Tropical Storm Arthur is projected to weaken tonight, but it will likely regain strength after entering the Bay of Campeche on Sunday.The 2008 Atlantic  hurricane season got off to an early start today when a tropical storm formed off the coast of Belize, one day before the season officially begins. Tropical Storm Arthur formed Saturday afternoon and quickly made landfall at the Yucatan Peninsula, near the border between Belize and Mexico. Both  countries issued a tropical storm warning for the peninsula's eastern coastline. In the Mexican state of Quintana Roo, ports were closed to small boats,  water sports were banned, and those living in coastal areas were encouraged to take precautions.