(CNN) -- Tropical Storm Katia gained in intensity and speed Tuesday evening and is expected to become a hurricane by late Wednesday or early Thursday, the National Hurricane Center said.
As of 8 p.m. ET, Katia was about 750 miles (1,210 kilometers) west-southwest of the southernmost of the Cape Verde Islands off the coast of West Africa, and carried maximum sustained winds of 60 miles per hour (95 kilometers per hour). Earlier Tuesday, the storm's maximum sustained winds were 45 mph (72 kph).
Moving over warm waters in "a low shear environment" in coming days, Katia is likely to gain strength steadily, the hurricane center said on its website.
The storm was moving at west-northwest at 20 mph (32 kph), and was expected to continue that motion for the next few days, the hurricane center said. Earlier Tuesday, its speed was slightly slower -- 18 mph (29 kph). It is still about 1,700 miles east of the Windward Islands of the Caribbean Sea.
Katia "continues to look more impressive on satellite images" in terms of becoming a more organized system, the hurricane center said. It said upper-level outflow from Katia "is becoming well established" to its north, south and west.
Katia is the storm name that replaced Katrina in the revolving list of names, according to the hurricane center. The list of Atlantic hurricane names is repeated every seven years and this year the list that was used in 2005 is being reused.
A storm name is retired if it is used for a hurricane that caused major damage, as Katrina did to the U.S. Gulf Coast in 2005.
"The only time that there is a change is if a storm is so deadly or costly that the future use of its name on a different storm would be inappropriate for obvious reasons of sensitivity," the hurricane center said.