Category Archives: Fortnightly Weather Outlook

CR58

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.

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 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.

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.