Madden-Julian Oscillation (MJO)

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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 is 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.

Tropical Climate Note

Issued on Tuesday 14 October 2014

Tropical cyclone activity

This past week has seen tropical convection mainly focused over the Bay of Bengal, parts of India and over the northwest Pacific Ocean.

Very severe cyclonic storm Hudhud, which developed to cyclonic storm strength on 8 October, became the strongest storm to form over the Bay of Bengal this year. Hudhud moved slowly northwest and developed rapidly, reaching peak strength shortly before making landfall near Visakhapatnam, Andhra Pradesh, India on Sunday 12 October.

The main focus of the tropical activity in the northwest Pacific Ocean was associated with typhoon Vongfong (Ompong). Typhoon Vongong reached Category 5super typhoon strengthlast week, becoming the most powerful cyclone of 2014 to date. Typhoon Vongong impacted Japan over the weekend, but had weakened significantly before impact.

Madden-Julian Oscillation

Recent cyclone activity over the west Pacific Ocean and Bay of Bengal is unlikely to have been influenced by the Madden-Julian Oscillation (MJO) as little or no MJO signal has been detected during the past week. While the MJO often contributes to intraseasonal variability of global monsoon systems other sources of variability also influence global monsoon patterns. Warm sea surface temperatures and favourable atmospheric conditions this past week have increased the risk of tropical cyclone development over these regions.

Most climate models indicate a new burst in MJO activity may develop and strengthen over the western hemisphere and Africa in the next two weeks; however, the strength of the MJO signal is uncertain. If the MJO strengthens over Africa it may act to supress activity over the northwest Pacific and hence reduce the risk of tropical cyclone activity.

See the Bureau's MJO Monitoring for more information on the location and tracking of the MJO.

El Niño—Southern Oscillation in neutral state

While the Pacific Ocean continues in an ENSO-neutral state, persistent warmth in the tropical Pacific Ocean and a recent weakening of the trade winds in the west equatorial Pacific may provide some further warming towards El Niño thresholds. Recent observations and model outlooks indicate there remains a 50% chance of El Niño developing during the last quarter of 2014. The latest NINO3.4 sea surface temperature anomaly is +0.5°C. The latest Southern Oscillation Index value is -3.5.

See the Bureau of Meteorology's ENSO Wrap up for official El Niño information.

Tropical Cyclone Outlook

El Niño conditions usually decrease overall tropical cyclone activity around Australia. For the Australian tropical cyclone season ahead, average to below average tropical cyclone activity is most likely for the Australian region. The Australian tropical cyclone season runs from November to the end of April and there is always a risk of tropical cyclone development even in El Niño years.

Next update expected by 21 October 2014| Product Code IDCKGEW000

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

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