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.

ENSO neutral, but 50% chance of El Niño developing

The El Niño–Southern Oscillation (ENSO) remains neutral—neither El Niño nor La Niña. However, warming in the tropical Pacific Ocean and recent model outlooks suggest an increased likelihood of El Niño developing during the Australian spring. As a result, the Bureau's ENSO Outlook is at El Niño WATCH, meaning there is roughly a 50% chance of El Niño developing later in the year (double the climatological average). Much of Queensland and the Northern Territory typically experiences drier than average conditions in the lead up to, and early part of, the northern wet season (October to April) during El Niño.

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

Madden–Julian Oscillation likely to move over western Pacific Ocean and weaken

Cloudiness and rainfall has been enhanced over parts of South-East Asia and the north western tropical Pacific Ocean this past week. This is likely associated with a moderate to strong eastward moving pulse of the Madden–Julian Oscillation (MJO) which has been detected over these regions during this period.

Most international climate models indicate the MJO will continue its eastward progression into the Western Pacific and weaken. Before weakening, it could increase the likelihood of cloudiness and rainfall over the northwestern tropical Pacific Ocean and increase the risk of tropical cyclone development in this region.

The MJO generally has little effect on Australian climate at this time of year. See the Bureau's current MJO monitoring for more information.

An increase in cloudiness over the Indian subcontinent this past week indicated that some regions experienced an active monsoon this past week. Check the India Meteorological Department website for information about the Indian Monsoon.

Tropical cyclone activity continues over western north Pacific region

The Madden–Julian Oscillation also contributed to ongoing tropical cyclone activity across the western north Pacific Ocean this past week. The very intense typhoon Maria formed in the northwest Pacific on the 8 July and peaked at a maximum intensity equivalent to a category 5 tropical cyclone in Australia. Maria later weakened as it moved north westward, and made landfall on the eastern Chinese coast on 11 July at a strength comparable to an Australia category 3 system. Maria weakened rapidly to below tropical cyclone strength after crossing the Chinese coast, but generated heavy rainfall across Japan's southern Ryukyu Islands, northern Taiwan and parts of eastern China during its passage. Maria was an especially notable tropical typhoon due to its rapid intensification. Analysis by the United States Joint Typhoon Warning Centre indicated Maria strengthened from a category 1 to a category 5 hurricane (or equivalent tropical cyclone intensity at http://www.bom.gov.au/cyclone/about/intensity.shtml) in the space of just 24 hours on 5 July—one of the fastest developing systems ever recorded.

Tropical cyclone Son-Tinh, which reached tropical cyclone strength in the northwest Pacific Ocean on 17 July, is expected to impact parts of the Philippines, the Chinese island of Hainan, and Vietnam in the coming days. See the Japanese Meteorological Agency 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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