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.

Slight weakening of positive Indian Ocean Dipole

The positive Indian Ocean Dipole (IOD) weakened marginally during the past week. This is likely due to interference with the Madden–Julian Oscillation as it moved over the eastern Indian Ocean and therefore unlikely to be an indication of the imminent decay of the positive IOD. The most recent weekly value of the IOD index was +1.7 °C, down from +2.0 °C the previous week. The threshold for a positive IOD is a sustained value of +0.4 °C or greater, so the current event remains strong.

The influence of the positive IOD is reflected in the latest rainfall outlook issued by the Bureau, which indicates a high likelihood of below-average rainfall for much of northern Australia for the remainder of November and throughout December. The positive IOD is also likely to lead to a delay in the onset of the Australian monsoon in 2019-20. Climate models surveyed by the Bureau indicate the positive IOD is so strong that its breakdown is likely to take longer than usual. The decay of the IOD is associated with the seasonal development of a monsoon trough in the southern hemisphere around December, but this process is well behind its typical schedule and is likely to happen significantly later than usual in 2019. As a result, the influence of the IOD is expected to persist into January 2020.

Read more about the Indian Ocean Dipole.

Madden–Julian Oscillation maintains strength over Pacific Ocean

A moderate to strong pulse of the Madden–Julian Oscillation (MJO) is rapidly tracking eastwards across the tropical Pacific Ocean. Climate models predict the MJO will track from the central to eastern Pacific Ocean in the coming week and then approach the Americas in the following week. At this time of the year, an MJO pulse over the central Pacific Ocean would typically enhance rainfall over parts of northern Australia and the southern Maritime Continent. However, due to the rapid movement of the MJO pulse and the adverse local environment associated with the positive IOD, the presence of the MJO is unlikely to lead to widespread above-average rainfall. As the MJO moves over the eastern Pacific Ocean, and further east, cloudiness and rainfall across northern Australia, the Maritime Continent and much of South-East Asia is typically suppressed. The combination of the positive IOD and the suppressed component of the MJO increases the likelihood of below-average rainfall occurring across the Australian tropics in the coming fortnight.

Read more about the Madden–Julian Oscillation.

Two tropical cyclones impact Asia in recent days

Tropical storm Nakri made landfall on the southeast Vietnam coast during Monday morning, generating locally heavy rain and strong winds. Nakri weakened to below-typhoon strength (Australian category 3 equivalent) prior to reaching the coast of Vietnam. Nakri has weakened to below tropical cyclone intensity.

Cyclonic storm Bulbul, which formed from the remnants of ex-tropical storm Matmo, made landfall over West Bengal, in northeast India, on Monday night and then moved over Bangladesh. A dangerous storm surge, heavy rainfall and damaging wind gusts occurred as Bulbul moved ashore. This storm has now dissipated and adverse weather conditions in the area have eased. Bulbul peaked at hurricane strength (equivalent to a typhoon, or Australian category 3 or greater system), making it the sixth storm of such intensity to develop over the northern Indian Ocean in 2019. This is the highest number of hurricane-strength storms ever recorded in this region in a single season.

Two other developing tropical lows over the western North Pacific Ocean have the potential to develop into tropical cyclones in the next day or two. While one system is over open waters well to the southeast of Japan, the other low is just to the east of the Philippines and forecast to move towards the island group in the short term.

 Tropical cyclone information for this region available at the Japan Meteorological Agency.

Product code: IDCKGEW000

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

Product Code: IDCKGEWWOO