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Hurricane Dorian is moving slowly — but that only makes it more destructive

By Dan Conifer, Monday September 2, 2019 - 17:07 EST

Hurricane Dorian is crawling through The Bahamas.

The system is creeping westward at speeds as slow as 9 kilometres per hour.

You could run faster than this storm.

But do not let this fool you — this storm is the second-most powerful hurricane ever recorded in the Atlantic Ocean.

Why is this hurricane moving so slowly?

The speed at which a hurricane tracks is influenced by several factors, including the wind around it.

And outside Hurricane Dorian, there hasn't been much wind.

"The normal environmental flows that would be pushing it along are very weak at the moment," Canberra-based extreme weather expert Liz Ritchie-Tyo said.

What does this mean in terms of damage?

Generally, a slower hurricane simply has more time to inflict damage.

It has longer to tear buildings apart and drop rain, increasing the risk of flooding.

US-based meteorologist Philip Klotzbach said this hurricane was "very, very slow moving".

"These areas where the eye [of the storm] is going to be passing directly over are going to be experiencing heavy winds for … quite a few hours," he told the BBC.

What gives a hurricane its power?

Hurricanes, which are known in Australia as cyclones, begin as intense thunderstorms fuelled by warm ocean waters.

And then, under the right conditions, they start to rotate and intensify.

Dorian has come from a balmy part of the Atlantic Ocean.

"There are some really warm sea surface temperatures out there right now going out to the mid-Atlantic, 30-31 degrees Centigrade [Celsius]," Ms Ritchie-Tyo said.

"Dorian has taken full advantage of that.

"And it's really, really, really warm just before the Bahamas, and that's where it has intensified fairly quickly."

How fast are the winds within the hurricane?

Dorian is inching across the planet very slowly, but the rotating winds within the storm are some of the highest recorded for an Atlantic Ocean hurricane.

It made landfall in the Abaco Islands (in The Bahamas) packing winds of 295kph and gusts of more than 350kph.

That makes it the equal-second-strongest Atlantic hurricane on record, tying with Wilma in 2005, Gilbert in 1988, and one on Labor Day in 1935 (before the storms were given names).

The most powerful Atlantic hurricane, according to US authorities, was Allen in 1980, which had sustained winds of 306kph and killed more than 240 people across the Caribbean.

Do we know where Dorian is going?

Hurricane Dorian has already pounded the islands of Great Abaco and Grand Bahama as it moves west through The Bahamas.

Forecasters in the US predict the eye of the storm will change course and move north, tracking along the nation's east coast before returning to sea, but authorities warn that could easily change.

"There is a lot of uncertainty as to exactly when the storm will make the predicted turn to the north," Dr Klotzbach said.

At 1:00pm AEST on Monday the hurricane was only about 220 kilometres from the Florida coast.

The US National Hurricane Centre warned that even if the hurricane did not make landfall there would be torrential rains and devastating winds.

How many people live in the storm's path?

A spokesman for The Bahamas Government said it expected more than 70,000 of its residents to be affected.

And in the United States, more than one million people are covered by mandatory evacuations along the coastlines of Georgia and South Carolina (north of Florida).

In Florida, several counties have issued partial mandatory evacuation orders.

Other parts of the state have announced voluntary evacuations — including Palm Beach County, which is home to US President Donald Trump's Mar-a-Lago resort.


© ABC 2019

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