Vol 86 – MONTHLY DISASTER REVIEW AND OUTLOOK

GENERAL REVIEW OF OCTOBER 2023

For the month of October 2023, a total of 77 disasters were reported in the ASEAN region. The number of reported occurrences was 2.8x less than the number of reported disasters in October of the last year. The ASEAN Member States affected for October 2023 were Indonesia, Malaysia, Myanmar, Philippines, and Viet Nam. Majority of the disaster (62.34%) occurred in Indonesia and accounted for 86.48% of the affected persons (about 320K persons) and 66.75% of affected houses (around 11.35K houses) for this reporting period. The share of the affected people for the ASEAN Member States are as follows: (1) Indonesia – 86.48%, (2) Viet Nam – 5.31%, (3) Philippines – 4.70%, (4) Myanmar – 3.29%, and (5) Malaysia – 0.23%. With the decrease in the number of significant disasters in October 2023, 54 per 100,000 people* were affected which was about 4x less than the number of affected persons last month. Meanwhile, about 3 per 100,000 people* in the region have been displaced, which was 1.6x less compared to the previous month.

Out of the total disasters in October 2023, flood accounted for the highest percentage of occurrence at 40.26%. Flood had been consistently the most recorded type of disaster in the region but the recorded floods for October 2023 is 1.9x less than the five-year average (2018-2022) for October and 4.9x less than the flood incidents in October of the last year. Wind disasters ranked second with 20% of the reported disasters in October 2023. The reported floods and wind disasters were generally attributed to continuous rains and strong winds associated with the monsoons and enhanced by two tropical cyclones (Tropical Cyclone KOINU and SANBA) that passed by the region and affected the Philippines and Viet Nam at the start and in the middle of October 2023. While floods had been the most recorded disaster for this period, drought, which accounted for 18.18% of recorded disasters in October 2023, had the most number of affected persons at 74.90% (about 277K persons) in Indonesia. The decreasing rainfall and water supply were associated with the effects of El Niño that had affected the region, particularly in the southern portions of the equatorial line. The reported droughts for this reporting period was 14x more than the five-year (2018-2022) average for the month of October. Overall, compared to the historical data (average for October 2018-2022), the available data on the disasters and associated impacts for the month of October 2023 indicates 1.19x less reported disasters, 9.4x less affected people, 5.9x less people internally displaced, 9.6x less houses affected to some extent, 8.5x less lives lost, and 27.8x less people suffering injuries.

GEOPHYSICAL CONDITION FOR OCTOBER 2023

Geophysically, 26 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 October 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 October 2023.

On 12 October 2023, PHIVOLCS released a notice of increased and continuous degassing activity from Taal Volcano with 9,762 tonnes/day of volcanic sulfur dioxide gas emission from Taal Main Crater. This was the highest recorded SO2 emission from Taal for the year 2023 at the time, which was 2.6x the average SO2 emission of 3,781 tonnes/day since September 2023. According to PHIVOLCS, the prevalence of Alert Level 1 indicated that Taal remained in abnormal condition and may cause sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfalls and lethal accumulations or expulsions of volcanic gas.

*computed based on 2023 population data from worldometers.com

ANALYSIS

According to the ASEAN Specialised Meteorological Centre (ASMC), the Southwest Monsoon gradually transitioned into inter-monsoon conditions from the end of October 2023. As monsoon rainband moved towards the equator, the prevailing winds weakened and turned light and variable over the equatorial regions as shown in Figure 1. In addition, Tropical Cyclone KOINU which tracked northeast to north of the Philippines brought about heavy rainfall and strong winds over the northern regions of the Philippines. Above-average to high rainfall also accumulated over the Central and Northern Central Regions of Viet Nam, which was attributed to Tropical Cyclone SANBA in the middle of October 2023 and brought about landslides and flooding in these areas. Towards the end of October, Tropical Cyclone HAMOON brought above average rainfall along the coastal areas of Rakhine Territory in Myanmar before making landfall in Bangladesh. Meanwhile, dry weather persisted over much of the southern ASEAN region for the first half of October, while an increase in showers over parts of southern Kalimantan and southern Sumatra occurred towards the end of October. Most of Java and Sulawesi in Indonesia have remained dry and these conditions had been associated with the drought disasters that had occurred and affected about 277K persons in these areas.

SEASONAL OUTLOOK

According to the ASEAN Specialised Meteorological Centre (ASMC), the Southwest Monsoon transitioned into the inter-monsoon period from the end of October 2023. Prevalence of the inter-monsoon conditions may be expected over the ASEAN regions in November, where the prevailing winds are light and variable in direction over most parts of the region. An increase in shower activities is also likely with the monsoon rainband located close to the equator. Gradual onset of the Northwest Monsoon can be expected from December, during which the prevailing winds over the ASEAN region blow predominantly from the northwest or northeast.

An increased chance of below-normal rainfall is predicted for November 2023 to January 2024 over the southern and eastern Maritime Continent. Meanwhile, the northwestern Maritime Continent is likely to have above-normal rainfall. The ocean indicators (Nino3.4 index) shows El Niño conditions with support from key indicators (cloudiness, trade wind). El Niño conditions are likely to persist until at least February to March 2024. ASMC notes the presence of a positive Indian Ocean Dipole (IOD) which is predicted to end by January to February 2024. Both El Niño and positive IOD tend to bring drier conditions to much of the region. For the period of November 2023 to January 2024, ASMC predicts above-normal temperature for most of the ASEAN region.

Note: The qualitative outlook is assessed for the region in general and based on the latest runs from models provided by the SEA RCC-Network LRF node. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Sources: ASEAN Disaster Information Network (ADINet), ASEAN Disaster Monitoring and Response System (DMRS), ASEAN Specialised Meteorological Centre (ASMC), Badan Nasional Penanggulangan Bencana (BNPB) – Indonesia, Agensi Pengurusan Bencana Negara (NADMA) – Malaysia, Department of Disaster Management (DDM) – Myanmar, National Disaster Risk Reduction and Management Council (NDRRMC) – Philippines, Department of Disaster Prevention and Mitigation (DDPM) – Thailand, Thai Meteorological Department (TMD) – TMD, Badan Meteorologi, Klimatologi dan Geofisika (BMKG) – Indonesia, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) – Indonesia, Philippine Institute for Volcanology and Seismology (PHIVOLCS) – Philippines, Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) – Philippines

Written by : Jasmine Alviar, Sadhu Zukhruf Janottama, Lawrence Anthony Dimailig