Tropical Storm Erin formed in the eastern Atlantic Ocean on Monday, forecasters said. The storm was expected to strengthen later in the week and could become the Atlantic's first hurricane of the season.

Gradual strengthening was forecast over the next several days and forecasters said Erin could reach hurricane intensity by the latter part of the week.

Erin could become a major hurricane, a designation that occurs when a storm's wind speeds reach 111 mph or higher, classified as a Category 3 hurricane. Should it strengthen as meteorologists expect, Erin could become not only the first hurricane of the season but also its first major hurricane.