Making sense of typhoons by flying into the eye of the storm

Late in the afternoon of August 13, while the No 3 signal was issued in Hong Kong, the Observatory meteorologist Wong Wai-kin was in a small plane over the South China Sea, flying at 2,400 metres, just above the main clouds swirling around Severe Typhoon Utor.

The centre of the storm was nearby, and the plane began descending through dense clouds. Rain pummelled the windows. Visibility came down to almost zero, as if in thick fog. In the violently swirling air, the plane was tossed about like a sampan on two-metre waves.

After about 15 minutes, the plane emerged from the cloud, entering clear air, with a calm sea below and blue sky above: it was in the eye of Utor. For Wong, it was a precious moment: he was now the first of the Observatory staff to fly into the eye of a severe typhoon. It was also a significant milestone in research on typhoons, the west Pacific's mighty, sometimes devastating, storms.

Observatory director Shun Chi-ming cites three of the most lethal: "More than 10,000 people died during storms in 1906 and 1937, and in 1874, more than 2,000 died."

In 1874, some weather-wise locals had an inkling that a typhoon was approaching, but there was no official warning as it was still nine years before the Observatory would be established. In 1906, a warning was issued just 20 minutes before gales began blowing. By 1937, forecasts had improved, yet although more than a day's notice was given about an approaching typhoon, it arrived overnight and the onslaught took many by surprise.

From 1966, the Observatory began using satellite images to help with routine forecasts. Satellite data is now pivotal to analysing tropical cyclones like typhoons. Besides light in the visible spectrum - useful only in the day - it uses microwaves and infrared radiation to obtain estimates of upper-air cloud movements and temperatures, as well as wind speed and direction near the surface of the sea based on signals scattered by waves.