If Debby stalls along the Southeast coast this week, there could be dire implications for locations in Georgia and the Carolinas in term of flooding and storm surge.
Homes and businesses were boarded up in Florida Keys are, as well as sandbags being filled, in preparation for tropical storm Debby. Heavy rain and flash flooding are in the forecast.
As Hurricane Debby advances across the far eastern Gulf of Mexico and the Florida landfall threat looms, AccuWeather hurricane experts continue to look ahead at what impacts Debby may bring in the coming days.
Over the next several days, Debby is projected to linger along the Southeast U.S. coast to produce significant flash flooding, gusty winds and prolonged coastal inundation. AccuWeather expert meteorologists say that there is a growing threat of relentless rainfall and flooding impacts as the storm slowly tracks from northern Florida to parallel with the Georgia and Carolina coast.
From late Monday evening to late Tuesday, the center of Debby will progress northeastward into southeast Georgia. While residents across the Carolinas observed intermittent showers and thunderstorms around through the end of the weekend, the initial push of heavy rain and gusty winds will continue to spread across Georgia and portions of South Carolina into Monday morning.
Even though Debby may officially be only a tropical storm or Category 1 hurricane along the Georgia and Carolina coasts, its impacts from life-threatening storm surge and flooding rain, as well as the effects of strong winds on property and utilities, will result in Debby being a 3 on the AccuWeather RealImpact™ Scale for Hurricanes in the United States.
The track, intensity and forward speed of Debby along the Southeast coast will determine how severe and long-lasting that the impacts will be, and forecasters say that the upper-level pattern in the atmosphere will govern the storm’s movement.
“Debby is projected to slow down along the Southeast coast early this week. Upper-level winds, which typically steer tropical storms and hurricanes, will be very light within this zone, which can cause the storm to nearly stall out for a time,” explained AccuWeather Meteorologist Brandon Buckingham.
Buckingham added that depending on the exact location of the storm in proximity to the Southeast coast, a prolonged, potentially multi-day period of heavy rain, strong wind gusts and persistent onshore flow are all possible from coastal Georgia through the coastal Carolinas.
For locations like Savannah, Georgia, three-day rainfall totals ranging between 10.3 to 16.0 inches occur roughly every 100 years, and the range for Charleston, South Carolina, is similar at 10.9 to 13.1 inches.
The heaviest swath of rainfall totals of 18-24 inches is expected to occur across far southeast Georgia and southern South Carolina, including around the cities of Savannah and Charleston. Rainfall across this zone may contend with or surpass those historic, 100-year values if even around a foot of rain falls within 72 hours.
The AccuWeather Local StormMax™ for rainfall in the Southeast U.S. is 32 inches.
Rainfall totals such as these represent enough rain to trigger significant urban and river flooding, especially in coastal cities prone to flooding. Once river flooding begins, it may take a few weeks for waters to recede in the lowlands of Georgia and the Carolinas.
However, if the storm slows down and lingers over one spot longer than anticipated, the combination of storm surge and torrential rainfall can result in widespread major flooding that can become life-threatening. Impacts can range from impassable roadways and long-lived transportation delays to structural damage.
“If there is heavy rain inland across the Carolinas, that water will eventually enter rivers and other waterways that flow toward the coast. Water flowing toward the coast, coupled with the persistent onshore flow, can back up the rivers because they won’t be able to drain, further amplifying what can already be major flooding concerns along and near the coastal areas,” explained AccuWeather Chief Meteorologist Jon Porter.
Storm surge can rise to 3-6 feet from the Georgia coast through North Carolina, but forecasters warn that the persistent onshore flow and the orientation of the coast in South Carolina from Charleston on southward can result in elevated storm surge values between 6-10 feet.
Tropical storm and storm surge watches were in effect Sunday morning along south and eastern Georgia and South Carolina.
“Impacts [from Debby] could be greatly amplified and would occur over a long period of time [along the Southeast coast]- including large waves, significant beach erosion and major coastal flooding, which can be at a level that may permanently alter beaches and other coastal areas,” stated Porter.
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Coastal inundation is known to be worse during times of high tide when water levels peak throughout the day. Due to the long duration of the onshore flow expected across Georgia and the Carolinas, numerous rounds of tidal rises will overlap with Debby’s stay along the Southeast coast and elevate the impacts from storm surge.
Soaking and prolonged rainfall across drought-stricken areas will help to quench the dry soils and recharge groundwater reserves this week; however, the onset of intense rainfall over parched surfaces can more easily result in rapid runoff and flash flooding.
A large zone across South Carolina is currently experiencing moderate to severe drought conditions, with a sector in northeast South Carolina even facing extreme drought levels, according to the U.S. Drought Monitor.
Debby is projected to remain at tropical storm strength as it advances along the Southeast and mid-Atlantic coast. As wind bands wrap around the center of the storm, gusts of 40-60 mph can expand inland from northern Florida through eastern Virginia, portions of Maryland, Delaware and southern New Jersey.
Gusts can even exceed 60 mph from southeast Georgia into South Carolina as the storm advances northward early this week.
If Debby maintains strength as a tropical storm as it tracks northward along the mid-Atlantic coast and eventually the Northeast, impacts ranging from persistent rain and locally gusty winds to travel delays can spread across the region.
“After the rounds of rain [across the Northeast] over the last week, the ground will likely be saturated in some areas. There is the potential at least for urban flooding and travel delays, and perhaps more serious widespread flooding as Debby shifts up the coast,” noted AccuWeather Senior Meteorologist Alex Sosnowski.
AccuWeather forecasters urge residents from the Southeast to the Northeast to closely monitor the track of Debby and the impacts expected for their area.
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