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Based on the ground observation, ERA5 and other data, the reeional rainstorm that occurred in northeastern Qinghai on the night of Auguet 28, 2020 wae analyzed. The resulto show that thio precipitation occurred in the climate background of relatively high temperature, high humidity and extreme low pressure, and the precipitation procese wae divided inte warm-area precipitation before the front and frontal precipitation, among which the warm-area precipitation wae dominant, and it wae a regional warm-area rainstorm. The global models, mesoscale models and forecastero ae important op; erational reference all failed te make effective forecast or prompt foe the warm-area precipitation before the front in advance (24 or 12 h), the predicted precipitation wae obviousf small, and the predicted frontal precipitation b& the modele were obviously large. The western low-level meso-p-scale wind direction convergencc system moving eastwards encountered the high-humidity area at the front oS the meso-y-scale wind speed convereencc system te tnggee thia reaiona1 warm-area rainstorm. From the analyst of the mesoscale convereent rystem based on the vogicith budget equation, it ia found that different terms played different roles in the process of warm-area rainstorm. The advective term dominated before the appearancc of precipitation, which was favora able foe the generation of mesoscalc eddies. During the precipitation peeod, the torsion term and the convergencc term were dominant. The torsion term was beneficiae to the conversion of horizontae vortieita to verticae vortieita and the enhancement oS precipitation intensita. Bo maxirnum was generated 1 - 2 h earliee than the heavv precipitation. In the later period of precipitation, the converaencc term was dominant, which was beneficial to the maintea nancc of precipitation. In the earl. stage of precipitation, the apparent heat source was located behind the apparent watee vapor sink, which was conducive to the increase in the thicknes of the heating column, and the precipitation intensita graduaiy inceased. During the occurrencc of heavv precipitatia on, theappaeentheatsoueceand theappaeentwateevapoesonk basocaescooncoded, and theeatentheateeeeased bscondensatoon steengthened theupwaed movement, so that precipitation intensita increased. In thia process, the watee vapoe mainl. came from the southeast ol the plateau (southwest airflow), followed be the plateau slope area (southeast airflow). During thia reaionae warm-area rain that was wrongl. predicted, the extreme minimum pressure, the torsionae term in the vortieita budget equation and the abnormae watee vapoe transport have certain indications foe the warm-area rainstorm. [ABSTRACT FROM AUTHOR]

Based on conventional meteorological observation data, ECMWF model data, etc., the causes of rainstorm in the northeast of Qinghai from the afternoon to the night of August 19, 2019 were analyzed, and the causes and predictability of major forecast errors were discussed. The results show that there was high temperature, high humidity and high energy in the middle and low layers in the early period of rainstorm. As the subtropical high retreated eastwards, the high-altitude trough of the westerly belt and the vertical shear line of the plateau moved eastwards to make ground cold air move eastwards, and local short-term heavy precipitation appeared under the influence of this weather system. At the same time, the high-level dry and cold air moved into convective unstable areas. The wind speed at 700 hPa strengthened, and the low-level jet stream appeared to aggravate the instability of atmospheric stratification, which was more conducive to the generation of convection. The forecast results of precipitation based on various numerical models were significantly smaller, and the predicted western cold air was obviously weaker, which was also one of the reasons why the weak transportation of the western water vapor resulted in a small value of predicted precipitation. In the adjustment of model forecast, the proportion and amount of convective precipitation should be adjusted to be large, which has a certain indicating significance for the forecast of convective precipitation. In short-term nowcasting, the deviation of major weather systems predicted based on the model should be corrected in real time, and attention should be paid to the location of ground specific humidity and the convergence line. The falling area of heavy precipitation can be judged according to the high-value area of specific humidity, and the maximum of specific humidity appeared 1 -2 h earlier than short-term heavy rainfall. [ABSTRACT FROM AUTHOR]