General weather patterns:
From 12 to 18 May 2020, there were some rainfall in the LMB. The weather outlook bulletins (3 months weather forecast: May-Jun-Jul) and maps issued by the Thailand Meteorology Department (TMD) were used to verify the weather condition in the LMB. They stated that from May-Jun-Jul 2020, the lowpressures of air mass cells are developed around the Mekong Region that cause some depressions and tropical cyclones, resulting summer thunderstorms and rain in this period. Moreover, coldly highpressure air masses from China will meet hot air masses already prevailing over LMB, resulting in abnormal rainfall in May-Jun.
According to the Asian Specialized Meteorological Centre (ASMC), the predicted below normal rainfall in the Mekong region is showed in May 2020. Figure 1 presented the weather map on 18 May 2020 and Figure 2 showed the predicted rainfall in May-Jun-Jul 2020.