Category Archives: Fortnightly Weather Outlook

CR58

May 28, 2021

Subseasonal Weather Outlook (31 May – 13 June 2021)

Issued 28 May 2021
First forecast week: 31 May – 6 June
Second forecast week: 7 June – 13 June

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For Mainland Southeast Asia, an increased chance of drier conditions is predicted over much of the region in Week 1 (31 May – 6 June). In Week 2 (7 – 13 June), wetter conditions may develop over the western coastal region.

Elsewhere in the next fortnight (31 May – 13 June), an increased chance of drier conditions is predicted over much of the southern ASEAN region, particularly over the central equatorial region. Wetter conditions than usual are expected over central and southern Philippines in the next fortnight.

Warmer temperatures than usual are expected over much of the ASEAN region in Week 1 (31 May – 6 June), in particular over Mainland Southeast Asia, northern Philippines and parts of the southern Maritime Continent.

Towards the end of May, an MJO signal was present over the Western Pacific (Phase 6). However, this MJO signal is no longer discernible based on the RMM Index and the models are uncertain as to how the MJO will evolve over the forecast period.

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.

May 14, 2021

Subseasonal Weather Outlook (17 – 30 May 2021)

Issued 14 May 2021
First forecast week: 17 May – 23 May
Second forecast week: 24 May – 30 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

An increased chance of wetter conditions is expected over parts of the eastern Maritime Continent in Week 1 (17 – 23 May). Models are also predicting wetter conditions over southern Viet Nam and Cambodia, although with a lower confidence compared to the eastern Maritime Continent.

Drier conditions than usual are expected over much of northwestern Mainland Southeast Asia in Week 1 (17 – 23 May).

Warmer temperatures than usual are expected over much of northwestern Mainland Southeast Asia in Week 1 (17 – 23 May). These warmer temperatures are expected to ease and become confined mainly to northern parts of Myanmar and Lao PDR in Week 2 (24 – 30 May).

A weak Madden-Julian Oscillation (MJO) signal was present over the Indian Ocean (Phases 2 and 3). While the MJO signal is expected to be less coherent at the start of the forecast period, most models forecast the MJO to propagate eastwards and move into the Maritime Continent (Phase 4) by middle of Week 1. By end of May, some models predict the MJO to reach the Western Pacific (Phases 6 and 7).

April 30, 2021

Subseasonal Weather Outlook (3 – 16 May 2021)

Issued 30 April 2021
First forecast week: 3 May – 9 May
Second forecast week: 10 May – 16 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over parts of the western and central Maritime Continent in Week 1 (3 – 9 May) and may extend northward to coastal regions of southern Viet Nam. These wetter conditions are expected to ease in Week 2 (10 – 16 May) and be confined mainly to northern Sumatra and Peninsular Malaysia.

Drier conditions than usual are expected over much of the southern parts of the Maritime Continent in the next fortnight (3 – 16 May).

Cooler temperatures than usual are expected over parts of the western and central Maritime Continent in the next fortnight (3 – 16 May).

A strong Madden-Julian Oscillation (MJO) signal was present over the Western Hemisphere and Africa (Phase 8) at the end of April. Most models forecast the MJO to weaken in May as it propagates eastwards, decaying over the Indian Ocean towards the end of Week 1.

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.

April 16, 2021

Subseasonal Weather Outlook (19 April – 2 May 2021)

Issued 16 April 2021
First forecast week: 19 April – 25 April
Second forecast week: 26 April – 2 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over northern and central Philippines in Week 1 (19 – 25 April) associated with tropical cyclone activity. There is also a chance of wetter conditions over southern Myanmar, southern Thailand, southern Cambodia, and central and southern Viet Nam in Week 1.

Drier conditions than usual are expected over much of the southern ASEAN region in Week 1 (19 – 25 April). The drier conditions are expected to ease in Week 2 (26 April – 2 May).

Cooler temperatures than usual are expected over central and southeastern Mainland Southeast Asia, as well as northern and central Philippines, in the next fortnight (19 April – 2 May).

A strong Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phase 7) in the middle of April. Most models predict this signal to continue propagating eastwards during the next fortnight, entering the Western Hemisphere and Africa (Phase 8) by Week 2.

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.

April 1, 2021

Subseasonal Weather Outlook (5 – 18 April 2021)

Issued 1 April 2021
First forecast week: 5 April – 11 April
Second forecast week: 12 April – 18 April

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over much of the northern ASEAN region as well as northern Borneo, northern Sulawesi, and Maluku Islands in the next fortnight (5 – 18 April). In particular, for Week 1 (5 – 11 April) the highest probability of wetter conditions is over northern Lao PDR and much of Thailand. For Week 2 (12 – 18 April), the highest probability for wetter conditions is over southern Thailand, Cambodia, southern Viet Nam, and the Philippines.

Conversely, slightly drier conditions than usual are expected over much of the southern ASEAN region in Week 1 (5 – 11 April). There is a chance that these drier conditions may continue into Week 2 (12 – 18 April), although the confidence is low.

Cooler temperatures than usual are expected over much of Mainland Southeast Asia in the next fortnight (5 – 18 April), in line with the wetter conditions predicted. Warmer conditions than usual are expected over most of the equatorial region in Week 1 (5 – 11 April) and are expected to return to near-normal in Week 2 (12 – 18 April).

A moderate Madden-Julian Oscillation (MJO) signal was present over the Maritime Continent at the start of April. Models predict this MJO signal to continue propagating eastwards reaching the Western Pacific (Phase 6) at the start of Week 1, before weakening in Phase 7.

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.

March 19, 2021

Subseasonal Weather Outlook (22 March – 4 April 2021)

Issued 19 March 2021
First forecast week: 22 March – 28 March
Second forecast week: 29 March – 4 April

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the eastern Maritime Continent in the next fortnight (22 March – 4 April). In Week 1 (22 – 28 March), wetter conditions are also expected over northern and central parts of Sumatra, the Malay Peninsula and western Borneo. Also in Week 1, drier conditions are expected over eastern parts of Mainland Southeast Asia.

Warmer conditions than usual are expected over most of Mainland Southeast Asia, in particular for Myanmar in Week 1 (22 – 28 March) and spreading elsewhere in Week 2 (29 March – 4 April). Cooler temperatures than usual are expected over northern parts of Sumatra, the Malay Peninsula and western Borneo in Week 1.

A moderate Madden-Julian Oscillation (MJO) signal was present over the Western Hemisphere and Africa (Phase 1). Models predict this MJO to continue propagating eastwards over the Indian Ocean (phases 2 and 3), although weakening slightly as it approaches the Maritime Continent (phases 4 and 5) at the end of March.

March 6, 2021

Subseasonal Weather Outlook (8 – 21 March 2021)

Issued 6 March 2021
First forecast week: 8 March – 14 March
Second forecast week: 15 March – 21 March

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the Philippines in Week 1 (8 – 14 March), easing in Week 2 (15 – 21 March). In Week 2, there is also an increased chance of wetter conditions over the Malay Peninsula, Sumatra and coastal parts of western Borneo.

Warmer conditions than usual are expected over northwestern Mainland Southeast Asia in the next fortnight (8 – 21 March).

Current MJO signal is weak. Some models predict an MJO to re-emerge over the Western Hemisphere and Africa (Phases 8 and 1) during the forecast period and propagate eastwards towards the Indian Ocean.

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.

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.