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
*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)
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.
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.
Postscript: Coral Sea Dateline Fiji Guam & Marianas Indochina Malyasia & Indonesia Micronesia Nauru & Tuvalu New Guinea Northern Australia Philippines Solomon Island Southern India & Sri Lanka Vanuatu
Daily averaged OLR anomalies
Westerly wind anomalies
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.
Indian and South-East Asian monsoons remain active
A moderately strong Madden–Julian Oscillation (MJO), assisted by other tropical-wave activity, significantly enhanced tropical weather across the northern Indian Ocean and the western Maritime Continent during the last week.
Monsoonal flow has become well established over India and South-East Asia during the last fortnight. A monsoon trough which currently extends across the northern Indian Ocean to the northwest Pacific Ocean has become a focus for tropical activity. A tropical storm has developed over the Arabian Sea, while another weaker tropical low has formed to the northwest of the Philippines in recent days. Neither of these systems are expected to develop significantly in coming days. While the monsoonal flow persists, the risk of tropical cyclone development across this region remains enhanced.
Southern hemisphere Indonesia, which typically experiences its dry season at this time of the year, has been unseasonably wet. Over parts of central Java, rainfall of the order of 100 mm led to landslides which caused significant damage and multiple fatalities.
Most climate models forecast the MJO signal to weaken rapidly in the next few days before it reaches the western Pacific Ocean. The MJO is then likely to remain weak or indiscernible for the following week. Other tropical wave activity is also expected to reduce across the region in the coming week.
See the Bureau's MJO Monitoring for current MJO information.
Warm conditions likely to continue across northern Australia
The last week has seen a continuation of the warm conditions which have affected northern Australia for much of the year. The Bureau’s climate outlooks favour above-median daytime and overnight temperatures to persist over northern Australia. See: Climate Outlooks for more information.
Sea surface temperatures surrounding northern Australia remain much warmer than usual, contributing to the expected above-average temperatures across northern Australia in coming months.
ENSO Outlook remains atLa Niña Watch
While cooling of the tropical Pacific Ocean occurred during the last week, a neutral El Niño–Southern Oscillation (ENSO) continues. The Bureau’s ENSO Outlook remains at La Niña WATCH, which means around a 50 per cent likelihood of La Niña developing in the coming months.
Warmer waters in the Indian Ocean to the northwest of Australia, relative to the waters off the east African tropical coast, are maintaining a negative Indian Ocean Dipole (IOD)-like pattern. The latest weekly Dipole Mode Index (DMI) to 26 June has decreased to -0.9 °C and the DMI has remained below the negative IOD threshold of -0.4 °C for five consecutive weeks.
During negative IOD events Australia’s tropics typically experience warmer than average overnight temperatures during the dry season and the build-up to the wet season.
See the Bureau’s ENSO Wrap-Up for El Niño information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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