The Column: Monthly Disaster Review and Outlook: Volume 85, September 2023

GENERAL REVIEW OF SEPTEMBER 2023

For the month of September 2023, a total of 111 disasters were reported. The number of reported occurrences was 42.49% less than the number of reported disasters in September of the last year. The ASEAN Member States affected for September 2023 were Cambodia, Indonesia, Myanmar, Philippines, Thailand, and Viet Nam. Most of the disasters (54.95%) occurred in Indonesia and accounted for 43.6% of the affected persons (around 670K persons), the highest number of affected persons for this reporting period. The share of the disaster-affected people for the other ASEAN Member States are as follows: (1) Indonesia – 43.62%, (2) Philippines – 28.07%, (3) Thailand – 14.16%, (4) Cambodia – 13.13%, (5) Viet Nam – 0.42%, (6) Myanmar – 0.39%, and (7) Malaysia – 0.21%. September 2023 saw disasters affecting 223 per 100,000 people* and displacing 5 per 100,000 people* in the region, which was significantly lower (36% and 58%, respectively) compared to the previous month.

Out of the total reported disasters in September 2023, 48.65% was flood which mostly occurred in the northern hemisphere and consistently the most recorded type of disaster for the month of September of the previous year and September on a five-year average (2018-2022). However, due to the effects of El Niño, drought ranked as the second most reported disaster (29.73%), particularly in the southern parts of the equatorial line (Indonesia) for September 2023. The reported number of droughts (33) was 33x more than the reported drought in September of the previous year (1) and 15.5x more than the five-year (2018-2022) average for drought in September (2). While the reported disasters in the region for September 2023 in comparison with the historical data (average for September 2018-2022) indicates 1.5x more reported disasters, there were 2.7x less affected people, 4.2x less people internally displaced, 1.6x less houses affected to some extent, 13.4x less lives lost, and 281x less people suffering injuries.

GEOPHYSICAL CONDITION FOR SEPTEMBER 2023

Geophysically, 22 significant earthquakes (Magnitude ≥ 5.0) were reported by Indonesia’s Badan Meteorologi, Klimatologi dan Geofisika (BMKG) and the Philippine Institute for Volcanology and Seismology (PHIVOLCS) for the period of September 2023.

Mounts Ibu (Alert Level II), Semeru (Alert Level III), Dukono (Alert Level II), Ili Lewotolok (Alert Level II) in Indonesia and Mayon (Alert Level 3), Taal (Alert Level 1), and Kanlaon (Alert Level 1) in the Philippines were reportedly tectonically active (erupting lava or releasing gas or generating seismic activity) throughout the month of September 2023.

As of 1 October, PHIVOLCS maintained the Mayon Volcano at Alert Level 3 (Increased Tendency Towards Hazardous Eruption). According to PHIVOLCS, there have been volcanic earthquakes, rockfall events, and pyroclastic density current events still within the 4-km radius from the crater. Volcanic sulfur dioxide (SO2) emissions averaged 1392 tonnes/day for September 2023 and hazardous eruption within weeks could still be possible. According to NDRRMC’s report on 11 October, a total of 9,876 families or 38,396 persons were affected. Of which, 52 families (195 persons) remain displaced inside 1 evacuation centre. The NDRRMC with other relevant-agencies/stakeholders have provided 7.9M USD worth of assistance to those affected.

*computed based on 2023 population data from worldometers.com

ANALYSIS

According to the ASEAN Specialised Meteorological Centre (ASMC), the Southwest monsoon conditions persisted over the region in September 2023. ASMC noted that the prevailing low-level winds blew mainly from the southeast from the south of the equatorial line and turned to blow from the southwest or west over areas north of the Equator Dry conditions prevailed over many parts of southern ASEAN region as the area remained under the traditional dry season. Isolated showers were recorded over parts of northern Sumatra, Malayasia, and northeastern Kalimantan. Over the northern ASEAN region, the weather was generally wet as the traditional wet season prevailed. The average daily rainfall and mean winds in the region for September 2023 are illustrated in Figure 1. Moderate to heavy rainfall concentration over the northern and northeastern parts of Thailand and north, northwestern, and central provinces of Cambodia, especially those in low-lying areas and near river systems, may have contributed to the flooding events that affected 69K families in these areas.

SEASONAL OUTLOOK

According to the ASEAN Specialised Meteorological Centre (ASMC), the Southwest Monsoon conditions that prevailed in September 2023 are expected to continue into the month of October. It is expected that during this period, the prevailing winds over the ASEAN region are blowing mostly from the southeast or southwest. Northern ASEAN region may experience rainy weather while drier conditions may be expected in the southern part of the region.
Towards the end of October 2023, the weak or variable winds may be experienced as the inter-monsoon period sets in. Meanwhile, increased shower activities over most of the equatorial region may be expected as the monsoon rain-band migrates southwards towards the equator.

For the next 3 months, (October-November-December 2023), an increased chance of below-normal rainfall is predicted for most of the southern ASEAN region, extending to include the Philippines. Meanwhile, an increased chance of above-normal rainfall is also predicted over parts of Mainland Southeast Asia over this period. El Niño conditions are predicted to strengthen over the next few months and persist at least until the start of 2024 and a positive Indian Ocean Dipole (IOD) is now present and likely to persist during October-November. El Niño and positive IODs may bring drier conditions to most parts of the region. Above-normal temperature is predicted for most of the ASEAN region for October-November-December 2023.