What is the main instrument for taking measurements of a tropical cyclone far out at sea?

Satellite imaging is the primary instrument used for tracking and measuring tropical cyclones in the deep ocean, according to the Weather Channel. Tropical storms tend to form far away from land, putting them out of range of radar, airplane and weather buoy measurement.

Satellite imaging can provide valuable information on a tropical cyclone's earliest days. Satellites can track cloud movement and density, giving information about a storm's path and areas that may be affected. Once the storm approaches land, it may come within range of airplane reconnaissance and Doppler radar, which can provide a more complete picture of the storm's makeup and allow for more comprehensive forecasting.