Quantitative weather forecasts at specific time and location
Although Hong Kong is a small city, it is characterized by its long coastline and complex topography. Weather conditions such as wind and temperature vary in different regions of the territory at times. For ease of transmission through the media, the usual weather forecast bulletin can only provide a general and territory-wide description of the weather forecast for the whole day, but cannot describe in full details the differences and changes in weather across different regions.
As the population becomes more and more widely distributed over Hong Kong, there is an increasing demand from the public for weather forecasts for different regions. To provide forecasts in finer spatial and temporal scales, the Observatory made efforts to enhance and optimize its numerical weather prediction model. After years of research, the resolution of the model has improved from several tens of kilometres to as fine as a few kilometres. This enables the provision of weather forecast for different regions in Hong Kong. To further enhance the forecast accuracy, the Observatory has developed post-processing techniques to continuously verify the forecast against actual observation of each region and fine-tune the subsequent forecasts automatically, ensuring that they are of acceptable accuracy for general use by the public.
Riding on the fruitful results of the research, the Observatory launched an innovative weather service - "Digital Weather Forecast" for the public in early 2010. It provides forecasts of hour-by-hour temperature, wind direction and speed one day ahead at a resolution of 10 kilometres in Hong Kong and in the neighbouring Pearl River Estuary. This is the first webpage developed in Hong Kong to provide fine-resolution and quantitative weather forecasts at specific time and location (Figure 1).
Figure 1: Digital temperature forecasts
In early 2011, the digital weather forecasts were extended from one day to three days with additional forecast on relative humidity. Furthermore, the public can easily select time series charts for any region, either through a map or by selecting the place, such as the name of a country park, peak, beach or tourist attraction (Figure 2).
Figure 2: Digital temperature forecasts at user selected location
The service has proved to be very useful for the public to appreciate the detailed changes in weather situation in the next three days, enabling them to plan ahead their activities. It is also of considerable value to weather-sensitive business like container terminals and power companies to better allocate and utilize their resources. Commendations were received after the launch of the service, for example, rating it a good service of high practical value, praising its usefulness in planning outdoor activities and choosing suitable clothing. The webpage won the Certificate of Merit of the Best Lifestyle (Green, Healthy & Creative Living) Award in the Hong Kong Information and Communication Technology Award 2011 (Figure 3).
Figure 3: The Director of the Hong Kong Observatory, C.M. Shun (2nd right)
and the development team of the digital weather forecast service in the
presentation ceremony of the Hong Kong Information and
Communication Technology Award 2011
Another new webpage "Weather Information for Hiking and Mountaineering" just launched this October integrated the digital weather forecasts with hiking routes and real-time weather information, enabling the hikers to better plan their hiking and mountaineering activities. To meet the needs of the public, the Observatory will continue to enhance the digital weather forecast webpage by adding more weather elements and exploring the integration of digital weather forecast with positioning technology, so as to provide hourly and location-specific weather forecasts for users with mobile devices.
LS Lee and YS Li
 "Digital Weather Forecast" http://www.hko.gov.hk/dfs/indexe.htm
 "Weather Information for Hiking and Mountaineering" webpage: http://www.weather.gov.hk/sports/hiking_e.html
 林日榮、李月嬋、陳世倜及葉曉峰：應用「模式輸出統計」校正數碼氣溫預報，第二十五屆粵港澳氣象科技研討會，香港，2011 年1 月26-28日 (Chinese only) (http://www.weather.gov.hk/publica/reprint/r948.pdf)
 Wong, W. K., 2010: Development of Operational Rapid Update Non-hydrostatic NWP and Data Assimilation Systems in the Hong Kong Observatory, The 3rd International Workshop on Prevention and Mitigation of Meteorological Disasters in Southeast Asia, 1-4, March 2010, Beppu, Japan.(http://www.hko.gov.hk/publica/reprint/r882.pdf)