THE huge balloon outside the Science and Technology pavilion is not an ''Eat at Joe's'', restaurant advertisement.
It is in fact a highly-sensitive weather gauging device which measures various atmospheric changes and is a key element in weather forecasting - that noble profession, which cynics believe still uses ouji boards and roulette wheels to tell us the next day's forecast.
The Royal Observatory's exhibits at the Expo are designed to make the public more aware of the huge advances that have been made by meteorologists over the past few years - and also silence a few critics.
Satellites, radar, automatic instruments and high-speed computers are used to help weathermen assess the present weather situation and calculate the evolution of approaching systems over the coming days with reasonable confidence.
As the technological aspects of computers, satellites and radar improve, forecasting should become even more accurate and longer in range. Perhaps you could even plan holidays around the weather: ''No rain in Bermuda from October 10-20, 1994, let's go there, George''.
On a more important note, while some weather systems bring mere discomfort, others usher in floods, typhoons and their associated deaths and damages.