Category Archives: Fortnightly Weather Outlook

CR58

February 19, 2021

Subseasonal Weather Outlook (22 February – 7 March 2021)

Issued 19 February 2021
First forecast week: 22 February – 28 February
Second forecast week: 1 March – 7 March

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are expected over the western Maritime Continent and southern Mainland Southeast Asia in Week 1 (22 – 28 February). There is a chance of these drier conditions persisting through Week 2 (1 – 7 March), although with lower confidence than Week 1. Wetter conditions are expected over central and northern Philippines in Week 1, but the location is highly dependent on tropical cyclone development.

Cooler temperatures than usual are expected around the Gulf of Thailand and southern parts of South China Sea, including southern Viet Nam, southern Cambodia, and the eastern coast of the Malay Peninsula in Week 1 (22 – 28 February). Warmer conditions than usual are expected over central Mainland Southeast Asia in Week 2 (1 – 7 March).

There are signs that an MJO signal is currently present over the Western Pacific (Phase 7), although the models are predicting this signal to rapidly weaken in Week 1. Some models are predicting another MJO to develop in Week 2 (Phase 7 or 8) and continue propagating eastward.

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.

February 5, 2021

Subseasonal Weather Outlook (8 – 21 February 2021)

Issued 5 February 2021
First forecast week: 8 February – 14 February
Second forecast week: 15 February – 21 February

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the Philippines and northern Borneo in the next fortnight (8 – 21 February). In Week 1 (8 – 14 February), there is an increased chance of wetter conditions over north-eastern Mainland Southeast Asia, as well as over southern Indonesia. In Week 2 (15 – 21 February), drier conditions are expected over the Malay Peninsula and western Borneo.

Warmer conditions than usual are expected over much of the Maritime Continent in Week 1 (8 – 14 February). Cooler temperatures than usual are expected over western Mainland Southeast Asia in Week 1, in particular Myanmar, northern Thailand and northern Lao PDR.

An MJO signal is currently present over the Western Pacific (Phase 6). The models are predicting a slow eastward propagation of the MJO, moving into Phase 7 in Week 1. In Week 2, models are either predicting the MJO to decay or continue slowly propagating eastward.

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.

January 22, 2021

Subseasonal Weather Outlook (25 January – 7 February 2021)

Issued 22 January 2021
First forecast week: 25 January – 31 January
Second forecast week: 1 February – 7 February

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For rainfall in Week 1 (25 – 31 January 2021), wetter conditions are predicted over much of the southern part of the ASEAN region. These wetter conditions are expected to become confined mainly to the region around Java in Week 2 (1 – 7 February 2021). There is also an increased chance of wetter conditions in Week 1 for southern parts of Mainland Southeast Asia as well as the northern Philippines.

For temperature, there is an increased chance of cooler conditions over the central part of the Maritime Continent, as well as southern Thailand, in Week 1 (25 – 31 January 2021). These cooler temperatures are expected to ease in Week 2 (1 – 7 February 2021).

The MJO signal that was present in the Maritime Continent (Phase 4) in the middle of January has weakened and is no longer discernable. Some models predict an MJO signal to emerge again in the Western Pacific (Phase 6 or 7) in Week 1.

January 8, 2021

Subseasonal Weather Outlook (11 – 24 January 2021)

Issued 8 January 2021
First forecast week: 11 January – 17 January
Second forecast week: 18 January – 24 January

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For rainfall in Week 1 (11 – 17 January 2021), an increased chance of wetter conditions is predicted over much of the Maritime Continent. Drier conditions are also predicted for regions around the Gulf of Thailand in Week 1. In Week 2 (18 – 24 January 2021), the wetter conditions are expected to ease, apart from over the Philippines and northern Borneo, with drier conditions expected to develop in parts of the western Maritime Continent.

An increased chance of cooler conditions is predicted over much of Mainland Southeast Asia and parts of the western Maritime Continent in Week 1 (11 – 17 January 2021) due to a surge of cool air blowing southward from the northern Asian landmass. In Week 2 (18 – 24 January 2021), the cooler conditions are expected to ease for much of this area, apart from central parts of Mainland Southeast Asia. Warmer conditions are expected to develop in the central and eastern equatorial region in Week 2.

