Review of Regional Haze Situation for October 2023
1.1 The Southwest Monsoon gradually transitioned into inter-monsoon conditions from the end of October 2023. As the monsoon rainband moved towards the Equator, the prevailing winds weakened and turned light and variable over the equatorial regions (Figure 1). During the first week of October, Typhoon Koinu (Figure 9) brought about heavy rainfall and strong winds over parts of the northern Philippines.
1.2 Dry weather persisted over much of the southern ASEAN region for the first half of October, with moderate to dense haze observed mainly over southern and central Sumatra, as well as southern and central Kalimantan (Figure 6). Towards the end of October, there was an increase in showers over parts of southern Kalimantan and southern Sumatra, which helped to improve the hotpot and haze situation (Figure 1). On 24 October 2023, the ASMC Alert Level for the southern ASEAN region was downgraded to Alert Level 1 as the risk of transboundary haze subsided. Over the northern ASEAN region, wet weather prevailed, and the overall haze situation was subdued in the region (Figure 1).
1.3 Over the southern ASEAN region, the hotspot counts in October 2023 were mostly higher compared to previous years, especially over Sumatra and Kalimantan where there was a significant rise in hotspot activity with the highest count recorded in five years (Figure 2). Over the Mekong sub-region, the overall hotspot count in October 2023 was mostly comparable to or lower than in previous years (Figure 3).
1.4 In October, hotspot activities were persistent in parts of central and southern Sumatra, southern and central Kalimantan, as well as parts of the Lesser Sunda Islands and Sulawesi (Figure 4). The fire intensity was highest for parts of southern Sumatra and Kalimantan (Figure 5). Moderate to dense smoke haze was observed in central and southern Sumatra, as well as southern and eastern Kalimantan on many days this month (Figures 6, 7 and 8). Lighter smoke haze drifted under prevailing winds to affect parts of Peninsular Malaysia and Singapore in early October 2023.