Rare blue supermoon could make Hurricane Idalia worse. Blame gravity

As Hurricane Idalia barrels towards Florida's west coast, a rare celestial event - a blue supermoon - threatens to exacerbate the storm's impact.

The moon will be at its closest point to Earth, known as perigee, on Wednesday, coinciding with Idalia's expected landfall.

This supermoon, while providing a stunning visual spectacle, also intensifies the gravitational pull on Earth, leading to higher tides.

"The timing is pretty bad for this one," warns Brian Haines, the meteorologist in charge at the National Weather Service office in Charleston, South Carolina.

The heightened tides are expected to worsen flooding not only in Florida but also in states like Georgia and South Carolina. Haines' office has been alerting residents that parts of Charleston could be submerged by Wednesday night.

During a full moon, the sun and the moon exert their gravitational forces in the same direction, causing tides to rise above normal ranges. This effect is amplified when the moon is closer to Earth, resulting in even higher tides.

The National Hurricane Center in the US has projected a storm surge of up to 15 feet along parts of Florida's west coast, with up to 7 feet expected in the Tampa Bay area.

"Storm surge that can be taller than a person is a concern with any major hurricane. The tides and the influence of a supermoon can increase that somewhat," explains Brian Tang, associate professor of atmospheric science at University at Albany in New York.

Northwest Florida, particularly the region known as Florida's Big Bend area, is especially vulnerable to storm surge due to its geographical features. The continental shelf extends far out from the coast with a gradual slope, allowing the ocean to rise higher as hurricane winds drive the water onto land.

The inward curve of the coast can also concentrate the storm surge, making it even more dangerous.

In South Carolina, there are concerns that Idalia's path will take it near the historic city of Charleston and the surrounding Low Country, adding water to the already high tide forecasted.

"Wednesday evening looks really nasty for coastal flooding here," Haines warns, forecasting an 8.2-foot tide in Charleston which could result in widespread flooding in downtown Charleston.

Even with a 7.5 foot tide, some roads in the city could become impassable. As the supermoon rises and Hurricane Idalia approaches, residents are urged to heed warnings and prepare for potential flooding.