(CNN) -- The National Hurricane Center increased Tropical Storm Colin's top sustained winds to 60 mph Thursday night after a hurricane hunter aircraft took fresh readings from 600 feet above the storm.
Colin's current northwest trajectory -- on a speedy 20 mph clip -- would bring the storm near Bermuda Saturday after a slow increase in intensity Friday night.
A tropical storm warning was in effect for the British island territory 470 miles to the north, meaning tropical storm force winds are expected in the next 36 hours.
The storm is not forecast to make landfall in the United States.
CNN's Sean C. Morris contributed to this report.