Category Archives: Fortnightly Weather Outlook

CR58

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.

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 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.

June 15, 2020

Subseasonal Weather Outlook (16 – 30 June 2020)

Issued 15 June 2020
Valid for weeks 3 and 4: 16 – 30 June 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over most parts of the equatorial Maritime Continent in the second fortnight of June 2020.

Over northern Southeast Asia, drier conditions are expected in the second fortnight of June except for some coastal parts of Myanmar where wetter conditions are expected in Week 3.

Warmer conditions are expected over most parts of northern Southeast Asia, especially in Week 4. A higher likelihood of warmer conditions is also expected around the southeastern part of the Maritime Continent.

A Madden-Julian Oscillation (MJO) is currently present over the Indian Ocean. During the forecast period, most models predict the MJO to slow down as it enters the Maritime Continent. If the MJO continues to propagate, this would increase the likelihood of wetter conditions in the Maritime Continent.

May 28, 2020

Subseasonal Weather Outlook (1 – 15 June 2020)

Issued 28 May 2020
Valid for weeks 1 and 2: 1 – 15 June 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over most parts of the Maritime Continent in the first fortnight of June 2020. However, the wetter conditions may ease in the western Maritime Continent in Week 2.

Over Mainland Southeast Asia, particularly over parts of Myanmar and Lao PDR, drier conditions are expected in the first week of June. Drier conditions are also expected over northern and central parts of the Philippines over the first two weeks in June. The drier conditions are associated with weaker-than-normal Southwest Monsoon winds during the fortnight.

Warmer conditions are expected over most parts of Mainland Southeast Asia and northern and central Philippines, especially in Week 1. Over the Maritime Continent, a higher likelihood of warmer conditions is expected around the Java region.

A weak Madden-Julian Oscillation (MJO) is currently present over the Western Pacific. A number of models predict the MJO to continue propagating to the Western Hemisphere and Africa in the first week of June 2020, and possibly as far as the Indian Ocean in the week after.