When tropical systems are boiling up, meteorologists rely on remote sensors such as satellites to observe the cloud structure and track the movement of hurricanes and tropical storms.

Although it's possible to derive wind speeds from satellite data, having surface sensors is a real help.

In the oceans and Gulf of Mexico, that surface data comes from buoys.

The National Data Buoy Center designs, operates and maintains a network of buoys and coastal stations to collect weather information. The center is part of the National Oceanic and Atmospheric Administration.

The U.S. network uses about 90 buoys and 60 coastal-marine automated network stations. Most of the yellow buoys are near the coastline, with the few that are farther offshore providing data that helps forecasters decide the direction of tropical systems. The coastal stations, also known as C-MAN stations, are located on piers or outcroppings.

The buoys and C-MAN stations use solar energy to power their batteries. They measure water and air temperature, wind speed and direction, and barometric pressure. The buoys also can measure wave height.

The data is transmitted via satellite to a central collection site in Virginia.

The buoys can face rough weather and are moored or anchored using anything from chain in shallower waters to polypropylene rope in deeper waters.

The buoys are serviced every two years to combat erosion. Most of the work is done by the national center, although some of the remote buoys are repaired by the U.S. Coast Guard.