28 Jun 2021 | 05:41 PM UTC
US: Tropical Depression Four forms off coast of South Carolina; landfall likely as tropical storm late June 28
Tropical Depression Four forms off coast of South Carolina, US, June 28. Landfall likely as tropical storm the evening of June 28.
Event
Tropical Depression Four has formed in the Atlantic Ocean off the coast of South Carolina. As of 11:00 EDT June 28, the system's center of circulation was approximately 180 km (110 miles) east-southeast Charleston, South Carolina. Forecast models indicate the system will continue tracking west-northwest, strengthening into a tropical storm and making landfall near Kiawah Island, South Carolina, the evening of June 28. The system will subsequently weaken back into a tropical depression as it moves further inland across northern Georgia and into south-central Tennessee through late June 29 before it dissipates by early June 30.
Government Advisories
A tropical storm warning has been issued for the coastline between Edisto Beach and South Santee River, South Carolina. Authorities will likely issue new warnings or update existing advisories throughout the system's progression. Weather warnings could remain active even after the system's immediate threat has diminished, as some areas may still be highly susceptible to rain-induced hazards. The possibility of localized evacuations cannot be discounted if weather conditions prove particularly hazardous.
Hazardous Conditions
Forecast models indicate Tropical Depression Four will produce 2.5-7.6 cm (1-3 inches) of rainfall along the coasts of South Carolina and Georgia. Further inland, the system could produce 2.5-5 cm (1-2 inches) of rain across Upstate South Carolina, the Piedmont of Georgia, and northeastern Alabama. The system will likely also likely cause storm surge of 30-90 cm (1-3 feet) from Port Royal Sound to the South Santee River in South Carolina. Frequent lightning and strong winds are also possible over the coming days.
Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, and rivers, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall. Flooding could isolate some communities for several days. Prolonged sea swells and storm surge generated by the system will likely result in coastal flooding as the system approaches land. Persistent onshore flow could make it difficult for surge to recede and for water levels to decrease in coastal river catchments.
In addition to the heavy rain, flooding, and storm surge, the tropical depression could produce damaging wind gusts. Localized power outages due to uprooted trees and toppled utility lines are possible. Rain-induced landslides are also possible in hilly areas where the ground is loose and unstable.
Transport
Tropical Depression Four will likely cause some transport disruptions across portions of South Carolina and northern Georgia. Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Areal flooding in urban locations could also result in severe traffic congestion, while strong winds will pose a hazard to high-profile vehicles. Heavy rain and low visibility may trigger flight disruptions at regional airports. Rough seas could also complicate maritime vessel movements along the South Carolina coastline.
Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after conditions have improved. If there is severe damage to infrastructure, repair or reconstruction efforts may exacerbate residual disruptions.
Advice
Activate contingency plans in areas where officials forecast tropical storm conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the high potential for severe flooding and storm surge. Stockpile water, batteries, and other essentials in advance. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents in waterproof containers. Observe strict food and water precautions, as municipalities could issue boil-water advisories following flooding events. Take precautions against insect- and waterborne diseases in the coming weeks. Keep any necessary medications in a waterproof container.
Plan accordingly for protracted commercial, transport, and logistics disruptions in areas in the path of the storm, especially if vital infrastructure is damaged. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred. Confirm flights before checking out of hotels or driving to the airport; clearing passenger backlogs may take several days in some locations.
