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.

Fifth tropical cyclone for 2017-18

Tropical cyclone Joyce was the fifth in the Australian region for the 2017-18 tropical cyclone season, and the second to make landfall. Cyclone season continues until 30 April 2018. All five tropical cyclones have been confined to the Western Region. The first two cyclones of the season (Cempaka and Dahlia) moved southwest from south of Indonesia towards northwest Australia, while the three subsequent systems (Hilda, Irving and Joyce) formed, and remained within the Western Region. The start of the current season has been much more active than that of 2016-17, when only one tropical cyclone (Yvette) formed prior to February 2017.

Joyce was the second tropical cyclone to affect Western Australia's Kimberley region within three weeks. Joyce began as a tropical low which developed off the far northern Kimberley coast on 7 January, and then intensified to tropical cyclone strength on the morning of 11 January.  Tropical cyclone Joyce moved over land during the afternoon of 12 January before it strengthened beyond category 1. As a result, wind damage was limited; heavy rainfall and flooding were the main impacts associated with the system. Some coastal locations in the southwest Kimberley observed rainfall totals in excess of 250 mm.

Weak monsoon trough to Australia's northwest

A monsoon trough has been over Australia's northwest (predominantly offshore) since the beginning of January and remains active, but relatively weak. Forecast models suggest the trough will remain over waters to Australia's northwest but is not expected to strengthen significantly in the coming week.

International climate models predict the Madden–Julian Oscillation (MJO), currently over the Indian Ocean, will move into the western Maritime Continent in the coming week. The MJO in this region would typically assist in invigorating a pre-existing monsoon trough over northwest Australia, however, the broadscale weather pattern in the region is currently not favourable for this to occur. This is primarily due to an out-of-season tropical low which is currently located off the north coast of Borneo. This low is drawing in the energy associated with a surge of winds from the South China Sea which might otherwise cross the equator and energise the monsoon trough in the Australian region. The presence of tropical lows in the northern Indian Ocean during the austral summer has been a recurring theme during the current Australian wet season, and has played a significant role in the lack of monsoonal activity across northern Australia to date.

See the Bureau's current MJO monitoring for more information.

Weak La Niña in the tropical Pacific Ocean

Weak La Niña conditions persist in the tropical Pacific. Climate models suggest this La Niña will decay in the southern autumn of 2018. La Niña typically brings above average rainfall to eastern Australia parts of northern Australia during summer. However, weak events typically mean a weaker influence on Australian rainfall.

See the Bureau's current ENSO Wrap-Up for more information.

 

 

 

 

 

 

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

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