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.
Tropical activity increases as monsoon develops in southern hemisphere
A tropical trough in the southern hemisphere Indian Ocean has strengthened in the last week, exhibiting characteristics typical of a monsoon trough, including a deep westerly wind flow, and increase in regional rainfall and cloudiness, particularly to the north of Australia and equatorial South-East Asia.
The monsoon trough in the southern hemisphere is located well north of the Australian mainland, featuring a tropical low south of Java. The low is expected to deepen and move westwards away from the Australian region in the next few days, but it is unlikely to reach tropical cyclone intensity.
A tropical trough in the northern hemisphere also intensified during the last week, contributing to the development of a significant tropical low which produced very heavy rainfall over parts of southern Thailand. This low is expected to strengthen to tropical cyclone intensity over the Bay of Bengal in the coming days. For further information on this tropical low see advice provided by the Indian Meteorological Department.
Madden–Julian Oscillation remains weak
The Madden–Julian Oscillation (MJO) has been weak or indiscernible in the last week and has not significantly impacted tropical rainfall patterns during that time.
Some climate models monitored by the Bureau of Meteorology predict a weak MJO signal may re-appear in the Indian Ocean in the coming week and move eastwards towards Maritime Continent longitudes early next week. If this scenario occurs, rainfall would typically be enhanced over the central Indian Ocean as well as parts of South-East Asia and the Maritime Continent. Rainfall over northern Australia is generally not impacted significantly by the effects of the MJO in these circumstances.
See the Bureau's current MJO Monitoring information.
Pacific Ocean expected to remain ENSO-neutral in the coming months
The likelihood of La Niña developing in the coming months is now considered low and the Bureau’s ENSO Outlook has shifted from La Niña WATCH to INACTIVE. When the ENSO Outlook is INACTIVE it means there are no signs of El Niño or La Niña developing in the coming months.
Across the Pacific Ocean, oceanic and atmospheric indicators of the El Niño–Southern Oscillation (ENSO) remain within neutral thresholds. There are some features across the Pacific Ocean basin that are suggestive of a weak La Niña-like pattern, such as the below-average convection and rainfall near the Date Line, but it is unlikely these patterns will persist.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and IOD information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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