NEW YORK (REUTERS) - Bertha, the second named storm this Atlantic hurricane season, has weakened to a tropical depression but was still expected to bring heavy rain and possibly life-threatening flash floods to parts of the Carolinas and Virginia, the US National Hurricane Centre (NHC) said on Wednesday (May 27).

The tropical depression, which now packed maximum sustained winds of 55kmh, is located about 105km north-northwest of Charleston, South Carolina, the Miami-based forecaster said.

Earlier in the day, the storm made landfall along the South Carolina coast east of Charleston.

The weather system was expected to keep weakening throughout the course of the day, experts said, and no coastal watches or warnings were currently in place.

Bertha could dump between two and four inches of rain on the affected areas, and the NHC warned that due to previous inclement weather conditions the additional rainfall could produce life-threatening floods.

Experts had been tracking the system for a couple of days, NHC meteorologist Dennis Feltgen told Reuters, adding that it is not uncommon for storms to form close to the coastline and develop quickly, as Bertha did.

US forecasters expect an above-normal 13 to 19 named storms during the 2020 Atlantic hurricane season, the National Oceanic and Atmospheric Administration's (NOAA's) Climate Prediction Centre said earlier this month.

NOAA forecasters estimate three to six major hurricanes packing winds of at least 178kmh may form.

The last two years have seen an above-average number of named storms, with 18 last year and 15 in 2018.