Mesoscale processes for super heavy rainfall of Typhoon Morakot (2009) over Southern Taiwan

Within 100 h, a record-breaking rainfall, 2855 mm, was brought to Taiwan by Typhoon Morakot in August, 2009 resulting in devastating landslides and casualties. Analyses and simulations show that under favorable large-scale situations, this unprecedented precipitation was caused first by the convergence of the southerly component of the pre-existing strong southwesterly monsoonal flow and the northerly component of the typhoon circulation. Then the westerly component of southwesterly flow pushed the highly moist air eastward against the Central Mountain Range, and forced it to lift in the preferred area. The mesoscale processes in two stages were responsible for the unprecedented heavy rainfall total that accompanied this typhoon. Thus, understanding the dynamical interactions between the typhoon's circulation and monsoonal flow at different scales should enhance the forecasting capability in precipitation events brought by similar typhoons in the future.