Subseasonal Weather Outlook (27 December 2021 – 9 January 2022)

Issued: 24 December 2021
First forecast week: 27 December – 2 January
Second forecast week: 3 January – 9 January


Figure 1: Rainfall Outlook


Figure 2: Temperature Outlook


In Week 1 (27 December – 2 January), wetter conditions are expected over much of the Philippines, northern Borneo and northern Sulawesi. However, these wetter conditions are highly dependent on the tropical cyclone development. Also in Week 1, an increased chance of wetter conditions is predicted over parts of Viet Nam and the Malay Peninsula.

Cooler than usual temperature is expected over much of central and eastern Mainland Southeast Asia in Week 1 (27 December – 2 January) associated with a strengthening of the northeasterly winds, bringing cooler air from the northern Asian landmass. In Week 2 (3 – 9 January), these cooler conditions are expected to ease for much of this area.

Warmer than usual temperature is expected over southeastern parts of the Maritime Continent in Week 1 (27 December – 2 January).

Based on the RMM index, a Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phases 6 and 7) in December. Some models predict this signal to continue propagating slowly through the Western Pacific, while others predict the signal to decay 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.