Category Archives: Fortnightly Weather Outlook

CR58

October 30, 2020

Subseasonal Weather Outlook (2 – 15 November 2020)

Issued 30 October 2020
First forecast week: 2 November – 8 November
Second forecast week: 9 November – 15 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are predicted over the western Maritime Continent and southern Mainland Southeast Asia next week (2 – 8 November), easing in the second week (9 – 15 November). Parts of this region may however, experience near-normal rainfall, particularly along eastern coasts of Sumatra and the Malay Peninsula.

Wetter conditions are predicted over northern Myanmar in the first week (2 – 8 November). Wetter conditions are also predicted over northern Philippines during this first week, possibly extending to the west in the second week (9 – 15 November), although the location and extent of these wetter conditions will depend on tropical cyclone development.

No significant regional temperatures anomalies are expected in Southeast Asia in the next fortnight (2 – 15 November).

A Madden-Julian Oscillation (MJO) signal is present over the Pacific (Phase 6). Most models predict the MJO to continue propagating eastwards, potentially strengthening over the Western Hemisphere and Africa (Phases 8 and 1) in the second week.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

October 16, 2020

Subseasonal Weather Outlook (19 October – 1 November 2020)

Issued 16 October 2020
First forecast week: 19 October – 25 October
Second forecast week: 26 October – 1 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over eastern Mainland Southeast Asia and the Philippines for the next two weeks (19 October – 1 November), although the location and intensity of these wetter conditions will depend on tropical cyclone evolution. Wetter conditions are also predicted over parts of Java and southern Sumatra next week (19 – 25 October).

In general, drier conditions are predicted over the western Maritime Continent next week (19 – 25 October), gradually easing in the second week (26 October – 1 November). Parts of this region may however, experience near-normal conditions, particularly along eastern coasts of Sumatra and the Malay Peninsula.

Warmer temperatures are predicted over much of the equatorial region and northern Myanmar in the next fortnight (19 October – 1 November). Cooler temperatures than usual for this time of year are predicted over parts of Mainland Southeast Asia (Viet Nam, Lao PDR, northern Thailand and Cambodia).

A moderate Madden-Julian Oscillation (MJO) signal appears to be developing over the eastern Maritime Continent. Most models predict the MJO to propagate eastwards over the Pacific, although weakening slightly due in part to the La Niña conditions present.

October 2, 2020

Subseasonal Weather Outlook (5 – 18 October 2020)

Issued 2 October 2020
First forecast week: 5 – 11 October
Second forecast week: 12 – 18 October

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over the eastern half of Southeast Asia for the next two weeks (5 – 18 October). During this time, models are also predicting wetter conditions for eastern Mainland Southeast Asia (Cambodia, Lao PDR, Viet Nam, and parts of Thailand), although the location of these wetter conditions will depend on tropical cyclone evolution. Wetter conditions are also expected over northern Sumatra in week 1 (5 – 11 October).

Warmer temperatures are predicted for the central and northern parts of Myanmar for the next two weeks. Warmer temperatures are also predicted to develop over the western Maritime Continent in week 2 (12 – 18 October).

A weak Madden-Julian Oscillation (MJO) signal was present over the Maritime Continent at the beginning of October (Phase 5). However, none of the models predict a coherent MJO signal to develop in the next two weeks.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

September 21, 2020

Subseasonal Weather Outlook (21 September – 4 October 2020)

Issued 21 September 2020
First forecast week: 21 September – 27 September
Second forecast week: 28 September – 4 October

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over the equatorial region in the first week (21 – 27 September), easing in most places except Papua in the second week (28 September – 4 October).

Warmer conditions are expected during the fortnight over most of Mainland Southeast Asia (except northern Myanmar), the Philippines and southern parts of Southeast Asia, with closer to normal temperatures in the equatorial region (corresponding to the wetter conditions in the rainfall outlook).

The previous Madden-Julian Oscillation (MJO) signal weakened after entering the Maritime Continent (Phase 4), just before the start of the forecast period. Most models predict this weak MJO signal to continue propagating across the Maritime Continent and over the Western Pacific.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

September 7, 2020

Subseasonal Weather Outlook (7 – 20 September 2020)

Issued 7 September 2020
First forecast week: 7 September – 13 September
Second forecast week: 14 September – 20 September

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the northern part of Southeast Asia, drier conditions are predicted to persist for the first week (7 – 13 September), before returning to normal in the second week (14 – 20 September). For the equatorial region, wetter conditions are predicted in the first week, gradually easing in most places the following week, except for southern Thailand, northern Borneo and northern Sulawesi.

