Guessing to go from forecasts

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.

Accurate forecasts of impending storms and the like are useless if the information does not reach the public.

Fortunately, the Royal Observatory possesses an advanced telecommunications system for the rapid-fire sending of weather information to the Hong Kong media.

The next step, of course, is to link up with weather services throughout the world. The Royal Observatory predicts by the year 2001 anyone with hand-held computing and telecommunication devices will be able to access long-range forecasts issued anywhere in the world.

So, theoretically, you could call the Cannes weather bureau in France to see if it's worth sailing there or to Tenerife.

The observatory's display takes the viewer through animated time elapse sequences from radars and satellites and also computer-generated three-dimensional graphics.

Just one question remains. Will life be boring when we know exactly what the weather is going to be like day after day? Maybe, but think of the money you will save on lost umbrellas.