Nowcasting thunderstorms for the 2008 sumer olympics

A Forecast Demonstration Project (B08FDP) is planned to take place during the summer of 2008 that will include the period of the summer Olympic Games in Beijing China. This demonstration is sanctioned by the World Meteorological Organization, World Weather Research Program. The demonstration will include state-of-the-art forecast systems from Beijing, Hong Kong, Australia, Canada and the United States. The focus will be on forecasting convective storms for the nowcasting time period (0-6 hours).

There will be a particularly rich data set available within the selected forecast area (500 by 500 km) centered on Beijing. This includes 4 Doppler radars, soundings at 6 hour intervals from 5 sites, 136 automated weather stations and 30 GPS receivers. During August the frequency of thunderstorms days in the metropolitan area of Beijing is over 25%, for an area within approximately 150 km of Beijing the frequency is greater 50%.

The metropolitan area of Beijing is on a flat plain located at the foot of a mountain range, Yan Shan Mountain, that extends west and north of the city. Beijing is at an altitude of only 30 m and is open to the south and east to the influx of very warm moist air. Significant forecast challenges present themselves in the vicinity of Beijing in response to this very humid air impinging on the nearby mountains. Thunderstorms frequently initiate over the mountains and move to the southeast. Sometimes these storms dissipate on reaching the foothills and other times grow and organize into major squall lines. A variety of boundary layer convergence lines frequent the plains and play a significant role in storm initiation and evolution. Beijing also appears to trigger thunderstorms. Examples of thunderstorm initiation and evolution are shown for a variety of forecasting challenges that will likely occur during the B08FDP. These examples are based on the Beijing S-band radar which was commissioned in summer 2006. This radar like NEXRAD routinely observes clear-air insect return to ranges of 100-150 km.

Statistical results of radar climatology based on Beijing local data from a C-band radar and surface observations are also presented. These results can help to enhance and improve nowcasting of convective storms in Beijing.