The remote effect of Typhoon Megi (2010) on the heavy rainfall over Northeastern Taiwan
Journal
Monthly Weather Review
Journal Volume
144
Journal Issue
9
Pages
3109-3131
Date Issued
2016
Author(s)
Chen, T.-C.
Abstract
The goal of this work is to improve understanding of the mechanisms leading to a heavy rainfall event under the combined influences of the outer circulation of Typhoon Megi (2010), the Asian monsoon, and the topography of Taiwan. Megi is a case featuring high forecast uncertainty associated with its sudden recurvature, along with remote heavy rainfall over northeastern Taiwan (especially at Yilan) and its adjacent seas during 19-23 October 2010. An ensemble simulation is conducted, and characteristic ensemble members are separated into subgroups based on either track accuracy or rainfall forecast skill. Comparisons between different subgroups are made to investigate favorable processes for precipitation and how the differences between these subgroups affect the rainfall simulation. Several mechanisms leading to this remote rainfall event are shown. The northward transport of water vapor by Megi's outer circulation provides a moisture-laden environment over the coastal area of eastern Taiwan. Meanwhile, the outer circulation of Megi (with high θe) encounters the northeasterly monsoon (with low θe), and strong vertical motion is triggered through isentropic lifting in association with low-level frontogenesis over the ocean northeast of Yilan. Most importantly, the northeasterly flow advects the moisture inland to the steep mountains in south-southwestern Yilan, where strong orographic lifting further induces torrential rainfall. In addition, the analyses further attribute the uncertainty in simulating Megi's remote rainfall to several factors, including variations of storm track, strength and extension of the northeasterly monsoon, and, above all, the impinging angle of the upstream flow on the topography. © 2016 American Meteorological Society.
Subjects
Atm/Ocean Structure/ Phenomena; Ensembles; Hurricanes/typhoons; Models and modeling; Numerical analysis/modeling; Rainfall
Other Subjects
Atmospheric thermodynamics; Hurricanes; Moisture; Uncertainty analysis; Weather forecasting; Ensemble simulation; Ensembles; Forecast uncertainty; Hurricanes/typhoons; Northeastern Taiwan; Numerical analysis/modeling; Rainfall simulations; Torrential rainfalls; Rain; atmospheric modeling; ensemble forecasting; hurricane; numerical model; precipitation intensity; typhoon; Taiwan; Yilan [Taiwan]
Type
journal article