, exactly a week ago, after rifling through the Bahamas. Our North Atlantic swell chart can be found HERE.

At MSW, we have comprehensive swell, wind, wave period and pressure charts, so you can follow the path of any energy in the water. You can view the charts by going HERE and it's what we use to trace a storm across the ocean.

Here, MSW forecaster Tony Butt breaks Dorian down: “With maximum sustained winds of 185mph and gusts of over 220mph, Dorian more than qualified as Category 5 on the Saffir-Simpson scale,” he said.

Dorian's trajectory outlined using MSW's wind charts.

Dorian's trajectory outlined using MSW's wind charts.

“Dorian was the second-strongest hurricane to make landfall in the Atlantic, close behind Hurricane Allen in 1980, which reached maximum sustained winds of 190 mph. Dorian’s central pressure dipped to an impressive 910 mb – not the lowest for hurricanes but lower than any mid-latitude depression.

“Dorian started off as a humble atmospheric disturbance on August 23 about half way between Cabo Verde and Venezuela, tracking westwards. It became Tropical Storm Dorian on August 25, just west of Barbados, and officially became a hurricane on August 28, just before narrowly missing Puerto Rico.

“Over the following few days Dorian moved steadily north-westwards and continued intensifying. By August 31, it was about 500 miles east of Palm Beach, Florida, now a Category-4 hurricane with maximum sustained winds of 140 mph.

“It then slowed right down, coming to an almost complete standstill for the next two days. It continued to strengthen, reaching Category 5 on September 1, as it made landfall on Elbow Cay in the Bahamas. The next two days were when Dorian caused utter devastation on Elbow, Grand Bahama and surrounding islands.”

NOAA's wind chart for Dorian as of last week.

NOAA's wind chart for Dorian as of last week.

Destruction is the apt word. It's been two weeks after Dorian struck and 2,500 people are still missing. The official death toll is around 50 people, but that figure is expected to rise. Government officials say the final death toll could be staggering.

Hundreds of people are currently being housed in shelters in the capital, Nassau, with emergency workers scrambled to build two tent cities around Marsh Harbour on Great Abaco island. Thousands of homes were destroyed and around 90cm of rain washed in, which caused severe flooding in some areas.

“It wasn’t till September 3 that Dorian started to gradually pick up speed and leave the Bahamas,” says Tony. “It tracked towards the northwest just off the coast of Florida, more or less weakening as it went, but still remaining a very intense hurricane for days afterwards.” Warnings were issued for Florida, but, luckily, Dorian moved onwards. But Dorian didn’t just sweep through with its reign of destruction; it came to an almost complete standstill, grinding away at the Bahamas for two full days

“It then kept accelerating, making landfall again at Cape Hatteras on September 6, before heading off towards Nova Scotia, where it arrived on the 8th, narrowly missing the capital, Halifax. At this stage the system still contained hurricane-force winds, but had lost its characteristics as a tropical storm,” Tony said.

“So why did Dorian become such as strong hurricane and why did it cause so much damage? Well, it was the combination of several factors, working together to maintain the system really strong but also keeping it in virtually the same place for over 48 hours.

“One of the main sources of fuel for a hurricane is the heat from the sea surface. In fact, the sea surface temperature (SST) must be at least 26°C before a hurricane can form. At the time of Dorian’s arrival in the area around the Bahamas, the SST was up around 29°C.

NOAA's Dorian timelapse.

“This coincided with a very small amount of shear in the atmosphere in that area at that time, which helped the system to intensify. Shear is the variation of windspeed and direction with height. Hurricanes don’t like shear because it impedes updraft (interferes with the air being sucked up the middle), and therefore weakens the system.

“But Dorian didn’t just sweep through with its reign of destruction; it came to an almost complete standstill, grinding away at the Bahamas for two full days. The trajectory and speed of a hurricane are dependent on larger-scale atmospheric systems that drive and steer it.

"The larger-scale systems near Dorian’s position on September 1 and 2 were too weak to push Dorian along. It was only after about two days that a trough of low pressure developed to the north and started to slingshot Dorian around its southern flank, accelerating it up the east coast, on towards Nova Scotia and beyond.”

It's some of the darkest days for residents of the Bahamas, their homes and lives devastated by a force they have no control of. Yet, some refugees have been barred from entering the US when seeking solid ground. After Dorian struck, some have been allowed to enter the country without visas but Brian Entin, a reporter for WSVN has said some Bahamians were kicked off a ferry when trying to evacuate from Freeport, Bahama, to Fort Lauderdale in Florida, due to not having the correct paper work.

Further, the US government has said it will not grant Temporary Protected Status for Bahamians already in the US. Now, there's been some misreporting of what this means - but the crux is that Bahamians in the US could still face deportation back to a stricken land. In the past, when natural disasters have hit, the US has granted this status to ensure people aren't shipped off to a volatile place.

Now, more than ever, the people of Bahama need your help. Waves for Water, as mentioned above, are on the ground, hit the link to help out. The Red Cross too. Several other charities have deployed and you can go HERE to donate.