Florence may have been downgraded, but this is why it's still a life-threatening hurricane

On Thursday, Hurricane Florence was downgraded from a Category 3 to a Category 1 storm. However, meteorologists are warning that people in its path are still facing dangerous, life-threatening conditions.

Florence's sustained winds late Thursday were 150 km/h, with higher gusts. Those winds, though weaker, are behind the biggest threats: storm surges and widespread flooding.

Florence is a large storm packing hurricane-force winds that extend about 130 km outward from its centre; tropical storm-force winds extend even further, up to 315 km away.

As the storm — with those winds — nears shallow water along the coast, its forces water inland. North and South Carolina already faced flooding earlier this summer. The ground is saturated with water and unlikely able to withstand the heavy, persistent rains that are expected. This forces the water even further inland.

And then there's the major slowdown that's expected: as of late Thursday, Florence was moving at only about nine km/h. As it sits over a particular area longer, there is more rainfall. 

"For a meandering storm, the biggest concern — as we saw with Harvey — is the huge amount of rainfall," said Chris Landsea, chief of tropical analysis and forecast branch at the National Hurricane Center.

In August 2017, Harvey made landfall as a Category 4 and practically stalled over southern Texas, dropping record-breaking rain in many areas and causing widespread flooding.

And while some people may think that Florence doesn't possess the same punch Harvey did since it's only a Category 1 storm, there is a comparison: Sandy.

"This is a big storm, physically, very large. Kind of like Sandy," said George Kourounis, a storm-chaser from Toronto, who is in Wilmington, N.C. Hurricane Sandy formed in the Atlantic in 2012, hitting Jamaica and the Bahamas as a Category 1. Then it dropped to an extratropical cyclone — but with hurricane-force winds akin to a low Category 1 hurricane —  before making landfall in New Jersey. It caused 117 fatalities and cost the U.S. $17 billion.

"Hurricane Sandy did a tremendous amount of damage," Kourounis said. "Even though [Florence] has weakened, it is no less dangerous than it was yesterday."

Persistent rains and high winds will take their toll on structures.

"Think of it like a marathon," said Mark Robinson, from The Weather Network, also in Wilmington with Kourounis. "It's just going to be pounding and pounding and pounding for such a long period of time. Structures might be able to last a brief amount of time with 100 mile-per-hour [winds], but for a long period of time, that's when you're going to see things fall apart."

Kourounis and Robinson have seen their share of hurricanes, many of them together. This is Robinson's 18th; Kourounis, who was in Hurricane Katrina that devastated New Orleans in 2005, thinks this is either his 20th or 21st.

Though most residents of North and South Carolina and other areas in the hurricane's path have abided by the mandatory evacuation order, Kourounis jokes that the Waffle House is still open.

"They try to stay open as long as they can," Kourounis said. "FEMA actually uses the Waffle House index. "They monitor to see which Waffle Houses are still open and it helps them judge how badly a place is damaged. It's a thing."

Though the Waffle House may be open now, it's unlikely that will be the case in the days to come. 

North Carolina is home to millions of trees, Kourounis noted, and those trees are likely to come down, taking out power lines. The area will suffer far beyond the immediate effects expected.

Robinson noted that some of the forecasts are expecting rainfall of 800 to 1000 mm over a 30-hour period. Toronto saw widespread flooding twice this year when 50 mm of rain dropped in a few minutes. And this, he said, is like nothing Toronto has ever seen. And it's more than the Calgary floods of 2013.

What forecasters are keeping an eye on, in particular, is the forward motion of Florence. 

"We thought it was going to be easy [to forecast]," Kourounis said. "But it's been an intensity emotional rollercoaster."

With files from The Associated Press