Abstract: Under the heavy rain criterion (MPV10), which are deduced from developing theory of slantwise vorticity, the several examples of landing typhoon with different tracks and structures have been interpreted on the heavy rain location. On the base of summing up the operational criterion, it is found that horizonal component of the wet potential vorticity MPV2 had better be replaced by the non-geostrophic component MPV2’ of it. Meanwhile, it is also mentioned that the top of typhoon inverted trough is the most active area of the typhoon interacting with westerly belt system, where the sub-synoptic scale and mesoscale disturbances appear frequently. Furthermore, it is shown that owing to rapid increasing of the vertical component of wet potential vorticity MPV1 and MPV2’, sudden heavy rain will probably happen in this area