Analysis of Short-Term Nowcasting Warning Indicators for Heavy Rainfall Based on Vertical Profiling Data: A Preliminary Methodological Framework from a Case Study in Qingdao

Based on wind profiler radar and ground-based microwave radiometer observations in Qingdao, a rainstorm event that occurred on 15–16 July 2025 is analyzed to extract the different characteristics of dynamic, moisture and thermal conditions between coastal (Qingdao) and inland (Pingdu) stations. Then, a preliminary short-term nowcasting warning indicator system is proposed. The results show that Qingdao station exhibited explosive precipitation characteristics triggered by cold-air intrusion, while Pingdu station exhibited persistent precipitation characteristics associated with warm-sector convective development. A high-level accumulation of the low-level jet (LLJ) index was a prerequisite for precipitation, and its enhancement and core lowering served as precursors to rainfall onset. The turning points of peak integrated water vapor (IWV) and integrated liquid water (ILW) content, as well as the inflection points where brightness temperature shifts from rising to falling, have clear warning significance for heavy rainfall. A three-level graded warning indicator system can provide warning information 30 min to 2 h before precipitation onset. It should be emphasized that this study is based on a single precipitation event and the proposed warning indicators constitute a preliminary methodological framework. Further validation using multiple historical cases and rigorous statistical evaluation is required before operational implementation.