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 and expected 850 hPa (approximately 1.5 km above sea level) wind anomalies for each of the 8 MJO phases. Green shades indicate higher than normal expected rainfall, while brown shades indicates lower than normal expected rainfall.

When the 'Wind' checkbox is selected, 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 Australian rainfall and winds 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

Climate driver influence on northern Australia

The 2021–22 La Niña has dissipated, with most indicators now depicting a neutral ENSO state (neither La Niña nor El Niño). However, some model outlooks suggest La Niña may re-form from spring 2022. As a result, the Bureau's ENSO Outlook status has moved to La Niña WATCH. La Niña WATCH means there is around a 50% chance of La Niña re-forming in 2022. This is approximately double the normal likelihood.

If La Niña redevelops in 2022, many parts of northern Australia would most likely see above-average rainfall in the early wet season period, potentially as early as September (the official northern wet season is October to April). La Niña typically also leads to above-average temperatures, particularly night-time temperatures, during the winter-spring period. Tropical cyclone (TC) activity across northern Australia is also influenced by La Niña, with the first TC of the TC season (November to April) often developing earlier than average. A La Niña wet-season period (October to April) typically sees average to above-average numbers of TCs. However, in recent years this has been moderated by the downwards trend in TC activity in the Australian region since 2000.

The Indian Ocean Dipole (IOD) index has been near or below the negative IOD threshold in the last 3 weeks. A negative IOD event is generally considered to have developed when the index has been close to or below the IOD threshold for around 8 weeks. Climate models indicate a negative IOD is likely to develop over winter.

Similar to the influence of La Niña, a negative IOD normally leads to above-average rainfall in the early wet-season period across much of northern Australia, although to a lesser extent than La Niña. When it comes to temperature, however, a negative IOD typically has a stronger influence than La Niña in producing warmer days and nights in the winter-spring period. The influence exerted by the negative IOD usually diminishes significantly by the end of spring or start of summer, and so while it has an influence on tropical cyclone activity around northern Australia, it is usually confined to increasing the likelihood of a first TC developing earlier than average.

Read more about climate drivers

Madden–Julian Oscillation in Indian Ocean

After stalling in the Africa region last week, a moderately strong pulse of the Madden-Julian Oscillation (MJO) tracked eastwards, into the tropical western Indian Ocean in recent days. While this pulse of the MJO is forecast to weaken slightly in the coming days, most climate models indicate it will remain as a coherent and discernible pulse of the MJO and track further east into the eastern Indian Ocean in the coming week.

At this time of the year, the influence on tropical rainfall patterns of an MJO pulse over the Indian Ocean is generally confined to north of the equator, although some parts of north-eastern Australia and the northern Maritime Continent are favoured to have above-average rainfall in this scenario.

Looking at the broadscale influence of the MJO in the coming fortnight, there is an increased likelihood that stronger-than-average trade winds (easterly winds) will prevail cross the tropical central and western Pacific Ocean. As a result, some La Niña indicators may briefly move closer to La Niña thresholds.

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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