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 phase diagram
*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.
The MJO phase diagram illustrates the progression of the MJO through different phases, which generally coincide with locations along the equator around the globe. 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 the index is within the centre circle the MJO is considered weak, meaning it is difficult to discern using the RMM methods. 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. For convenience, we define 8 different MJO phases in this diagram.
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 and blue shading indicates higher than normal rainfall would be expected, while red and orange shading indicates lower than normal rainfall would be expected. 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 (which can be selected at the top).
Average outgoing longwave radiation (OLR)
Outgoing longwave radiation (OLR) is often used as a way to identify tall, thick, convective rain clouds. These maps show the difference from expected cloudiness based on the position of the MJO. The violet and blue shading indicates higher than normal, active or enhanced tropical weather, while orange shading indicates lower than normal cloud or suppressed conditions. 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 tropical weather patterns changes with the season (which can be selected above the maps).
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.
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.
Postscript: Coral Sea Dateline Fiji Guam & Marianas Indochina Malyasia & Indonesia Micronesia Nauru & Tuvalu New Guinea Northern Australia Philippines Solomon Island Southern India & Sri Lanka Vanuatu
Daily averaged OLR anomalies
Westerly wind anomalies
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.
Madden–Julian Oscillation has weakened
In the Indian Ocean, cloudiness and rainfall was enhanced along the equator this past week, as a strong Madden–Julian Oscillation (MJO) moved eastwards over the region before weakening prior to reaching Maritime Continent longitudes.
Most climate models monitored by the Bureau of Meteorology predict the MJO will weaken further and become indiscernible in the next fortnight. While some models suggest the MJO may briefly and marginally strengthen in about a week’s time, no models indicate the signal will strengthen significantly in the coming fortnight and none predict the MJO will enhance cloudiness and rainfall across the Maritime Continent or northern Australia during that period.
Tropical wave activity is not expected to significantly impact rainfall patterns over the Maritime Continent in the coming week. The dominant driver of tropical weather in the Maritime Continent region is expected to be associated with a burst of westerly winds, which most models forecast for the coming week. This westerly wind burst is a typical feature at this time of the year (see wind analysis chart here) and has the potential to significantly enhance rainfall in parts of the Maritime Continent and South-East Asia.
See the Bureau's current MJO Monitoring information.
ENSO-neutral state continues in the Pacific Ocean
The El Niño–Southern Oscillation (ENSO) remains neutral but continues to show some La Niña-like attributes. In the central Pacific Ocean, sea surface temperatures are slightly cooler than the long-term average, however they remain within neutral bounds and are forecast by most international climate models to remain so for the next few months. The atmosphere above the tropical Pacific Ocean, as indicated by the Southern Oscillation Index and the trade wind regime, also reflects an ENSO-neutral state.
There are some features across the Pacific basin that are suggestive of a La Niña-like pattern, such as warm waters around northern Australia’s coastline and the below-average convection and rainfall near the Date Line, but without coupling between the ocean and the atmosphere, a well-developed La Niña will not become established in the Pacific.
The Indian Ocean Dipole has returned to neutral levels after being in a negative phase since May.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and IOD information.
Product code: IDCKGEW000
ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
Product Code: IDCKGEWWOO