A rare occurrence of a blue supermoon might lead to higher-than-normal tides. This situation coincides with Hurricane Idalia hitting Florida’s western coastline, compounding the flooding issue from the storm.
On Wednesday, the moon was at its closest point to Earth, the same day when Hurricane Idalia struck with significant force as a Category 3 hurricane near Keaton Beach in the less populated Big Bend region of Florida. The hurricane brought sustained winds of around 125 mph (200 kph).
While a supermoon is often a captivating sight in photos of global landmarks, its stronger gravitational pull influences higher tides.
Brian Haines, the leading meteorologist at the National Weather Service office in Charleston, South Carolina, commented, “The timing for this combination is rather unfortunate.”
This phenomenon is expected to worsen tidal flooding not only in Florida but also in states like Georgia and South Carolina. Residents have been cautioned that parts of Charleston might be inundated by water come Wednesday night.
During a full moon, the sun and the moon’s gravitational forces align, causing tides to exceed normal levels. Kerry Emanuel, an esteemed atmospheric science professor at the Massachusetts Institute of Technology, explained that the moon’s pull is even more pronounced when it’s closer to Earth, resulting in higher tides.
In hurricanes, storm surges are often the most devastating aspect. The National Hurricane Center’s recent briefings projected potential ocean water surges of up to 15 feet (4.6 meters) along Florida’s western coast, while the Tampa Bay area might experience surges of up to 7 feet (2.1 meters).
The presence of a supermoon can exacerbate storm surges, which can already be life-threatening during major hurricanes. Brian Tang, an associate professor of atmospheric science at the University at Albany in New York, advised, “There’s a saying that you hide from the wind and run from the water, and hopefully people are heeding that advice.”
The region in northwest Florida where Hurricane Idalia made landfall is particularly susceptible to storm surges due to its geography. The continental shelf extending far from the coast, coupled with a gradual slope, allows hurricane winds to push seawater inland. The curved shape of the coast in that area, known as Florida’s Big Bend region, concentrates the storm surge, intensifying its impact.
In South Carolina, concerns are rising about Idalia’s trajectory potentially affecting the historic city of Charleston and the surrounding Low Country area. This would exacerbate the forecasted high tide. Haines stated, “Wednesday evening appears to be challenging due to coastal flooding.”
The weather service predicts an 8.2-foot (2.5 meter) tide in Charleston on Wednesday evening, likely leading to extensive flooding in downtown Charleston. Even a 7.5-foot tide (2.3 meters) can render some roads impassable and flood city streets.