Hurricane Hermine generated a widespread storm surge along Florida's West Coast, north of the Tampa-St. Petersburg area. Water levels were particularly high to the east and south of Apalachee Bay, in areas like Cedar Key. The graph below plots Hermine's water level within a broader context of storm surge events at Cedar Key. The water levelMore
If you live on the East Coast, you could be in for a soggy, windy, wavy long weekend thanks to Tropical Storm Hermine. Parts of the Mid-Atlantic could see a top-10 flood event from the storm as it heads up the coast and then parks in the region for days on end.
Hermine has already caused the fifth-highest water level in Cedar Key, Fla., and left nearly 300,000 people in the dark when it made landfall as a hurricane on Thursday after a record-setting 3,966 days without a hurricane in the state. It’s since been downgraded to a tropical storm and will bring torrential rain and gust winds to southeast Georgia on Friday before setting its sites on the rest of the East Coast this weekend.
Dangerous rip currents and erosion are huge concerns along the coast. That alone would be bad enough for residents, but Labor Day is also one of the busiest weekends of the year on the Jersey Shore and other parts of the Mid-Atlantic coastline. That puts a lot more people in harm’s way, including people who might be used to living on the coast and the hazards it poses.
“The greatest concern is that Hermine is likely to hover off the coast for several days, which means there will be multiple high tides coinciding with any potential surge,” Steve Bowen, a meteorologist with re-insurer Aon Benfield, said. “This will bring a very real risk of coastal inundation that could leave exposed properties facing damage. When you include the additional likelihood of periods of heavy rain and gusty winds, it all adds up to a big mess.”
The Mid-Atlantic could be in for historic flooding
It cannot be underscored enough that Hermine could be a sneaky strong storm that brings heavy surf and flooding to parts of the Mid-Atlantic. It may “only” be a tropical storm, but flooding forecasts on Sunday evening are in record territory. That’s why there’s a storm surge watch for the entire region.
Strong winds out of the east will add up to 5 feet of storm surge on top of high tide for much of the Jersey Shore. Water levels could reach up to 9 feet in Cape May, N.J., Atlantic City, and Lewes, Del.
— John Homenuk (@jhomenuk) September 2, 2016
This would mark the second time in a year some of those areas have dealt with major coastal flooding. A January Nor’easter steered icy waters ashore, inundating a number of areas.
— Ryan Maue (@RyanMaue) September 2, 2016
Though slightly less severe, parts of Long Island and Connecticut could see up to 4 feet of storm surge. And New York Harbor is forecast to receive about 3 feet of storm surge, which could have impacts on Zone A, the lowest lying areas on the city’s flood map. The National Hurricane Center has started issuing storm surge potential flood maps ahead of the storm (you can check the most recent one here).
Tropical storm-force winds could touch every state on the East Coast
Though the strongest winds will likely stay out to sea, every state on the Eastern Seaboard has a chance to feel Hermine’s sting.
On Friday morning, the National Hurricane Center forecast indicated 50 percent or greater odds for tropical storm-force winds — surface winds greater than 39 mph — from Georgia to the eastern edge of Long Island. Though unlikely, the risk of tropical storm winds over the next 5 days extends all the way to Maine. That’s why a tropical storm warning extends to Delaware and a tropical storm watch is in place from New Jersey to Connecticut.
Hermine will be sticking around for awhile thanks to a block
A few hours of rain, wind and high surf is bad enough, but a blocking pattern in the atmosphere means Hermine could make life miserable for days on end.
One heck of a Rex block pattern will keep Hermine locked in place off the Mid-Atlantic/NE Coast for 4-5 days. pic.twitter.com/0VHnpZS8Nm
— Anthony Sagliani (@anthonywx) September 2, 2016
Specifically, a Rex block pattern will set up, with a high pressure system over New England and Canada conspiring to keep Hermine trapped off the Mid-Atlantic for up to a week. While the worst impacts are expected on Sunday, the shore could continue to take a beating long afterward as waves eat away at beaches across the region.
Warm waters will also provide continued fuel for the storm
The same bathtub-warm water that’s been drawing people to the Jersey Shore this summer could also give Hermine a temporary boost in power.
Waters off the coast of New Jersey and Delaware are up to 9°F (5°C) above normal for this time of year. That’s in part why Hermine could strengthen back into a hurricane for a bit on late Sunday or early Monday.
The boost will be short-lived, though, as the storm’s newly strengthened winds will stir up the ocean and bring cooler deep waters up to the surface. That will eventually bring Hermine back down to a tropical storm.
This is not Sandy 2.0, but that doesn’t mean you shouldn’t take it seriously
Hermine is not as big or as strong as Sandy, nor is the blocking pattern that will likely lock its track in place. New York will also be unlikely to experience anywhere close to as severe a surge as it did during Sandy.
That’s the good news. The bad news is this is still a serious storm. Even if the flooding impacts aren’t as severe as forecast in the Mid-Atlantic, dangerous rip currents will make playing in the ocean a dangerous proposition. If you’re living in or planning to visit the Mid-Atlantic this weekend, think about that before setting foot in the water.
Climate change has a role to play in terms of sea level rise and ocean temperatures
Writing about the January flooding, storm surge scientist Hal Needham said at the time:
Sea level rise is an important component of these floods, and that is a clear signature of climate change. For most of the U.S. coastline, sea-level rise is a persistent, long-term threat, with surprisingly pernicious impacts. In coastal New Jersey the rate of relative sea level rise is around 1.0 -1.5 feet per century.
Even a few inches of sea level rise can lead to increased beach erosion, additional stress on seawalls and coastal flood defenses, and exacerbate flooding when accompanied by heavy rain. Rainfall runoff in most places is gravity-fed, requiring a slope to drain. Increased sea levels decrease this slope, slow the drainage, and exacerbate flooding, slightly inland and right at the coast.
In addition, warmer oceans are also one of the hallmarks of climate change. So while there’s no specific attribution work being done on this storm, there are some notable climate ties.