sentences:  Within a day of being classified, the system intensified into Tropical Storm Guillermo, the seventh named storm of the 1997 season.By the afternoon of August 1, a strong central dense overcast, an area of high, thick clouds, developed over the center of circulation, prompting the NHC to upgrade the system to a Category 1 hurricane on the Saffir–Simpson Hurricane Scale.Throughout the next day, the system gradually developed an eye within the central dense overcast, leading to further strengthening.