A062-0011
High-impact weather events and their links to mesoscale convective systems over Southeast Asia

Wednesday, 9 December 2020
Poster
Rory Fitzpatrick1, Simon Peatman2, Cathryn Ellen Birch3, Juliane Schwendike3, Sam Hardy3 and Thorwald Hendrik Matthias Stein4, (1)University of Leeds, Leeds, LS2, United Kingdom, (2)University of Leeds, School of Earth and Environment, Leeds, LS2, United Kingdom, (3)University of Leeds, School of Earth and Environment, Leeds, United Kingdom, (4)University of Reading, Meteorology, Reading, RG6, United Kingdom
Abstract:
Recent years have seen high-impact weather events cause widespread damage and loss of life over Southeast Asia. Understanding the local and synoptic conditions which aid the organization and intensification of high-impact mesoscale convective systems (MCSs) is of pivotal interest to decision-makers across the region in order to prepare for such events.

An objective tracking method is used to identify MCSs from genesis to decay using Himawari satellite brightness temperature data. We then quantify the contributions of tracked MCSs to observed high-impact weather events related to high rainfall and strong wind gusts. The interaction between large-scale atmospheric drivers, such as the Madden-Julian Oscillation, equatorial waves, and other large-scale weather regimes, and their effects on storm-scale drivers of storm organization are evaluated for each season.

Over land regions, little spatial agreement is found in the timing of intense weather events across neighboring grid-points; however, greater levels of spatial homogeneity are evident over the Pacific Ocean. Seasonal differences in the frequency, level of organization, and impacts (such as precipitation rates) of MCSs are found across many countries in Southeast Asia. However, over the South China Sea, there is little seasonal difference in the observed population of MCSs in terms of their organization or intensity throughout the year.

The intensity of observed weather events is strongly associated with local atmospheric conditions, including ambient wind shear, low-level humidity, convective available potential energy, and low-level wind convergence. These storm-scale drivers are in-turn modulated by large-scale conditions. Through a meta-analysis of all identified systems over Southeast Asia, we summarize conditions most conducive to high-impact weather over the region, and present the dynamics through which intense storms develop in these conditions using case-studies of high-impact weather events.

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