sentences:  Shortly after peaking, the hurricane turned to the north and gradually weakened as wind shear from an upper-level trough to its northwest increased.By early on November 17, the low-cloud circulation became partially exposed on the west side of the deep convection, and it is estimated that Sergio weakened to a tropical storm later that day.A ridge to its north and northeast turned the storm to the northwest and later to the west as Sergio gradually weakened.