https://phys.org/news/2018-10-nasa-weakening-tropical-storm-nadine.html

In general, wind shear is a measure of how the speed and direction of winds change with altitude. In order to understand how it affects a tropical cyclone or hurricane, think of a tropical cyclone as a vertical rotating cylinder. The different levels of rotating winds in the center of Tropical cyclones need to be stacked on top each other for the storm to strengthen. If there are outside winds pushing against the cylinder near the top, it affects the balance of the entire cylinder and that's what happens when vertical wind shear pushes against a storm. It pushes the center and weakens (or wobbles) the rotation of the entire cylinder (storm).

At 11 a.m. EDT (1500 UTC) on Oct. 11, the National Hurricane Center reported the center of Tropical Storm Nadine was located near latitude 14.1 degrees north and longitude 34.0 degrees west. That's about 645 miles (1,035 km) west of the southernmost Cabo Verde Islands. Nadine is moving toward the northwest near 8 mph (13 kph). A turn toward the west-northwest with a similar forward speed is expected later today, followed by a turn toward the west by the weekend. Maximum sustained winds are near 60 mph (95 kph) with higher gusts. Some weakening is forecast during the next 48 hours. Gradual weakening is expected during the next couple of days, and Nadine is forecast to degenerate into a trough of low pressure over the weekend.