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Monday, 23rd June 2008

Taking leave and black rainstorm

I have not written for a while because I took two weeks of leave and because much work awaited me on return.

Living in big cities dictates that our bodies have to work like a machine in high gear. It is easily worn out over time and efficiency comes down. The machine might even break down. So it has to be stopped from time to time for maintenance. Fortunately, we are living things and have the inherent capacity to repair ourselves during rest time. From this perspective, taking leave is part of work. Taking good rest during well-earned leaves is being responsible to the job itself.

The Observatory issued the Black Rainstorm Warning on 7 June while I was on leave at home. This was the first time in more than a decade for me to be a bystander in a rainstorm warning situation. Like fellow citizens, I relied on the radio and the internet to watch the evolution of the weather situation and to learn about the subsequent incidents.

The rain on 7 June was very characteristic of summer. It was very unevenly distributed and was particularly heavy in rather localized areas. The attached map fig. 1 shows the rain which fell in Hong Kong between 8 a.m. and 9 a.m. More than 100 millimetres were recorded in Kowloon, northern Hong Kong Island and northern Lantau. The south-eastern part of Hong Kong Island got less than 10 millimetres while the north-western New Territories got virtually nothing. We often say that Hong Kong is small. But due to the hilly terrain, rain could be highly variable within the territory itself.

At that time, like weather fans who discussed the subject on the internet, I was puzzled to see the radar scope showing rain areas which kept on converging on Hong Kong (see attached fig. 2). Even after I studied the weather charts later, it was still not easy to understand. In fact, modern meteorological observations still do not cover the 3-dimensional atmosphere fully. In the absence of a complete knowledge of "the present" in terms of the weather situation, it is inevitable that the weather in "the future" is not completely predictable.

Although modern technology is more advanced than before, we must remain humble in the face of the great complexity of nature. We have to respectfully recognize that the great natural forces do determine their own course.

C Y Lam

Rainfall distribution 8-9 a.m.
Figure 1: Rainfall distribution 8-9 a.m.

Radar picture 8:30 a.m.
Figure 2: Radar picture 8:30 a.m.

Last revision date: <17 Jan 2013>