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 east 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

La Niña is underway

Key atmospheric and oceanic indicators of the El Niño–Southern Oscillation (ENSO) show an established La Niña in the equatorial Pacific Ocean. As a result, the Bureau's ENSO Outlook has been raised to LA NIÑA status. A majority of surveyed climate models indicate this La Niña event may peak during spring or early summer and return to neutral conditions in early 2023.

A La Niña event typically increases the chance of above-average spring and summer rainfall across much of northern Australia. La Niña years are also associated with an average to above-average number of tropical cyclones in a season—the average number across the Australian region for all years since 2000 is about 9 per season (November—April) as well as an increased likelihood of tropical cyclone activity occurring during November. The monsoon onset date at Darwin occurs about a week or so earlier than usual during a La Niña event, typically around mid-December.

Wet outlook a combination of climate drivers

A relatively strong negative Indian Ocean Dipole (IOD) event continues. Climate models indicate the negative IOD is likely to persist into at least late spring and dissipate in early summer—typical of most IOD events. A negative IOD is associated with above-median spring rainfall for the Northern Territory, Queensland and much of southern Australia. It also typically increases the chances of warmer days and nights for much of tropical northern Australia.

During negative IOD years, the chance of observing a tropical cyclone across the Australian region in November increases, compared to positive or neutral IOD years.

Warmer-than-average sea surface temperatures around much of Australia also favour above-average rainfall across much of Australia in the coming months. Climate outlooks indicate warmer waters around northern and western Australia are likely to persist into early summer.

The collective influence of the above climate drivers is displayed in the Bureau's latest climate outlooks which show increased likelihood of above-median rainfall across most of the Northern Territory and Queensland during the first 3 months of the coming wet season (i.e. October to December).

Read more about climate drivers in the Climate Driver Update.

Madden–Julian Oscillation remains weak

The Madden-Julian Oscillation (MJO) has been weak or indiscernible since the start of September. All surveyed models indicate the MJO will remain weak until at least the end of this month. As a result, rainfall patterns across the Australian and Maritime Continent regions are not expected to be influenced by the MJO in the coming fortnight.

Read more about the Madden–Julian Oscillation (MJO).

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

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