A four-dimensional variational Doppler radar analysis system (VDRAS) is used to analyze the three dimensional wind fields and microphysical fields of a rainstorm case in Beijing on July 30,2008.After discussing some key points in short-term and nowcasting forecast such as the weakening and dissipation of the eastern echo as well as heavy rain area and the turning of echo,some preliminary conclusions were obtained:1) 12-24 minutes before the weakening and dissipation of the eastern echo,a hollow structure (even negative point) appeared in corresponding analyzed perturbation temperature positive region at the height of 4.7 km,and at the same time ascending and descending flow separated in the same region at the height of 1.7 km.2) If the duration of the analyzed perturbation temperature in some regions was higher than that in other regions for 2 hours or longer,or the perturbation temperature increased rapidly in few minutes and reached the extreme value (above 2℃),there was a good chance that heavy rain would occur in 1-2 hours in this region.3) The turning of the echo was conducted by the western air flow of anticyclone style circulation flow at the height of 1.7 km.A convergence ascending flow was horizontally transported from western region to Miyun and Pinggu in the eastern region,and then a divergence descending flow of anticyclone type came into being.The moving of radar echo was affected by the air flow and this flow occurred about 1 hour before the echo turning.