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7 Things to Know About Storm Surges

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Hurricane Katrina in the Gulf of Mexico in August 2005. Image credit: NOAA

 
When you think of the danger a hurricane poses to the unlucky people caught in its path, your first thought is probably the ferocious winds that crash ashore and tear up just about everything exposed to the elements. While the winds are destructive and the flying debris is a serious hazard to anyone caught in the way, the greatest and quietest killer in a tropical cyclone is its storm surge.

1. A SURGE IS A SUDDEN INUNDATION OF SEA WATER.

The strong winds of a landfalling tropical cyclone thrust it inland. The flooding that results from storm surges is only a few feet deep most of the time, but the worst surges—like those seen in Hurricane Katrina—can exceed 20 feet or higher. A storm surge comes up quickly and can push water miles inland in the most vulnerable spots during the strongest storms.

2. THEY'RE NOT CAUSED BY HURRICANES ALONE.

Hurricanes are most closely associated with storm surges, but they’re not the only storms that can push water inland. Tropical depressions and tropical storms can also inundate coastlines if their winds are strong enough. Powerful winter storms can also generate a life-threatening storm surge. A blizzard that hit the East Coast in January 2016 produced a storm surge in Cape May, New Jersey, that was slightly higher than the one recorded there during Hurricane Sandy a few years earlier. 

3. TRACK AND TIMING MATTER …

A diagram showing how a storm’s winds are influenced by its forward motion. Image credit: Chris Landsea/NHC

 
We tell people not to focus on the exact track of a tropical cyclone since the impacts can extend hundreds of miles from the center of the storm. But when it comes to a storm surge, track really does matter. The worst winds in a storm occur in the right-front quadrant of its eyewall, or the part of the storm that’s in front of the eye and to the right of its forward movement. This spot sees the strongest winds influenced by the forward motion of the storm, and it’s where the wind is able to push the most water with it.

Timing also determines how much flooding people at the coast will experience. Coastal flooding will be worse if a storm hits land at high tide since water will be a few feet higher. That couple of feet at high tide doesn’t seem like much, but it can mean the difference between a few roads washed out and a few neighborhoods inundated by water.

4. … BUT WIND MATTERS MORE.

The fury behind the surge is wind. The National Hurricane Center says that 95 percent of storm surge is driven by the wind—the other 5 percent is water that rises above sea level due to low air pressure at the center of the storm. A general (and obvious) rule of thumb is that a stronger storm will produce a more destructive storm surge, but surge also depends on other factors like a storm’s forward speed and the size of its wind field.

5. WIND IS WHY SANDY WAS SO DEVASTATING.

Hurricane Sandy’s wind field at landfall on October 29, 2012. Image credit: NHC

 
Even though Hurricane Sandy only had 80 mph winds when it made landfall in New Jersey on October 29, 2012, it was one of the most destructive storms to hit the United States in recorded history. The devastating storm surge that Sandy drove into coastal communities was the result of the immense size of the storm’s wind field.

When Sandy made landfall, the area covered by its tropical storm force winds (39–74 mph) covered more than 1100 miles from South Carolina to Maine. The enormous area covered by these strong winds made up for the storm’s relative lack of concentrated intensity, allowing it to push tremendous amounts of water into the coast.

Hurricane Katrina’s historic storm surge along the northern Gulf Coast in August 2005 was also driven by the sheer size of the storm. Katrina was a massive hurricane with scale-topping category 5 winds to boot. Katrina weakened by the time it reached the coast, but the size of the storm and its former strength still pushed enormous amounts of water into Louisiana and Mississippi.

6. CURVY COASTS MAKE A BAD SITUATION WORSE.

As if getting hit with a bad storm weren't bad enough, the very shape of the coastline itself will determine how much of an impact a storm surge will have on coastal communities. Shallow waters offshore and concave bays and inlets will exacerbate a storm surge and make the inundation deeper than it would have been otherwise.

7. LINGERING STORMS DO MORE DAMAGE.

After it made landfall in Florida and moved into the Atlantic Ocean, meteorologists were worried about tropical storm Hermine’s impacts along the Mid-Atlantic and New England coastlines because of how long they expected the storm to linger near land. Forecasts called for Hermine to meander off the coast of New Jersey at or near hurricane strength for four full days before beginning to dissipate. Thankfully, the worst-case scenarios didn’t come to pass, but the threat was real.

Even though Hermine wasn’t forecast to make landfall, the exceptionally long duration of the storm—powerful winds blowing inland for days at a time—threatened to generate a large storm surge along the coast. A slow-moving storm will cause more damage than one that moves through in a matter of hours. 

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Food
Thanks to a Wet Winter, New Zealand Faces a Potential Potato Chip Shortage
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iStock

New Zealand has plenty of unique and tasty snacks, but kiwis also love potato chips. The universal comfort food is in danger Down Under, however, as an unusually wet winter has devastated the island country’s tuber crops, according to BBC News.

Twenty percent of New Zealand’s annual potato crop was wiped out from a series of major storms and floods that ravaged the nation’s North and South Islands, The Guardian reports. In some regions, up to 30 percent of potato crops were affected, with the varieties used to make chips bearing the brunt of the damage.

Potato prices spiked as farmers struggled, but the crisis—now dubbed “chipocalypse” by media outlets—didn't really make the mainstream news until supermarket chain Pak’nSave posted announcements in potato chip aisles that warned customers of a salty snack shortage until the New Year.

Pak’nSave has since rescinded this explanation, claiming instead that they made an ordering error. However, other supermarket chains say they’re working directly with potato chip suppliers to avoid any potential shortfalls, and are aware that supplies might be limited for the foreseeable future.

