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.
Read more: About the MJO
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.
Download data: RMM Data Postscript: RMM 40 days | RMM 90 days
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).
Print (PDF): JFM | FMA | MAM | AMJ | MJJ | JJA | JAS | ASO | SON | OND | NDJ | DJF
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).
Print (PDF): JFM | FMA | MAM | AMJ | MJJ | JJA | JAS | ASO | SON | OND | NDJ | DJF
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.
Postscript: 1 day | 3 days | 7 days | 3 months | 6 months | 1 year
Regional maps of outgoing longwave radiation (OLR)
Below: OLR totals over the dateline
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.
Imogen gives way to monsoon break across northern Australia
Ex-tropical cyclone (TC) Imogen and associated low-pressure troughs generated heavy rain across the tropical coast of eastern Queensland during the past week. The coastal strip between Cooktown and Mackay, along with the region near the base of Cape York Peninsula where Imogen traversed, saw widespread 7-day (to 11 January) rainfall totals in excess of 200 mm. The highest weekly total to 11 January was at Gairloch, near Ingham, with 550.2 mm. Significant disruption due to riverine flooding was also experienced across parts of northern Queensland.
Ex TC- Imogen has moved off the Queensland coast and weakened, and is not expected to significantly affect the tropical coast of Queensland in the coming days. Along with the rest of northern Australia, tropical Queensland is likely to be dominated by easterly trade winds in the coming week. These will contribute to further shower activity for eastern Queensland, but maintain relatively settled conditions across other parts of the Australian tropics. When trade winds dominate northern Australia at this time of the year, the monsoon is classified as inactive—this phase of the Australian monsoon is also known as a monsoon break.
While Australia is experiencing monsoon break conditions, a monsoon trough lies over the Indian Ocean, extending from south of Java, Indonesia, towards the central Indian Ocean. A tropical low within the monsoon trough, well west of Australia, has the potential to intensify, but is forecast to move further away from the Australian coast in the coming days.
Monsoon conditions may redevelop across Australia in the next fortnight
Climate and weather models indicate that a monsoon trough may develop across Australian longitudes in about a week, as broadscale atmospheric conditions become favourable for increased tropical weather. If a monsoon trough moves over northern Australia, the monsoon phase would change from break to active, and widepsread rainfall and tropical cyclone development would become more likely.
The change from a break to an active monsoon is typically induced by changes in the tropical wind patterns around Australia's longitudes or the influence of an approaching tropical atmospheric wave, such as the Madden–Julian Oscillation (MJO).
Madden–Julian Oscillation strengthens over the Indian Ocean
A pulse of the Madden–Julian Oscillation (MJO) has strengthened over the Indian Ocean in the past week. While the climate models surveyed by the Bureau indicate eastwards movement, there is disagreement amongst models as to the forecast strength of the MJO pulse in the coming fortnight.
Combined with another type of tropical atmospheric wave, an equatorial Rossby wave, the MJO is likely to contribute to an increase in tropical convection and rainfall and an above-average tropical cyclone risk around northern Australia in about a week. This is reflected in the latest climate outlook released by the Bureau, which shows a strong signal for above-median rainfall in the period 16–29 January.
Read more about the Madden–Julian Oscillation
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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