The Observatory launches a new lightning location information service

The Hong Kong Observatory announced today (21 June 2005) the launch of a new lightning location information service. Members of the public can make use of the lightning location information to identify areas affected by thunderstorms.

The locations of lightning strikes will be displayed in graphical form on the Observatory's Website (http://www.weather.gov.hk/wxinfo/llis/index.htm) (Figure 1) and Personal Digital Assistant (PDA) Website (http://pda.hko.gov.hk/llise.htm). The webpage will be updated once every 5 minutes enabling visualization of the movement of thunderstorms through animation of these lightning location maps.

For easy reference of the lightning locations, Hong Kong is divided into four regions, namely New Territories West, New Territories East, Lantau, Hong Kong Island and Kowloon (Figure 2). To raise the awareness of users, an alert function will be provided on the lightning webpage. An alert will be displayed on the webpage when the network has detected lightning in one of regions as selected by the user (Figure 3).

In addition to the graphical display, a condensed version of the lightning location information will be available in the hourly weather bulletin for radio and television broadcast. The information will also be accessible from the Dial-a-Weather system (1878 200) which will be updated once every 15 minutes.

When utilizing the lightning information, the public should also make reference to the Thunderstorm Warning issued by the Observatory as well as the radar imageries and rainfall distribution map on the Observatorys Website, so as to gain a comprehensive appreciation of the thunderstorm situation.

In early 2005, the Observatory set up a lightning location network in cooperation with the Guangdong Meteorological Bureau and Macao Meteorological and Geophysical Bureau. The network consists of five sensors installed at Chung Hom Kok, Tsim Bei Tsui, Sha Tau Kok, Sanshui in Guangdong and Taipa in Macao respectively (Figure 4). The lightning location is calculated using the time of arrival and direction of the electromagnetic waves generated by the lightning discharges as detected by the network sensors. The network monitors lightning activities over the Pearl River Estuary round the clock.

The new lightning information serves as a supplement to the Thunderstorm Warning to alert the public to the potential threat of severe weather conditions in various parts of the territory to enable them to take necessary precautions. It also facilitates planning for outdoor activities such as hiking, water sports and paragliding.

Special users like construction companies and recreational facility operators will also benefit from the new service. The lightning location information can help them decide, based on their own level of acceptable risk, whether they would need to suspend their outdoor operations or activities. Customized lightning services will be provided on a cost-recovery basis to special clients through a dedicated webpage. Automatic audio and visual alarms will be triggered when lightning strikes occur within an area of interest centred at the client's pre-defined location. Those interested in the customized service are welcome to contact Mr. Julian Tang of the Hong Kong Observatory at 2926 8376 for details.

In the past 15 years, 35 persons have been struck by lightning in Hong Kong, of which six died. The public should be on the alert during thunderstorms. People engaging in outdoor activities should seek shelter in buildings when thunderstorms are affecting or expected to affect the area concerned. Do not stand on hill tops and keep away from conductive objects, trees or masts. Thunderstorms are often accompanied by squalls or violent gusts. People should take precautions against violent gusts and beware of flying debris and falling objects. Drivers using highways and flyovers should reduce speed and beware of violent gusts. Operators of small boats should take precautions to prevent their boats for capsizing due the approaching squalls or waterspouts. For more details on the Thunderstorm Warning, precautionary measures and lightning location information, please refer to the latest pamphlet on thunderstorm warning which is available at the website http://www.weather.gov.hk/wservice/warning/thunder.htm.

Figure 1.  Interactive graphical display of lightning location information over the Pearl River Estuary

Figure 2.  Delineation of four regions over Hong Kong for dissemination of regional lightning location information

Figure 3.  Automatic audio and visual alarms will be triggered when thunderstorms come within the region selected by the user

Figure 4.  Locations of lightning sensor stations