Fig. 4: Spatial distribution of mean sea level pressure (MSLP) and trajectories of the extratropical cyclone (ETC) and integrated vapor transport (IVT) center.

a–g correspond to the 202108 event, h–n to the 202007 event, and o–u to the 201009 event. The first row (a, h, o) presents MSLP from observational data at the time of the maximum hourly precipitation recorded at the surface stations. ERA5 reanalysis data is used for all observational panels. The second to fourth rows present the trajectories detected in both the observation and the model simulations. In the trajectory panels, the left column (b, d, f, i, k, m, p, r, t) presents results of simulations with spectral nudging, whereas the right column (c, e, g, j, l, n, q, s, u) presents results without spectral nudging. In the observational MSLP panels, the black rectangles indicate the area where the trajectory is detected in each case, and the green diamonds mark the local minima of MSLP within this area. In the trajectory panels, the black and gray lines represent the observed ETC and IVT center trajectories, respectively. The thick blue and orange lines indicate the ensemble mean trajectories of the ETC and IVT center, respectively. The thin blue and orange lines denote the trajectories of individual ensemble members. The green-bordered markers indicate the position of the ETC and IVT center at the time of maximum hourly precipitation observed. The values in parentheses in the legend display the distance between the observation and ensemble mean trajectories at the time of maximum hourly precipitation. The marker interval is 3-h for the 202108 and 202007 events and 1-h for the 201009 event.