The self-developed global/regional assimilation and prediction system-regional ensemble prediction system (GRAPES-REPS) was put into operation in 2014 in China. In order to deeply understand the precipitation ensemble forecast ability of this system and conveniently apply the precipitation probability forecast, in this paper, the 24 h accumulated precipitation with different magnitudes forecasted by GRAPES-REPS at different lead time within 72 hours is evaluated by using statistical analysis and case analysis taking three continuous precipitation processes in southern China from mid-May to late June 2017 for example. The results are as follows: (1) The ensemble mean forecast of GRAPES-REPS has obvious advantage for light rain and moderate rain. The advantage decreases gradually with the increase of precipitation magnitude and no advantage appears for rainstorm. The ensemble mean forecast is close to the observation for light rain, while it has a tendency of null (missing) forecast for moderate rain (rainstorm) or heavy rain at a longer lead time. (2) The optimal members include control forecast and two perturbation forecasts that use a combination of MRF boundary layer scheme and KF-eta cumulus convection scheme, which is different to the other members. (3) The spread of precipitation ensemble forecasts is insufficient overall, especially at 0-24 h forecast lead time with the U-shaped Talagrand distribution and the higher (lower) forecast probability for small- (large-) magnitude precipitation. The spread increases obviously with the increase of forecast lead time, and the Talagrand distribution is gradually close to the expected-probability distribution. (4) The ensemble forecasts do have a reference value for precipitation with different magnitudes at every forecast lead time, with the probability forecast of heavy rain and rainstorm being better than that of light rain and moderate rain. (5) The ensemble gives a better forecast for precipitation pattern with different magnitudes as a whole, especially it has an ability of probability forecast for the warm-sector rainstorms in the central and southern Guangdong Province, which is missing in the forecasts of National Meteorological Observatory.

There was a rare rainstorm weather process in the North of China on July 21，2012，which led to the most severe flooding disasters．The weather system of the process was the cold front with the upper trough，but such a system would not lead to more than 200 mm rainfall in 24 hours according to the statistical results of the last decade ( 2000 － 2011) ． After the precipitation in Beijing ，the torrential rain occurred in the middle of Hebei Province ( Langfang and the northeast of Baoding) ，where heavy rainfall occurred relatively less in the past． Thus，some reasons of the torrential rainfall in Hebei and the forecasting focus were analyzed in the article，based on the conventional observation data，reanalysis data from NCEP at 1° × 1° spatial resolution，regional automatic meteorological observation data and Doppler weather radar data． The comparative study of weather patterns，physics conditions and meso － and micro－ scale systems were carried out with another rainstorm process which occurred on the 24th July 2011． The results show that there were great differences between two weather processes in extreme value of precipitation and rainfall area，although their precipitation efficiency and meso － and micro － scale systems which directly resulted  in two precipitation processes were similar under the same synoptic scale circulation situation ( low － cold front type) ． The extreme precipitation in 7． 21 process had a closely relation to strong moisture transport，intense dynamic condition and high precipitation efficiency，but the train effect for 6 hours was the leading cause of the heavy rainfall． The configuration of low frontal zone of se and low － level jet on the south of shear line led to the train effect in the middle of Hebei Province，which was concluded as a forecast point of the kind heavy rain events． And，the ground mesoscale convergence line ahead of the cold front was a key point for accurately forecasting heavy rainfall area，which was better than based on the southeast quadrant of the lower vortex，because strong precipitation occurred along with lines．

By using meteorological observation data from eight weather stations in Southwest Guizhou and Micpas data and NCEP reanalysis data in recent five years， the spatial and temporal distribution of fog weather in Southwest Guizhou was analyzed in this paper． The results show that the main synoptic patterns resulted to fog weather here were the westerly flow in front of the southern trough and the northwest flow behind the upper trough，and physical quantity fields analysis indicated that the low － level air was wet when frontal fog appeared，and the atmosphere structure was relatively stable，there was a temperature inversion layer in lower level，and a weak upward motion nearby frontal area．