Subseasonal Weather Outlook and Review

1.1 In the first half of October 2019, the prevailing winds over the northern ASEAN region blew mainly from the northeast or east, and the prevailing winds over the southern ASEAN region were generally from the southeast or east. Winds were weaker over the equatorial areas. During this period, anomalously strong northeasterly or southeasterly winds prevailed over the ASEAN region.

Figure 1 5000 ft average winds (left) and anomalies (right) for 1 – 15 Oct 2019 (Source: JMA)

1.2 Drier-than-normal conditions were experienced in parts of the Mekong sub-region, including southern parts of Lao PDR, Viet Nam and Thailand, and much of Cambodia. In the southern ASEAN region, the presence of the monsoon rainband along the equatorial region brought showers to northern Sumatra, Malaysia, Singapore and some parts of Kalimantan. However, drier conditions persisted over southern Sumatra, southern and western Kalimantan and Java.

1.3 The daily average rainfall and the percentage of average rainfall for the first fortnight of October 2019 are shown in Figures 2 and 3 respectively.

1.4 Over the tropical Pacific Ocean, El Niño – Southern Oscillation (ENSO) remained neutral. In the Indian Ocean, the positive Indian Ocean Dipole (IOD) remained strong in the first half of October 2019

1.1 In the first half of October 2019, the prevailing winds over the northern ASEAN region blew mainly from the northeast or east, and the prevailing winds over the southern ASEAN region were generally from the southeast or east. Winds were weaker over the equatorial areas. During this period, anomalously strong northeasterly or southeasterly winds prevailed over the ASEAN region.

Figure 1 5000 ft average winds (left) and anomalies (right) for 1 – 15 Oct 2019 (Source: JMA)

1.2 Drier-than-normal conditions were experienced in parts of the Mekong sub-region, including southern parts of Lao PDR, Viet Nam and Thailand, and much of Cambodia. In the southern ASEAN region, the presence of the monsoon rainband along the equatorial region brought showers to northern Sumatra, Malaysia, Singapore and some parts of Kalimantan. However, drier conditions persisted over southern Sumatra, southern and western Kalimantan and Java.

1.3 The daily average rainfall and the percentage of average rainfall for the first fortnight of October 2019 are shown in Figures 2 and 3 respectively.

1.4 Over the tropical Pacific Ocean, El Niño – Southern Oscillation (ENSO) remained neutral. In the Indian Ocean, the positive Indian Ocean Dipole (IOD) remained strong in the first half of October 2019