MJO Fortnightly Update
Issued: 07 Oct 2026
While an active signal was present over the Western Hemisphere (Phases 8 and 1) in the first week of October based on the RMM index, its westward propagation was not characteristic of the Madden-Julian Oscillation (MJO). Most models predict no significant MJO activity by the start of the forecast period. During the forecast period (12 – 25 October), some models predict an MJO to emerge over the Indian Ocean (Phases 2 and 3) in Week 1 (12 – 18 October), while others suggest no significant MJO activity.
Period:
Location:
Figure 1: Below-normal and Above-normal rainfall frequencies for MJO phases based on GPCP (reference period: 2001-2020).
For each MJO phase, the below- and above-normal rainfall frequencies are computed as the ratio of days with values exceeding the lower upper tercile thresholds, respectively, to the total number of days in that phase.
N corresponds to the number of days for each MJO phase.
Figure 2: Correlation heatmap between RMM amplitude and 20–90 days bandpass-filtered daily rainfall anomalies based on GPCP data (Reference period: 2001–2020); Only correlation significant at the 95% level is shown.
MC = Maritime Continent; MSA = Mainland Southeast Asia.
The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.