The Hong Kong Observatory will enhance its provision of rain information on the Internet by releasing three-dimensional radar images on the Observatory's website starting from today (May 23).
In a press briefing on the new service, Senior Scientific Officer of the Hong Kong Observatory, Dr Cheng Cho-ming, explained, "Members of the public have ready access to information on the movement and development of rain areas on the Observatory's website. This will enable them to take necessary precautions against heavy rain in advance."
"A weather radar works by giving out radio waves and receiving echoes from rain drops in the air. The echoes enable the whereabouts of rain areas, as well as their movement, to be determined."
Members of the public will be able to view on the Observatory's website an animation sequence of three-dimensional radar images, for the past three hours and out to tens of kilometres away.
The three-dimensional radar images show the distribution and depth of rain areas. In general, rain areas of greater depth produce heavier rain, while shallower rain areas produce lighter rain.
Photos below show the radar image of extensive rain and thunderstorms affecting most of the New Territories and Lantau Island at 3 pm on May 9, 2001. The Observatory issued an Amber Rainstorm Warning for the occasion. Some places in Hong Kong received over 40 mm of rain that afternoon.
Photo A is the radar image at 3 pm on May 9,2001.
Rain areas are shown in greyish white colour.
Photo B shows the base map of the radar image
indicating the location of various places in Hong Kong.
Furthermore, photos below show the radar images of rain areas affecting Hong Kong in the night of May 8, 2001.
Photo C is the radar image at 9:30 pm on May 8, 2001
Photo D is the radar image at 10 pm on May 8, 2001.
Photo E is the radar image at 10:30 pm on May 8, 2001.
Members of the public are welcome to visit the web page on weather radar information at