Abstract
It is very important for appropriate dam operation and disaster prevention to predict severe rainfall in mountainous region. For last several years, we have developed rainfall prediction system for the Kurobe-Valley, which is consist of steep mountains and valleys. The system has been already installed and used at the dam administration offices. The system had a weak point in terms of the rainfall prediction especially at the beginning of rainfall event. In this paper, we reveal that precipitable water vapor is related with rainfall event, and propose a new index which is applicable for the signal of the beginning of rainfall event for real-time estimation.
