Predicting winds of change

PUBLISHED : Thursday, 23 February, 1995, 12:00am
UPDATED : Thursday, 23 February, 1995, 12:00am

MANY Hong Kong people would feel lost without their weather friend 'Freddie'.

Freddie, the cartoon figure that appears daily on television weather report, signals whether people should bring along an umbrella, a windbreaker or perhaps, a pair of sun-glasses the next day.

The real Fred, however, are 15 meteorologists who work around the clock on shifts at the Royal Observatory's Central Forecasting Office (CFO), producing the most updated weather bulletins for the press, radio and television.

'The five-minute forecast on TV or radio is actually a much simplified version of all the complicated data we deal with at our office,' said CFO senior scientific officer Poon Hoi-to.

'Information on the atmospheric conditions files in each day from every source, including ships, aircraft, land stations, weather buoys, numerical reports from overseas, weather satellites and radars,' he said.

But thanks to modern technology, almost all the weather input is now transmitted electronically to the century-old observatory, which has gone highly automated.

A network of about 20 weather stations in the territory, for instance, would automatically send readings of temperature (from thermometers), amount of rain (from rain gauges), wind speed and direction (from anemometers) and humidity (from the dry and wet bulbs) to the computers at the CFO.

'But we still rely on the eye to measure visibility,' said Mr Poon, who heads a forecaster and an experimental officer in one of the three daily shifts.

Mr Poon described an interesting procedure that takes place in King's Park each day: an officer would release a balloon bearing instruments that measure soundings of wind, temperature, pressure and humidity in the upper-air of up to 30 kilometres.

One of the observatory's important tasks is issuing warnings of tropical cyclones which knock off oil rigs, disrupt shipping and takes lives. The office is at its busiest during the typhoon season from June to October.

'We routinely produce a short-term forecast of the next three to six hours, and a longer one of up to six days ahead,' Mr Poon said.

For the latter, the CFO uses numerical weather prediction models produced by two meteorological centres operating in Europe and Britain.

But even though CFO officers work in a highly scientific environment, the numerical data and imageries from instruments and satellites could never produce a made-to-measure scientific formula for the outlook for the next day.

'Weather forecasting is not an exact science,' explained Mr Poon. 'There are weather stations separated by as wide as 100 kilometres. This does not provide us with sufficient information to formulate forecast.' After all the data collecting and plotting of weather charts, it still took a joint analysis from a group of experienced senior meteorologists in two daily conferences to come up with the nearest forecast, Mr Poon said.

The observatory, nevertheless, has received a rating of between 72 and 76 per cent in average forecast accuracy in public surveys over the last few years.

A DEGREE-holder in either physics, mathematics, meteorology, computer science or electronic engineering can enter as an experimental officer (assistant forecaster) at the Royal Observatory's Central Forecasting Office.

Upon training and passing of internal examinations, one may eventually become a senior forecaster (scientific officer) and chief scientific officer. Form Five science graduates may apply to be scientific assistants who collect and disseminate atmospheric data.