The National Hurricane Center began issuing advisories on Potential Tropical Cyclone Eight on Sunday afternoon. The "potential tropical cyclone" terminology is used when a disturbance does not meet the criteria to be a tropical depression or storm, but could do so and affect land within 48 hours. This allows the National Hurricane Center to begin issuing alerts and forecasts for the system well in advance of landfall.

Tropical Storm Warnings have been issued from Edisto Beach, South Carolina to Ocracoke Inlet, North Carolina. Tropical storm-force winds now extend 175 miles from the center of circulation, mostly on the northern side. The storm is projected to make landfall in South Carolina with maximum sustained winds around 50 mph.

Lately, the area of low pressure in question has been located along a frontal system a few hundred miles off the southeast U.S. coast. If the associated front dissipates and thunderstorm activity can become sufficiently organized, a tropical or subtropical storm could form as the system moves northwestward over the warm waters of the Gulf Stream. Should that occur, the disturbance would take the name Helene.

To be a tropical storm, an area of low pressure must originate over tropical or subtropical waters, have a closed surface wind circulation, possess a well-defined center, maintain a base level of organization, and gain its energy primarily from warm ocean waters.

A subtropical storm is similar to a tropical storm in the sense that the storm originates over tropical or subtropical waters, and has a closed surface wind circulation and well-defined center. However, subtropical storms also gain energy from other sources in addition to warm ocean water, most commonly an upper-level trough or area of low pressure. It is possible that this system will be subtropical in nature.

Terminology aside, subtropical storms can still bring impacts similar to that of a tropical storm. And regardless of any tropical or subtropical development, gusty winds, heavy rain, flooding, storm surge, and tornadoes are likely across portions of the U.S. Southeast and Mid-Atlantic coast. Fortunately, this storm will not be an issue for Louisiana.