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Tuesday, 22nd September 2009

Acts of courage

Despite the havoc wrecked by Typhoon Koppu, Hong Kong quickly returned to normal. While the media reported some 50 casualties mostly incurred at the height of the storm, there was none in the general rush back to work the next morning (15 September). Hong Kong people can take pride in the civil and orderly society they are in. The transport operators should be congratulated for their immaculate planning and advance notice to members of the public.

Talking about advance notice, the Observatory started giving a specific timing for tropical cyclone signal changes this time, for instance by stating 4 hours ahead that the No. 8 signal would be replaced by No. 3 at about 10 a.m. The previous evening, SMS messages on the storm surge warning for low-lying areas were sent to relevant parties 10 hours ahead. These seemed to work well. However, such practice is not guaranteed, as it depends very much on the behaviour of the storm in respect of its movement and development. Each storm is different, and therefore needs to be handled differently.

What I really want to talk about is the difficulties the Observatory faced prior to the storm's approach. Thunderstorms in the previous evening (13 September) knocked out several weather stations, including the station at Cheung Chau which as an offshore island provides valuable wind information and is key to the operation of the Tropical Cyclone Warnings. Although the station has two wind sensors, one of which serves as a standby, both went out of action because of the thunderstorms' severity (6000 lightning strokes detected in an hour).

Figure 1
Figure 1 - lightning map, evening of 13 September 2009

In view of the urgency, Observatory colleagues headed off to Cheung Chau first time the next morning (14 September). They knew that time was not on their side as Koppu was moving in. After some effort, the wind speed sensor at the station was restored to normal. However, repair of the wind direction sensor was not possible as it required rigger service, which was not immediately available. It was thus decided that our staff should return before the suspension of ferry service and onset of stormy weather.

Figure 2
Figure 2 - radar picture showing the eye of Koppu shortly before midnight, 14 September 2009

Despite restoration of wind speed information, the station would go without wind direction information, which was very important to the public when it came to seeking protection from the full force of the typhoon. It then came to our mind that the next logical step would be to let people have the wind information from the back-up station, established on Cheung Chau beach not long ago. This was achieved at an amazing speed, and in a matter of hours the information became available on the Internet:

For those familiar with electronics and IT, both tasks were no small feat. Nonetheless, they were accomplished in half a day. This ensured that disruption to the flow of wind information at Cheung Chau to the public was kept to a minimum. I salute these dedicated colleagues.

I should also mention the emergency service personnel who tirelessly saved people, manned public shelters, carried out evacuation, and cleared the roads and fallen trees in time for the next morning's traffic --- all these at the height of the storm when most of the population was safely at home. It is time that we express appreciation to these courageous people.

B.Y. Lee

Last revision date: <17 Jan 2013>