Off-shore vortex and heavy rainfall events

Our colleagues reported the heavy rainfall events on 22-23, 28 November and 13 December in this blog. I noticed that a similar pattern of vortex with moist anomaly appeared to the west of Sumatera during these events (Figs. 1-3), which formed a few days before heavy rainfall events and propagated southeastward/eastward. The vortex formation seems to be related to variations in low-level winds to the west of Sumatera, and it moves eastward or westward, or rapidly collapses. The latest NICAM simulation says that the next formation and eastward propagation of vortex with moist anomaly likely occurs around 18 December (Fig. 4) (the simulation result varies day by day). Relationship between such local feature and heavy rainfall events is an interesting research topic. (T.N.)