It became a tropical storm the next day in water cooler than 24 Â C ( 75 Â F ) , colder than the 26.5 Â C ( 80 Â F ) usually needed for tropical storms . Its transformation to a tropical system occurred over water cooler than 24 Â C ( 75 Â F ) , much colder than the 26.5 Â C ( 80 Â F ) usually required for tropical development .