A Decade after Typhoon Morakot (2009): What Have We Learned about Its Physics and Predictability?

Chung Chieh Wang*, Hung Chi Kuo, Yu Han Chen, Shin Hau Chen, Kazuhisa Tsuboki

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

3 Citations (Scopus)

Abstract

Typhoon Morakot struck Taiwan during 7–9 August 2009 and became the deadliest tropical cyclone (TC) in five decades by producing up to 2635 mm of rain in 48 h, breaking the world record. The extreme rainfall of Morakot resulted from the strong interaction among several favorable factors that occurred simultaneously. These factors from large scale to small scale include the following: 1) weak environmental steering flow linked to the evolution of the monsoon gyre and consequently slow TC motion; 2) a strong moisture surge due to low-level southwesterly flow; 3) asymmetric rainfall and latent heating near southern Taiwan to further reduce the TC’s forward motion as its center began moving away from Taiwan; 4) enhanced rainfall due to steep topography; 5) atypical structure with a weak inner core, enhancing its suscepti-bility to the latent heating effect; and 6) cell merger and back building inside the rainbands associated with the interaction between the low-level jet and convective updrafts. From a forecasting standpoint, the present-day convective-permitting or cloud-resolving regional models are capable of short-range predictions of the Morakot event starting from 6 August. At longer ranges beyond 3 days, larger uncertainty exists in the track forecast and an ensemble approach is necessary. Due to the large computational demand at the required high resolution, the time-lagged strategy is shown to be a feasible option to produce useful information on rainfall probabilities of the event.

Original languageEnglish
Pages (from-to)2161-2181
Number of pages21
JournalWeather and Forecasting
Volume37
Issue number12
DOIs
Publication statusPublished - 2022 Dec

Keywords

  • Extreme events
  • Hurricanes/typhoons
  • Mesoscale forecasting
  • Monsoons
  • Numerical weather prediction/forecasting
  • Rainfall

ASJC Scopus subject areas

  • Atmospheric Science

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