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 moves over the Maritime Continent
The active convection of a Madden–Julian Oscillation (MJO) pulse moved across the Indian Ocean and into the Maritime Continent region during the last week. It has remained at moderate strength during the last fortnight, although most international climate models forecast the MJO to rapidly weaken in the coming days prior to reaching the western Pacific region.
When the MJO is over the Maritime Continent at this time of the year, cloudiness and rainfall is typically enhanced over Queensland and the Kimberley coastline in Western Australia. More significant rainfall associated with the passage of the MJO would typically be expected over locations further to Australia’s north.
See the Bureau's MJO Monitoring for current MJO information.
Widespread tropical activity over southern Asia
The passage of the MJO over the Indian Ocean coincided with onset of monsoon conditions over the Bay of Bengal. Also associated with the MJO was the formation of cyclonic storm Roanu, which initially developed north of Sri Lanka. The system then tracked northwards, remaining near to the east coast of India, before making landfall near the border of Bangladesh and Myanmar. Large rainfall totals were recorded as Roanu moved along India’s east coast and over southern Bangladesh’s low-lying Chittagong and Barisal regions, causing major flooding which led to fatalities and property damage.
In the northern Indian Ocean, widespread convection and rainfall currently extends from the monsoonal activity over the eastern side of the Bay of Bengal, across much of South East Asia and, most recently, into the northwestern Pacific Ocean. With the MJO over Maritime Continent longitudes the risk of tropical cyclone formation over the northwest Pacific Ocean is elevated this week. There is also a heightened tropical cyclone risk over the northern Bay of Bengal associated with the presence of an active monsoon trough.
The long-term means for tropical cyclone formation during May are 1.3 tropical storms (0.8 typhoons) for the western North Pacific Ocean, 1.0 for the South Pacific and southern Indian Oceans combined and 0.7 occurrences in the northern Indian Ocean, including the Bay of Bengal.
El Niño ends as tropical Pacific Ocean returns to neutral
Sea surface temperatures in the Pacific Ocean have returned to a neutral El Niño-Southern Oscillation (ENSO) state, with little chance of returning to El Niño levels. Model outlooks and current observations indicate there is at least a 50% likelihood of La Niña developing in the second half of 2016 – about double the normal chance. La Niña has little implication for tropical Australia during the dry season. However, La Niña is often, but not always, associated with above-average wet season rainfall over tropical northern Australia. La Niña is also associated with a more active tropical cyclone season with an earlier start to the cyclone season for Australia. The other possible outcome, ENSO-neutral (neither El Niño nor La Niña), does not necessarily mean average rainfall, as the influence from other climate drivers, such as the Indian Ocean Dipole, may be significant.
Very warm sea surface temperatures continue across waters off the northern Australia coastline. Warmth from this region is expected to contribute to above-average temperatures across northern Australia in the coming months.
See the Bureau of Meteorology's ENSO Wrap-Up for official El Niño information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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