This is a good example of a satellite photo that clearly shows a trough out in the Atlantic Ocean. The wind flow in a trough is such that it can steer a hurricane away from the U.S. coast. When a hurricane (or tropical storm) approaches a trough, often times the wind flow of the trough acts to shear or rip off the delicate thunderstorm tops of the cyclone. The only catch about troughs is that they can be your best friend or worst enemy. Imagine poweful Hurricane Hugo approaching the Southeast Coast, had a strong trough been advancing towards the East Coast, then Hugo would have likely been turned out to sea- much like Edouard in 1996. However, if the trough enters the scene too late, like in the case with Floyd in 1999, then the turning effects of the trough only steer the hurricane right up the East Coast.