First 2016 U.S. tropical storm warning issued for South Carolina

The bulletin, posted by the National Hurricane Center in Miami, warned of tropical storm conditions reaching South Carolina's coastline within 36 hours - in the midst of the Memorial Day holiday weekend - from the Savannah River north to the Little River Inlet.

Tropical storms are defined as a cyclonic weather systems packing winds with sustained surface speeds ranging from 39 to 73 miles per hour (63 to 119 kilometers per hour).

The current threat to South Carolina was posed by the formation of a tropical depression off the southeastern United States, marking the second such weather system of 2016, following one that grew into Hurricane Alex in the far eastern Atlantic in January, according to the Hurricane Center.

Alex, a rare wintertime storm that threatened the Azores island group far off the coast of Portugal, never came near the United States.

The latest weather system, now designated Tropical Depression Two with maximum sustained winds of 35 mph (55 kph), was expected to strengthen into a tropical storm later on Friday night or on Saturday, the Hurricane Center said.

At that point, it would be named Bonnie, and by next Wednesday would rank as the first of the 2016 Atlantic hurricane season, which officially runs from June 1 to through Nov. 30.

Tropical storm conditions were expected to reach coastal South Carolina by Saturday night, according to forecasters.

The depression's center on Friday evening was located near latitude 28.5 North, longitude 74.7 West, the Hurricane Center said. The weather system was expected to produce 2 to 4 inches (5 to 10 cm) of rainfall from the upper coast of Georgia through eastern South Carolina and into southeastern North Carolina.

Tidal storm surge flooding of 1 to 2 feet (30 to 60 cm) above ground level also was expected in the storm warning area, the Hurricane Center said.

U.S. meteorologists have predicted an increase in the number of named storms this hurricane season compared with below-average numbers during the past three years.

The National Oceanic and Atmospheric Administration forecast a 70 percent likelihood of 10 to 16 named storms in the upcoming hurricane season. By comparison, 2015 saw 11 named storms, including four hurricanes, of which two were major, according to federal data.