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.
Monsoon break in the north as rainfall moves inland
With the recent dissipation of the monsoon trough over northern Australia, much of the region has experienced an inactive period in the monsoon this week, with many locations receiving only minimal rainfall from isolated showers and storms. Instead, an active trough has persisted further south for much of the week, focusing rainfall over parts of northern Western Australia, central Northern Territory, and Far North Queensland. Rainfall over these regions has been well above average, including isolated daily totals in excess of 100 mm. In particular, Tennant Creek (Northern Territory) experienced a 1-in-50 year rainfall event when 70 mm fell in just over an hour, resulting in flash flooding. A low which developed over northwest Queensland during the weekend is expected to continue to move west over the coming days, bringing with it the possibility of further heavy falls and flooding to already saturated parts of the central NT and northern WA. Reduced rainfall conditions in the far north are expected to persist for the next few days, before a possible increase in more monsoonal-like activity early next week.
Madden-Julian Oscillation currently weak, may strengthen
Heavy rainfall observed over parts of inland northern Australia this week is not related to the Madden-Julian Oscillation (MJO), which has remained weak or indiscernible over recent weeks. There is a strong consensus between climate models that the MJO will strengthen over the western hemisphere in the next few days. When the MJO is in the western hemisphere at this time of year, the focus of tropical convection is shifted to Africa and the Indian Ocean, while the northern Australian and Maritime Continent regions typically experience decreased cloudiness and rainfall.
Australia’s tropical cyclone season has been relatively quiet so far, with only one named system in late December (Tropical Cyclone Yvette). Some models predict the MJO will progress eastward reaching Australian longitudes by the end of the month. As the MJO moves eastward the risk of tropical cyclone development in the Australian region will increase. For more information on tropical cyclones affecting the Australian region, please check the Bureau’s tropical cyclone webpage.
For more information see the Bureau's current MJO monitoring information.
ENSO-neutral conditions to continue
The El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean remains neutral, and most climate models predict it will remain so throughout the Australian summer and autumn. Most ocean temperatures and atmospheric indicators of ENSO remain within the neutral range.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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