Warmer conditions are expected during the fortnight over northern and southern parts of Southeast Asia, with closer to normal temperatures in the equatorial region (corresponding to the wetter conditions in the rainfall outlook).

At the start of September, a Madden-Julian Oscillation (MJO) signal was present in the Indian Ocean (Phase 3). Most models predict this MJO to decay by the start of the first week of the forecast.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

August 21, 2020

Subseasonal Weather Outlook (24 August – 6 September 2020)

Issued 21 August 2020
First forecast week: 24 August – 30 August
Second forecast week: 31 August – 6 September

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first week (24 – 30 August), wetter conditions are predicted around the equatorial region. The wetter conditions are expected to spread further southwards in the second week (31 August – 6 September). For the northern part of Southeast Asia, drier conditions are predicted for the fortnight, with higher likelihood in the first week.

Warmer conditions are expected during the fortnight over most parts of Southeast Asia except for the western Maritime Continent (parts of Peninsular Malaysia, Sumatra, and Borneo), corresponding to the rainfall outlook.

A Madden-Julian Oscillation (MJO) signal recently emerged in Western Hemisphere (Phase 8). Models predict the MJO to propagate eastwards towards Africa and the Indian Ocean during the fortnight.

August 8, 2020

Subseasonal Weather Outlook (10 – 23 August 2020)

Issued 8 August 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

During the fortnight (10 Aug – 23 Aug), wetter conditions are expected over southern Southeast Asia particularly over the near-equatorial region as highlighted in the rainfall map.

Warmer conditions are expected during the fortnight over the southern and western parts of Southeast Asia.

A Madden-Julian Oscillation (MJO) signal developed over the Indian Ocean in the past fortnight, propagated eastwards and is now in the western Maritime Continent. Most models predict the MJO to continue propagating eastwards but may weaken in the first week.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

July 27, 2020

Subseasonal Weather Outlook (27 July – 9 August 2020)

Issued 27 July 2020
First forecast week: 27 Jul – 2 Aug
Second forecast week: 3 Aug – 9 Aug

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first forecast week (27 Jul – 2 Aug), wetter conditions are expected over much of the equatorial region, as well as southern and eastern coastal regions of Mainland Southeast Asia and the Philippines.

In the second forecast week (3 Aug – 9 Aug), wetter conditions are expected over eastern Southeast Asia and over the southern and eastern regions of Mainland Southeast Asia as highlighted in the rainfall map.

Drier conditions are expected over southern parts of Southeast Asia (southern Sumatra and Java). In the second week, drier conditions are also expected to develop over the rest of Sumatra and the region covering Peninsular Malaysia and western Borneo.

Warmer conditions are expected over northern Southeast Asia, particularly in the first forecast week. In the second week, warmer conditions are expected to develop over the western equatorial region, in line with the drier conditions.

While there are some signs of a Madden-Julian Oscillation (MJO) signal in the western Indian Ocean, the models are inconsistent in their predictions for the signal to continue during the forecast period.

July 13, 2020

Subseasonal Weather Outlook (16 – 31 July 2020)

Issued 13 July 2020
Valid for weeks 3 and 4: 16 – 31 July 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the second fortnight of July 2020, wetter conditions are expected over much of the equatorial region of Southeast Asia. While the likelihood of these wetter conditions is similar for both weeks in the central and eastern equatorial region (Borneo, eastern Indonesia), there is some difference in the likelihood in the western equatorial region. In Week 3, wetter conditions are more likely for Sumatra and the southern Malay Peninsula, while in Week 4, wetter conditions are more likely for southern Thailand and southern Myanmar.

For northern Southeast Asia, drier conditions are expected over much of this region in Week 3, and becoming confined to western Myanmar in Week 4. During Week 3, the largest dry anomalies are expected over Myanmar, Lao PDR, and the northern Philippines.

Warmer conditions are expected over northern Southeast Asia, particularly in Week 3.

June 29, 2020

Subseasonal Weather Outlook (1 – 15 July 2020)

Issued 29 June 2020
Valid for weeks 1 and 2: 1 – 15 July 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first fortnight of July 2020, wetter conditions are expected over the equatorial regions of Southeast Asia, whereas drier conditions are expected over the northern and central parts of the Philippines.

In the first week of July, wetter conditions are expected over the southern parts of Mainland Southeast Asia.

Warmer conditions are expected over the northern and central parts of the Philippines, and the southern parts of the Maritime Continent for the first fortnight of July. For Mainland Southeast Asia, there is a higher likelihood of warmer conditions in the first week of July.

No discernible Madden-Julian Oscillation (MJO) signal is observed and there is no consistent signal in the models’ predictions for an MJO to develop in the forecast period.