Tropical Storm Humberto formed near the Cape Verde Islands on Monday and was expected to strengthen into the first hurricane of the Atlantic storm season, forecasters at the U.S. National Hurricane Center in Miami said.
Rainbands and gusty winds from the storm were lashing southern Cape Verde, a nation of small rocky isles off the north African Coast with a population of about 531,000. It won independence from Portugal in 1975.
The storm had top sustained winds of 40 miles per hour (65 kph) and was centered about 105 miles (170 km) south of the island of Praia in Cape Verde.
Tropical Storm Humberto - approximate path as of Sept. 9, 2013
Humberto was moving west and was expected to swing to the north over open waters, strengthening into a hurricane with sustained winds of at least 74 mph (119 kph) early on Wednesday.
It was not expected to threaten the United States or any energy interests in the Gulf of Mexico.
Humberto was the eighth tropical storm of the Atlantic-Caribbean hurricane season, which runs from June 1 to November 30.
The season was on track to be above average for tropical storm formation. But so far this year, shearing winds and patches of dry, dusty air have prevented any Atlantic storms from strengthening into hurricanes.
The first hurricane of the season usually forms by August 10.
Since the dawn of the satellite era in the mid-1960s, the latest date for the first hurricane to arrive was set when Hurricane Gustav made its debut on September 11, 2002.
If Humberto achieves hurricane status any time after 8:00 a.m. EDT (1200 GMT) on Wednesday, it would replace Gustav as the modern-day record holder, the forecasters in Miami said.