Madden-Julian Oscillation (MJO)


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.

La Niña likely to remain until at least the end of summer 2020–21

The Bureau’s ENSO Outlook remains at LA NIÑA. Sea surface temperatures in the central and tropical Pacific Ocean continued to cool over the last week. The NINO3.4 index value has dropped to –1.0 °C, the lowest value since January 2012 when the 2011-2012 La Niña event was decaying. The 30-day and 90-day values for the Southern Oscillation Index (SOI) have decreased over the past week with the latest values ending 25 October being +5.4 and +7.4. This decrease is most likely a short-term one due to lower pressure associated with the Madden-Julian Oscillation (MJO), which has been moving over the Maritime Continent during this period.

Surveyed international climate models predict La Niña will persist until at least February 2021. Climate models have continued to indicate further cooling is likely and that the current La Niña, based on sea surface temperatures (SST) across the tropical Pacific Ocean, may strengthen further. While La Niña and its associated impacts are unique from event to event, there is typically a relationship between the strength of the event and the strength of the impacts on Australia, such as increased rainfall.

The Indian Ocean Dipole (IOD) is neutral with the majority of surveyed climate models forecasting it will remain within neutral thresholds over the coming months. Only two of the six models suggest negative IOD thresholds may be reached in November though it is unlikely this will be for a period long enough to be considered a negative IOD event.

Read more about the El Niño-Southern Oscillation (ENSO)

Northern Australia likely to be wetter than average in coming months

The latest climate outlook from the Bureau shows an increased chance of above-average rainfall across most of Australia during November 2020–January 2021, with similar chances of above-average rainfall across northern Australia during December 2020–February 2021.

La Niña is typically associated with above-average rainfall across most of northern Australia during spring. During summer, above-average rainfall is mostly confined to eastern Queensland, although much of the Northern Territory and parts of far northern Western Australia typically observe marginally above-average rainfall. As a result, the 7-month northern wet season (October to April) normally sees above-average rainfall totals during La Niña.

Monsoon onset (at Darwin) is normally earlier during La Niña, with an average date around mid-December, compared to the average date of around 28 December.

Some parts of the northwest Northern Territory and the central coast of Queensland experienced their northern rainfall onset over the last week.

Madden–Julian Oscillation to move into the western Pacific Ocean

A strong pulse of the Madden–Julian Oscillation (MJO) is currently located over the eastern edge of the Maritime Continent. Most climate models suggest it will remain moderate to strong in strength and continue to move eastwards into the western Pacific Ocean over the coming days, before weakening in strength as it approaches Africa around the middle of November.

At this time of the year, the MJO brings increased westerly flow and rainfall to Northern Australia as it moves into the western Pacific Ocean.

Read more about the Madden–Julian Oscillation

Product code: IDCKGEW000

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

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