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

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*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)

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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.

Regional maps of outgoing longwave radiation (OLR)

Click on the boxes to view a timeseries of cloudiness for that region.
Map of regional cloudiness Dateline Vanuatu Coral Sea Fiji Nauru & Tuvalu Solomon Islands New Guinea Northern Australia Micronesia Malaysia & Indonesia Guam & Marianas Philippines Indochina Southern India & Sri Lanka

Below: OLR totals over the dateline

Click to see full-size graph of 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.

Daily averaged OLR anomalies

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Westerly wind anomalies

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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.

Severe tropical cyclone Trevor over Cape York Peninsula

Severe tropical cyclone (TC) Trevor is expected to cross Queensland's east coast, south of the Lockhart River, later today (19 March). Trevor continues to intensify as it moves west-southwest towards Cape York Peninsula and will likely cross the coast as a category 3 or 4 system. Very destructive winds and abnormally high tides will accompany Trevor over the eastern Cape York Peninsula, and heavy rainfall—which may lead to flash flooding—is forecast for far north Queensland over the next few days.

Severe TC Trevor will weaken as it crosses Cape York Peninsula but is expected to re-intensify once over the Gulf of Carpentaria. Trevor reached category 1 intensity early Monday 18 March in the Coral Sea and rapidly intensified to a category 2 system.

For the latest tropical cyclone advice and track map, go to the Bureau's Current Tropical Cyclones.

Another tropical cyclone brewing off northwest Australia

A tropical low, north of Western Australia's Kimberley, is forecast to track west-southwest over the next few days and is likely to develop into a cyclone either Wednesday or Thursday. There is potential for the system to impact the Pilbara coast later in the week.

See the latest Tropical Cyclone Outlook for the Western Region.

Savannah heads west

TC Savannah formed on 14 March and moved south-southwest, passing to the west of Cocos Island. Savannah intensified into a category 4 system on 17 March, continues to track southwest through the Indian Ocean, and is unlikely to recurve to the east.

Chance for monsoon over the Northern Territory

The foci for cloud and rainfall over the Australian tropics currently are Severe TC Trevor to the northeast, and the developing low off the northwest. The monsoon trough is present in those areas but has broken down north of the Northern Territory (NT). Mostly clear skies over the Northern Territories central districts means the unusually warm and dry weather continues in those parts for the beginning of the week. Rabbit Flat (in the NT) broke the Australian record for consecutive days over 39 °C, which now stands at 109 days and counting. Further north, Darwin's 2018-19 wet season total is currently tracking as the second lowest rainfall-to-date on record. Darwin needs more than 137 mm by the end of April to avoid its driest wet season on record. However, as TC Trevor moves towards the Northern Territory it will bring heavy rainfall with it, and there is an increased chance the monsoon will develop over the Top End.

The tropics over the Maritime Continent are very active at the moment, with convective troughs, active Rossby Waves and a few tropical lows. As the Madden-Julian Oscillation (MJO) progressed eastward into the Maritime Continent region at the end of last week its signal weakened and became indiscernible amongst the other influences. International climate models agree that the MJO will remain indiscernible this coming week. As such, it is unlikely that the MJO will be a driving influence of tropical weather during this time.

Read more about the Bureau's current MJO monitoring.

El Niño ALERT

The El Niño–Southern Oscillation(ENSO) is currently neutral, however the Bureau's ENSO Outlook has been raised to El Niño ALERT. This means there is approximately a 70% chance of El Niño developing in the coming months, around triple the normal likelihood. El Niño ALERT is not a guarantee that El Niño will occur; it is an indication that some of the typical precursors of an event are in place.

See today's ENSO Wrap-Up for all the details.

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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.

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