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.