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.
Methodology: Until the end of 2013 we use the exact method of Wheeler and Hendon (2004, https://doi.org/10.1175/1520-0493(2004)132%3C1917:AARMMI%3E2.0.CO;2) and from 2014 we use the modified method of Gottschalck et al. (2010, https://doi.org/10.1175/2010BAMS2816.1).

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.
Read more: The Combined Influence of the Madden–Julian Oscillation and El Niño–Southern Oscillation on Australian Rainfall.

Maps of total and anomaly outgoing longwave radiation (OLR)

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.

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)

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.

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

Daily averaged OLR anomalies

Westerly wind anomalies

Westerly wind anomalies

July to September long-range forecast

The Bureau's seasonal forecast (issued on 27 June) shows that for July to September – the latter part of the northern dry season – most of the southern half of the NT is likely to have above average rainfall while below average rainfall is likely in the far north, although rainfall is generally low at this time of year. Elsewhere, rainfall is likely to be within the typical seasonal range. There is an increased chance of unusually warm maximum and minimum temperatures across northern Australia. Unusually warm temperatures are those in the warmest 20% of observations in the given forecast period (July–September) between 1981 and 2018.

In northern Australia, June to November is generally considered bushfire risk season, with peak fire danger peaking in spring for much of the Australian tropics. However, for the far north, including the north-west coast of the NT and the northern Kimberley of WA, the fire danger peak can occur in mid to late winter.

The winter 2024 outlook issued by AFAC, the National Council for fire and emergency services,  indicates no increased bush fire risk for northern Australia. 

To read more about the fire seasons, visit the Bureau's  Fire Weather Knowledge Centre.

Late-season high maximum and minimum temperatures

A number of late season high maximum and minimum temperature records have been set across northern Australia in the last fortnight . Sites across the northern NT, north-western WA and much of Queensland had highest on record maximum and minimum temperatures in June, with some records exceeding their previous record by more than 2 °C.

Madden-Julian Oscillation

The Madden–Julian Oscillation (MJO) has been weak since the start of June. A weak pulse of the MJO has entered the eastern Indian Ocean, and is likely to weaken further and become indiscernible in early July. At this time of year, the MJO has little impact on Australian rainfall.

Later than usual rainfall onset likely for parts of northern Australia

The first issue of the northern rainfall onset forecast for the 2024–25 season indicates a later than usual onset for western and northern parts of Australia, and an earlier than usual onset for eastern parts.

The northern rainfall onset date occurs when the rainfall total reaches 50 mm since the 1st of September. It is considered to be approximately the amount of rainfall required to stimulate plant growth. The forecast will be updated monthly until the end of August.

The northern rainfall onset is greatly affected by the phase of the El Niño-Southern Oscillation (ENSO). ENSO is currently neutral. The Bureau's ENSO Outlook is at La Niña Watch due to early signs that a La Niña may form in the Pacific Ocean later in the year. A La Niña (or near–La Niña) pattern typically drives an earlier than normal onset of northern rainfall.

Product code: IDCKGEW000

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

Product Code: IDCKGEM000

Climate