Debby to impact Georgia, Carolinas with life-threatening flooding and storm surge this week
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.
With potential feet of rain in the forecast from Debby, the city of Charleston is taking action to help keep people safe through extreme overnight rainfall.
Now with Debby well inland over the southeastern United States, AccuWeather meteorologists continue to raise concerns of the tropical storm's slow forward speed that will lead to excessive rainfall from southeastern Georgia to coastal areas of the Carolinas. So much rain may fall to lead to life-threatening conditions.
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.
The center of Debby was drifting into southern Georgia on Monday afternoon, but the shield of rain and gusty winds extended to the north and east by a couple hundred miles.
Even though Debby may officially be only a tropical storm 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.
Life-threatening rainfall possible for Georgia, Carolinas
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.
Families and businesses in the South Carolina Lowcountry are being warned to prepare for widespread and dangerous flooding impacts from Debby.
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 will likely surpass those historic 100-year values. 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.
Enough rain will fall over central portions of the Carolinas to lead to incidents of urban flooding as well as rises on small streams and some rivers. Downpours may also extend as far to the west as the southern Appalachians.
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 southward can result in elevated storm surge values between 6-10 feet.
"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.
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.
Precursor of Southeast U.S. drought to be a factor
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.
AccuWeather Lead Hurricane Expert Alex DaSilva explains the long-term impacts of Hurricane Debby as it slowly tracks north across the Southeast U.S. after making landfall in Florida on Aug. 5.
Implications as Debby travels along the coast
If Debby maintains strength as a tropical storm as it tracks northward along the mid-Atlantic coast and eventually the Northeast, impacts ranging from heavy and perhaps flooding rainfall, as well as 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.
Elsewhere in the tropical Atlantic, AccuWeather meteorologists are tracking another feature across the Caribbean that may evolve into a tropical depression or storm late this week and this weekend in the Gulf of Mexico.
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