Review of Regional Haze Situation for April 2024
1.1 In April 2024, the prevailing winds over areas near the Equator turned light and variable in direction as the monsoon rainband shifted northwards towards the Equator. This is characterised with the transition of the Northeast Monsoon to the inter-monsoon conditions. Over the northern ASEAN region, the prevailing winds over the Philippines blew mostly from the northeast or east. While the prevailing winds over the northern parts of the Mekong sub-region were light and variable in direction, the prevailing winds over the rest of the sub-region blew mostly from the south or southwest (Figure 1).
1.2 Although some rainfall was observed over the northern, southeastern and central parts of the Mekong sub-region as well as the southern parts of the Philippines on a few days, dry conditions persisted over the northern ASEAN region on most days of the review period. The southern ASEAN region experienced wet weather on most days of the outlook period, except for the eastern parts of Borneo and the northern parts of Peninsular Malaysia and Sumatra where conditions were drier (Figure 1).
1.3 During the review period, the hotspot counts over the Mekong sub-region in April 2024 were largely higher or comparable to recent years (Figure 2). Over the southern ASEAN region, hotspot counts for Kalimantan and Malaysia in April 2024 were higher compared to previous years, but still relatively low compared to during the dry season. Elsewhere in the region, the hotspot counts were comparable to previous years (Figure 3).
1.4 In April 2024, scattered to widespread hotspots continued to be detected in the Mekong sub-region, with more intense and persistent clusters of hotspots in Lao PDR, various parts of Myanmar, northern Thailand and the northeastern parts of Cambodia (Figure 4 and 5). During most days of the review period, widespread moderate to dense transboundary smoke haze was observed to cover the eastern parts of Myanmar, northern and central parts of Thailand, and the northern parts of Lao PDR and Viet Nam (Figure 6 and 7). Moderate to dense smoke haze was also observed over other parts of Myanmar, Cambodia, and the eastern parts of Thailand (Figure 6). Moderate smoke plumes emanating from the hotspot clusters detected in the southern and central parts of Lao PDR were observed to drift northeastwards into the central parts of Viet Nam on a few days (Figure 6 and 8).
1.5 While the hotspot activity over the southern ASEAN region remained low, there were a few more intense and persistent hotspots detected in the eastern coastal areas of Peninsular Malaysia and the eastern parts of Kalimantan (Figure 4 and 5). Localised moderate smoke plumes (Figure 6, 9 and 10) were observed to emanate from these hotspots on some days.
