Tropical Storm Fiona formed Wednesday afternoon in the middle of the tropical Atlantic Ocean, but forecasters said it poses no threat to coastal areas.

The season's sixth tropical storm is moving northwest at around 16 miles per hour (26 kilometers per hour) with maximum sustained winds of 40 miles per hour, the Miami-based National Hurricane Center (NHC) said.

Located some 920 miles west of Cape Verde, the storm represents no threat to land, the NHC added.

"There are no coastal watches or warnings in effect," the center said in a statement.

Fiona's strength is expected to build over the next two days but not to hurricane force.

Although the Atlantic hurricane season officially runs from June 1 to November 30, this year's first hurricane -- Alex -- formed in January during an unusual weather event.

The Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) initially estimated the Atlantic would see between 10 and 16 storms this year, but updated its prediction to 17 last week.

"The season is still expected to be the strongest since 2012," the NOAA said in a statement.

Tropical storms Bonnie and Colin formed between late May and early June, and Danielle appeared in late June. Earl became a hurricane earlier this month, leaving 45 dead in Mexico.

Last year's number of storms was below average, with 11 tropical storms in the Atlantic, six of which became hurricanes, including two major ones.