Forecasters (above) plot the
most probable future track of a storm on a surface chart. The course of the storm will also be followed on the upper-air charts at rear. Weather reports are received from the masters of 60 ships. Sensitive instru- ments (right) make record- ings of rainfall, pressure, temperature and wind.
Information on approaching storms is given over the radio at frequent intervals, but visual signals still play an important part in the warning system. The No 1 signal (below) means that a tropical cyclone is centred within 400 nautical miles of Hong Kong. Other signals indicate winds up to 64 knots or more.