Hurricane season technically ends on November 30.But Tropical Storm Sebastien, at present 660 miles from Bermuda and drifting north-northeast into the Atlantic, could attain hurricane strength later this week.At 11am, Sebastien was moving at 8mph with winds of about 60mph, with potential to grow into a short-lived Category 1 hurricane tomorrow, according to the Bermuda Weather Service.Its expected trajectory will keep it well away from Bermuda, and a cold front is predicted to hit the storm by this weekend.Sebastian marks the eighteenth named storm of the season.