Tropical cyclones develop over the ocean and spend most of their lives over water.  As conventional observations over the ocean are sparse, satellite analysis is by far the most important method in locating the centres of tropical cyclones. 

The appearance of a well-formed eye is a definitive indicator of where the tropical cyclone is (Figure 1). If an eye is absent, it is still possible to obtain a reasonable estimate of the centre by tracing the spiral rain bands of the storm (Figure 2) or by studying the relative motion of cloud features near its centre (Figure 3). 

Satellite pictures are now received at half-hourly intervals by the Hong Kong Observatory and form a near real-time observational basis for tracking tropical cyclones.  Combining with other methods in locating the tropical cyclone, the centre of a tropical cyclone are plotted on weather map to show its movement (Figure 4).