Category Archives: Fortnightly Weather Outlook

Subseasonal Weather Outlook (1 – 15 September 2019)

Issued 2 September 2019
Valid for weeks 1 and 2: 1 September – 15 September

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

With the Indian Ocean Dipole (IOD) expected to remain in the positive phase, drier-than-usual conditions are forecast to persist over many parts of the southern ASEAN region, including Sumatra, Kalimantan and the Java Sea areas.

For the northern ASEAN region, above-average rainfall is forecast over the central and southern parts of the Mekong sub-region, as well as over the Philippines in Week 1.

During the first fortnight of September 2019, warmer conditions are expected over much of equatorial region.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 – 31 August 2019)

Issued 18 August 2019
Valid for weeks 3 and 4: 16 August – 31 August

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the northern ASEAN region, the third week of August 2019 is expected to be drier-than-usual except for the northern parts of the Mekong sub-region. In the last week of the month, near-average rainfall is expected for the region. In the southern ASEAN region, drier-than-usual conditions are forecast over Singapore, southern Peninsular Malaysia and many areas in Indonesia during the fortnight. The drier conditions in the southern ASEAN region can be partly attributed to the influence of the Indian Ocean Dipole (IOD) in the positive phase.

During the second fortnight of August 2019, warmer conditions are expected over many parts of the ASEAN region.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (1 – 15 August 2019)

Issued 1 August 2019
Valid for weeks 1 and 2: 1 August – 15 August

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the first fortnight of August 2019, above-average rainfall is predicted over northern Philippines, Viet Nam, parts of Myanmar and southern Thailand. With the Indian Ocean Dipole (IOD) predicted to remain in its positive phase, the southern ASEAN region and southern parts of the Philippines may experience drier-than-usual conditions.

In terms of temperature, warmer-than-average conditions can be expected over the equatorial ASEAN region and the inland areas of Thailand.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 – 31 July 2019)

Issued 12 July 2019
Valid for weeks 3 and 4: 16 July – 31 July

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the second fortnight of July 2019, wetter-than-average conditions can be expected over southern half of the northern ASEAN region, including the northern half of the Philippines. In the first week of this fortnight, warmer-than-average conditions are predicted over Myanmar and Thailand as well as over Lao PDR. Drier-than-average conditions are expected over the southern ASEAN region except for northern Sumatra and Peninsula Malaysia where average rainfall are predicted.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (1 – 15 July 2019)

Issued 2 July 2019
Valid for weeks 1 and 2: 1 July – 15 July

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the first fortnight of July 2019, drier-than-average conditions are expected over parts of the southern ASEAN region, including the southern parts of Sumatra and Kalimantan, and Java. Wetter-than-average conditions may develop over parts of eastern Maritime Continent and eastern Mekong sub-region in Week 1.

Warmer-than-average conditions present over the inland parts of the northern ASEAN region are expected to ease.

There is currently no significant Madden-Julian Oscillation (MJO) signal present. For the first fortnight of July 2019, there are no consistent signs of an MJO re-developing.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (1 – 15 June 2019)

Issued 3 June 2019
Valid for weeks 1 and 2: 3 June – 15 June

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the first half of June 2019, drier than average conditions are expected to persist over Myanmar.

For the rest of the northern ASEAN region, the prevailing drier than average conditions are likely to ease.

During the forecast period, the MJO that is currently active in the western hemisphere and Africa is forecast to propagate eastwards over the Indian Ocean. The presence of the MJO in Week 1 may bring wetter than average conditions over parts of the equatorial ASEAN region, including Sumatra, southern Peninsular Malaysia and south-western Borneo. However, drier than average conditions conditions can be expected over the areas surrounding Java Sea and Banda Sea.

Warm conditions are expected to continue over most of the northern ASEAN region.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 May – 31 May 2019)

Issued 15 May 2019
Valid for weeks 3 and 4: 16 May – 31 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the second half of May, drier-than-usual conditions are expected to persist in Myanmar, the southern Philippines, as well as northern and central Thailand. By the second week of the fortnight, the drier conditions are expected to extend over most parts of the northern ASEAN region.

In the southern ASEAN region, wetter-than-usual conditions are expected to develop over parts of Peninsular Malaysia, Sumatra and West Kalimantan towards the middle of the fortnight, and subsequently ease in the last week of May. The wetter conditions are associated with the Madden-Julian Oscillation (MJO), which is predicted to propagate eastwards through Phase 7 and Phase 8, and into Phase 1.

Most parts of the northern ASEAN region are expected to experience warmer-than-average conditions in the coming fortnight.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (1 May – 15 May 2019)

Issued 1 May 2019
Valid for weeks 1 and 2: 1 May – 15 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

May lies within the inter-monsoon period where prevailing winds over the Southeast Asia region are typically light and variable in direction. During this period, the monsoon rain band lies over the equatorial region and usually brings rainy weather over most parts of the Southeast Asia region.

In the coming fortnight, drier-than-usual conditions are expected to persist over parts of the Mekong sub-region, particularly over Myanmar. Meanwhile, wetter-than-usual conditions are forecast over the southwestern Maritime Continent, including the Java region. This is associated with the passage of Madden-Julian Oscillation (MJO) through the western Maritime Continent in Week 1. In the eastern Maritime Continent, drier-than-usual conditions are forecast to develop north of the equator in Week 1, spreading to the south of the equator in Week 2.

Warm conditions are expected to persist over most of the northern ASEAN region, as well as Peninsular Malaysia and Singapore.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 Apr – 30 Apr 2019)

Issued 12 Apr 2019
Valid for weeks 3 and 4: 16 Apr – 30 Apr

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the third week of April 2019, drier-than-usual conditions are expected to develop over parts of the Mekong sub-region, as well as over Malaysia and the Philippines. In the last week of the month, wetter-than-usual conditions are expected to develop over parts of Indonesia, with a possible development of Madden-Julian Oscillation (MJO) over the Indian Ocean. Most models predict the MJO to propagate slowly towards the east into the western Maritime Continent before weakening.

Warm conditions are expected to persist over the Mekong sub-region, as well as the northern part of Peninsular Malaysia.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.