Rethink on forecast focus of a torrential rainfall event at Jianghuai region

Abstract

Jianghuai region was hit by a torrential rainfall event on 18th-19th July, 2020. Numerical prediction models from ECMWF(hereinafter as EC model), East China Regional Meteorological Center/CMA(hereinafter as Huadong model), National Meteorological Center/CMA (3km resolution, hereinafter as G3 model) all present obvious northerly-offset in heavy rainfall area forecasts, and with weaker rainfall amounts as well. After detailed verification and analysis on models' wind fields and precipitation forecasts, it is founded that the performance of a model's synoptic situation forecasts are closely related to the model's precipitation forecast in most of times, especially for middle and low level wind fields which are easily affected by the model's precipitation latent heating process and thus would present wrong revision instruction to duty forecasters. Comparatively speaking, a model's forecast on high-level wind field is likely not affected by the model's precipitation latent heating process, which could be a reference deserving more attention during synoptic analysis. Furthermore, for a torrential rainfall caused by propagation of meso-or smaller scale weather systems, regional numerical model with higher resolution would be a better reference for forecast decision during similar heavy rainfall events.

Keywords

• torrential rainfall
• numerical model
• forecast focus
• high-level wind field