New Zealand’s potato farming crisis extends far beyond the snack bars at rugby matches and vending machines. Last year’s potato crops either rotted or remained un-harvested, and the ground is still too wet to plant new ones. This hurts New Zealand’s economy: The nation is the world’s ninth-largest exporter of potatoes.

Plus, potatoes “are a food staple, and this is becoming a food security issue as the effects of climate change take their toll on our potato crop,” says Chris Claridge, the chief executive of industry group Potatoes New Zealand, according to The Guardian.

In the meantime, New Zealanders are preparing to hunker down for a few long months of potential potato peril—and according to some social media users, kale chips are not a suitable alternative. “Chipocalypse” indeed.

[h/t BBC News]

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Bess Lovejoy
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Weird
The Legend (and Truth) of the Voodoo Priestess Who Haunts a Louisiana Swamp
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Bess Lovejoy

The Manchac wetlands, about a half hour northwest of New Orleans, are thick with swamp ooze. In the summer the water is pea-green, covered in tiny leaves and crawling with insects that hide in the shadows of the ancient, ghost-gray cypress trees. The boaters who enter the swamps face two main threats, aside from sunstroke and dehydration: the alligators, who mostly lurk just out of view, and the broken logs that float through the muck, remnants of the days when the swamp was home to the now-abandoned logging town of Ruddock.

But some say that anyone entering the swamp should beware a more supernatural threat—the curse of local voodoo queen Julia Brown. Brown, sometimes also called Julie White or Julia Black, is described in local legend as a voodoo priestess who lived at the edge of the swamp and worked with residents of the town of Frenier. She was known for her charms and her curses, as well as for singing eerie songs with her guitar on her porch. One of the most memorable (and disturbing) went: "One day I’m going to die and take the whole town with me."

Back when Brown was alive at the turn of the 20th century, the towns of Ruddock, Frenier, and Napton were prosperous settlements clustered on the edge of Lake Pontchartrain, sustained by logging the centuries-old cypress trees and farming cabbages in the thick black soil. The railroad was the towns' lifeline, bringing groceries from New Orleans and hauling away the logs and cabbages as far as Chicago. They had no roads, no doctors, and no electricity, but had managed to carve out cohesive and self-reliant communities.

That all changed on September 29, 1915, when a massive hurricane swept in from the Caribbean. In Frenier, where Julia lived, the storm surge rose 13 feet, and the winds howled at 125 miles an hour. Many of the townsfolk sought refuge in the railroad depot, which collapsed and killed 25 people. Altogether, close to 300 people in Louisiana died, with almost 60 in Frenier and Ruddock alone. When the storm cleared on October 1, Frenier, Ruddock, and Napton had been entirely destroyed—homes flattened, buildings demolished, and miles of railway tracks washed away. One of the few survivors later described how he’d clung to an upturned cypress tree and shut his ears against the screams of those drowning in the swamp.

The hurricane seemed to come out of nowhere. But if you listen to the guides who take tourists into the Manchac swamp, the storm was the result of the wrath of Julia Brown. Brown, they say, laid a curse on the town because she felt taken for granted—a curse that came true when the storm swept through on the day of her funeral and killed everyone around. On certain tours, the guides take people past a run-down swamp graveyard marked "1915"—it’s a prop, but a good place to tell people that Brown’s ghost still haunts the swamp, as do the souls of those who perished in the hurricane. The legend of Julia Brown has become the area's most popular ghost story, spreading to paranormal shows and even Reddit, where some claim to have seen Brown cackling at the edge of the water.

After I visited the swamp earlier this year and heard Julia Brown's story, I got curious about separating fact from fiction. It turns out Julia Brown was a real person: Census records suggest she was born Julia Bernard in Louisiana around 1845, then married a laborer named Celestin Brown in 1880. About 20 years later, the federal government gave her husband a 40-acre homestead plot to farm, property that likely passed on to Julia after her husband’s death around 1914.

Official census and property records don’t make any mention of Brown’s voodoo work, but that's not especially surprising. A modern New Orleans voodoo priestess, Bloody Mary, told Mental Floss she has found references to a voodoo priestess or queen by the name of Brown who worked in New Orleans around the 1860s before moving out to Frenier. Mary notes that because the towns had no doctors, Brown likely served as the local healer (or traiteur, a folk healer in Louisiana tradition) and midwife, using whatever knowledge and materials she could find to care for local residents.

Brown’s song is documented, too. An oral history account from long-time area resident Helen Schlosser Burg records that "Aunt Julia Brown … always sat on her front porch and played her guitar and sang songs that she would make up. The words to one of the songs she sang said that one day, she would die and everything would die with her."

There’s even one newspaper account from 1915 that describes Brown's funeral on the day of the storm. In the words of the New Orleans Times-Picayune from October 2, 1915 (warning: offensive language ahead):

Many pranks were played by wind and tide. Negroes had gathered for miles around to attend the funeral of ‘Aunt’ Julia Brown, an old negress who was well known in that section, and was a big property owner. The funeral was scheduled … and ‘Aunt’ Julia had been placed in her casket and the casket in turn had been placed in the customary wooden box and sealed. At 4 o’clock, however, the storm had become so violent that the negroes left the house in a stampede, abandoning the corpse. The corpse was found Thursday and so was the wooden box, but the casket never has been found.

Bloody Mary, however, doesn’t think Brown laid any kind of curse on the town. "Voodoo isn’t as much about curses as it is about healing," she says. The locals she has spoken to remember Julia as a beloved local healer, not a revengeful type. In fact, Mary suggests that Julia’s song may have been more warning to the townsfolk than a curse against them. Perhaps Brown even tried to perform an anti-storm ritual and was unable to stop the hurricane before it was too late. Whatever she did, Mary says, it wasn’t out of malevolence. And if she’s still in the swamp, you have less to fear from her than from the alligators.

This story originally ran in 2016.

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