An MJO signal is present over the Indian Ocean (Phase 3). Some models predict it to propagate eastward, entering the Maritime Continent by the end of Week 1.

December 24, 2020

Subseasonal Weather Outlook (28 December 2020 – 10 January 2021)

Issued 24 December 2020
First forecast week: 28 December – 3 January
Second forecast week: 4 January – 10 January

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the next fortnight (28 December 2020 – 10 January 2021), an increased chance of wetter conditions is predicted over parts of northern ASEAN region, in particular the Philippines, northern Borneo, southern Viet Nam, Cambodia, southern Thailand and Peninsular Malaysia. A lower increase in likelihood of wetter conditions is also predicted around the southeastern part of the Maritime Continent in the second week (4 – 10 January 2021).

An increased chance of cooler conditions is predicted over most of Mainland Southeast Asia in the next fortnight (28 December 2020 – 10 January 2021).

The Madden-Julian Oscillation (MJO) signal is becoming indiscernible over the Western Pacific (Phase 6). Some dynamical models predict the MJO to re-emerge over the Indian Ocean in early January 2021, propagating eastwards towards the Maritime Continent 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.

December 11, 2020

Subseasonal Weather Outlook (14 – 27 December 2020)

Issued 11 December 2020
First forecast week: 14 December – 20 December
Second forecast week: 21 December – 27 December

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the next fortnight (14 – 27 December), an increased chance of wetter conditions is predicted over the Philippines, parts of central and southern Viet Nam, southern Thailand and southern Myanmar. An increased chance of wetter conditions is also predicted around the southeastern part of the Maritime Continent in the first week (14 – 20 December). Drier conditions are predicted over parts of the equatorial region, in particular Borneo and central Sumatra for the next fortnight (14 – 27 December).

There is an increased chance of cooler conditions over southern parts of Indonesia in the first week (14 – 20 December), easing in the second week (21 – 27 December).

A weak Madden-Julian Oscillation (MJO) signal is present over the eastern Maritime Continent (Phase 5). Most models predict this MJO to continue propagating slowly eastwards over the Pacific, although weakening due in part to the La Niña conditions.

November 27, 2020

Subseasonal Weather Outlook (30 November – 13 December 2020)

Issued 27 November 2020
First forecast week: 30 November – 6 December
Second forecast week: 7 December – 13 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

An increased chance of wetter conditions is predicted over parts of northern ASEAN region in the next fortnight (30 November – 13 December), in particular central and southern Viet Nam, southern Thailand and northern Philippines. A higher likelihood of wetter conditions is also predicted around the southeastern part of the Maritime Continent. Drier conditions are predicted over parts of the equatorial region in the first week (30 November – 6 December).

Cooler temperatures than usual are predicted over parts of eastern Mainland Southeast Asia in the next fortnight (30 November – 13 December), with a higher confidence in the first week (30 November – 6 December). An increased chance of warmer conditions is predicted over parts of central Sumatra and Borneo in the first week (30 November – 6 December).

Current MJO signal is weak. The dynamical models are inconsistent regarding the MJO development in the forecast period.

November 13, 2020

Subseasonal Weather Outlook (16 – 29 November 2020)

Issued 13 November 2020
First forecast week: 16 November – 22 November
Second forecast week: 23 November – 29 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over parts of Sumatra, Malay Peninsula and western Borneo in the first week (16 – 22 November).

Warmer conditions are predicted over much of Mainland Southeast Asia during the next two weeks (16 – 29 November). Warmer conditions are also predicted over parts of Java, southern Borneo and southern Sulawesi in the first week (16 – 22 November), with conditions easing by the second week (23 – 29 November).

An MJO signal is present over the Western Hemisphere and Africa (Phase 8). Most models predict the MJO to continue propagating eastwards, weakening over the Indian Ocean (Phases 2 and 3).

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.

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.