Madden Julian Oscillation Erupts

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Madden Julian oscillation erupts…a warming influence on U.S.

Fig. 1: A moderate-strength convection phase of the Madden Julian oscillation emerges throughout Indonesia.

Discussion: In recent days the Madden Julian oscillation has emerged across Indonesia (Fig. 1). Due to the increased attendant heavy convection, the atmosphere has become increasingly supportive of tropical cyclone activity. In the West Pacific tropics Typhoon Nyatoh has developed. This system reaches category-2 tropical cyclone strength while turning north and northeast over the next couple days. MJO also spawned a tropical depression well northwest of Australia.

The 2-week forecast based on the ECMWF outlook reveals an eastward shift of the MJO firmly into the tropical West Pacific and approaching the Dateline (Fig. 2). The intensity is moderate and considered influential on the mid-latitude weather pattern.

The strongest influence of the strengthening MJO in phase_6 is across Indonesia and northeastern Australia (Fig. 3). Both zones are wetter than normal. There’s a tendency for west-southwest wind across Indonesia during MJO phase_6 which could initiate the monsoon low pressure trough. Typically, the monsoonal trough develops in late December.

In the U.S., the MJO phase_6 typically increases a warming influence of the Pacific jet stream. MJO phase_6 climatology supports widespread anomalous warmth for the U.S. ahead (Fig. 4).

Fig. 2: The ECMWF 2-week MJO forecast indicates moderate-strength shifting across the West Pacific tropics (phase_6).

Fig. 3: MJO phase_6 climatology in the tropics favors heavy convection/rains across Indonesia to northeast Australia while the Indian Ocean is much drier.

Fig. 4: MJO phase_6 climatology for the U.S. favors widespread anomalous warmth.