The flooding will be exacerbated by a destructive combination of already higher than normal tides and a developing storm system, sending tide levels above 8 feet for Charleston and over 10.5 feet near Savannah, signaling a major flood stage along the coast.
“It looks like an almost perfect combination of astronomical influences and meteorological conditions,” said Blair Holloway, a meteorologist from the National Weather Service in Charleston.
Based on the shape and orientation of the Carolina and Georgia coast, these northeasterly winds tend to push water toward coastal communities, bringing the most significant concerns for coastal flooding in addition to those caused by tropical systems.
“Now you look at a foot to maybe more than a foot and a half of extra water, almost like a splash, which is the extra water due to the wind, accumulated on the usually already high astronomical tides,” Ron Morales, a meteorologist at the National Weather Service in Charleston, told CNN Weather.
The effects of the floods and the development system will send water levels above 8 feet on Friday and Saturday morning, peaking at 8.6 feet on Saturday morning. This is expected to be the highest level seen since Hurricane Irma (9.9 feet) in September 2017 and nearly the highest level for a non-tropical event (8.8 feet) on January 1, 1987.
“Roads, even areas you haven’t seen flooded in long enough, could see flooding. Even some structures could be flooded by these water levels and some roads could be cut off,” Morales said.
Farther from the coast, at Fort Pulaski, Georgia, a few miles from the historic city of Savannah, waters are also expected to reach over a major flood stage, forecast to peak at 10.6 feet on Saturday morning.
Since 1936, a peak tide of 10 feet or higher has been observed only 18 times.
“If we reach or exceed 10.5 feet, it will rank as at least the fourth highest tide recorded and would be the highest nontropical recorded. We have never seen the tide exceed 10.43 feet unless it relates to a tropical. System, this would be extremely rare if not unprecedented, ”said Blair Holloway, a meteorologist at the NWS in Charleston.
“We are particularly concerned about the only road in and out – which goes from Savannah to Tybee Island – the road was raised a few years ago, but at 10.5 feet we expect problems there,” Morales told CNN Weather. .
Floods of this magnitude have historically been reserved for the massive increase that comes with tropical systems, but in a warming world with rising seas, the tides are turning, both metaphorically and literally.
“Long-term sea level rise due to rising global and ocean temperatures resulting from climate change is making coastal flooding events like this occur more frequently, with worsening effects of higher flooding,” said Brandon Miller, CNN meteorologist and leader of climate crisis. “Sea levels have risen nearly a foot since the early 1900s, raising the baseline from which these floods occur – pushing troublesome flooding storms into record territories that previously came only in the strongest storms like hurricanes. “
“We have a lot more coastal flooding now than a decade or two ago,” Morales said. “We’ve certainly seen an increase over the last five to 10 years from the number of times we’ve reached that minimum threshold of 7 feet, which is what we call coastal flood advice.”
In Charleston, an 8-foot water level has been reached 36 times in the last 100 years, but 22 of those times have been since 2015. Similarly, at Fort Pulaski, near Savannah, a peak tide of 10 feet or higher has only been observed 18 times since 1936 , but 11 of those 18 occasions have occurred since 2015.