Madden-Julian Oscillation (MJO)

The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days.


MJO location and strength

These graphs show the strength and progression of the MJO through 8 different areas along the equator around the globe.
Area 3 is north west of Australia, 4 and 5 are to the north (the Maritime Continent), and 6 is to the north east.

RMM1 and RMM2 are mathematical methods that combine cloud amount and winds at upper and lower levels of the atmosphere to provide a measure of the strength and location of the MJO. When this index is within the centre circle the MJO is considered weak. Outside of this circle the index is stronger and will usually move in an anti-clockwise direction as the MJO moves from west to east.

MJO phase diagram
MJO phase diagram

*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.

Average weekly rainfall probabilities

These maps show average weekly rainfall probabilities for each of the 8 MJO phases. Green shades indicate higher than normal expected rainfall, while brown shades indicates lower than normal expected rainfall.

Select the 'Wind' checkbox to also show the expected 850 hPa (approximately 1.5 km above sea level) wind anomalies. The direction and length of the arrows indicate the direction and strength of the wind anomaly. The darker the arrow, the more reliable the information is.

The relationship of the MJO with global weather patterns changes with the season

Global maps of outgoing longwave radiation (OLR)

Global maps of outgoing longwave radiation (OLR) highlight regions experiencing more or less cloudiness. The top panel is the total OLR in Watts per square metre (W/m²) and the bottom panel is the anomaly (current minus the 1979-1998 climate average), in W/m². In the bottom panel, negative values (blue shading) represent above normal cloudiness while positive values (brown shading) represent below normal cloudiness.

Maps of total and anomaly outgoing longwave radiation (OLR)

Regional maps of outgoing longwave radiation (OLR)

The graphs linked to this map show the OLRs for the different regions within the Darwin RSMC area. The horizontal dashed line represents what is normal for that time of year (based on the 1979 to 1998 period). The coloured curve is the 3-day moving average OLR in W/m². Below normal OLR indicates cloudier than normal conditions in this particular area, and is shown in blue shading. Above normal OLR indicates less cloudy conditions and is shown in yellow shading.

Tap boxes to view a timeseries graph of cloudiness for that region
image/svg+xml Southern India and Sri Lanka Southern India and Sri Lanka Indochina Indochina Philippines Philippines Malaysia and Indonesia Malaysia and Indonesia Guam and Marianas Guam and Marianas Micronesia Micronesia Northern Australia Northern Australia Coral Sea Coral Sea Vanuatu Vanuatu Fiji Fiji New Guinea New Guinea Solomon Islands Solomon Islands Nauru and Tuvalu Dateline Dateline

OLR totals over the dateline

OLR totals over the dateline (area at far right in region map above)

Time longitude plots

Time longitude plots of daily averaged OLR anomalies (left) and 850 hPa (approximately 1.5 km above sea level) westerly wind anomalies (right) are useful for indicating the movement of the MJO.

How to read the Time longitude plots

The vertical axis represents time with the most distant past on the top and becoming more recent as you move down the chart. The Horizontal axis represents longitude.

Eastward movement of a strong MJO event would be seen as a diagonal line of violet (downward from left to right) in the OLR diagram, and a corresponding diagonal line of purple in the wind diagram. These diagonal lines would most likely fall between 60°E and 150°E and they would be repeated nearly every 1 to 2 months.

Daily averaged OLR anomalies

Westerly wind anomalies

Monsoon Burst to Return to Northern Australia

The monsoon is set to return to northern Australia in the coming week and its return will likely bring increased rainfall across the region. This will coincide with the forecast eastward movement of the Madden–Julian Oscillation (MJO) into the Maritime Continent (MC) in early February.

Northern Australia has been in a monsoon break period over the last week but there were periods of storms and squalls that were experienced across the region. Further rainfall was experienced in the Kimberley region of Western Australia as a weak tropical low (10U) influenced the weather across the region, associated with the passage of an equatorial Rossby (ER) wave. The rainfall recorded was less than that received during ex-tropical cyclone Ellie at the end of December and early January, thus did not cause further flooding in the Fitzroy River catchment.

As the monsoon returns across the region this week, tropical lows may develop within it, most likely in the Indian Ocean south of the Indonesian archipelago and near the western Maritime Continent. More information on the current tropical cyclone forecast can be found in the Tropical Cyclone Outlooks

February and March are the peak period for tropical cyclone activity across northern Australia. In addition, the La Niña in the Pacific continues, so broad environmental conditions remain favourable for tropical cyclone formation.

 

Madden–Julian Oscillation Will Weaken and Move to the Maritime Continent

The Madden–Julian Oscillation (MJO) is forecast to weaken from its moderate to strong intensity in the eastern Indian Ocean and is forecast to move over the Maritime Continent in early February. Although the MJO is forecast to weaken as it tracks across the Maritime Continent region and into the Western Pacific region, it is likely to have an influence on tropical weather through to mid-February.

Read more about the Madden–Julian Oscillation

Product code: IDCKGEW000

ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.

Product Code: IDCKGEM000

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