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 location and strength

These graphs show the strength and progression of the MJO through 8 different areas along the equator around the globe.
Area 3 is north west of Australia, 4 and 5 are to the north (the Maritime Continent), and 6 is to the north east.

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 this index is within the centre circle the MJO is considered weak. 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.

MJO phase diagram
MJO phase diagram

*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.

Average weekly rainfall probabilities

These maps show average weekly rainfall probabilities for each of the 8 MJO phases. Green shades indicate higher than normal expected rainfall, while brown shades indicates lower than normal expected rainfall.

Select the 'Wind' checkbox to also show the expected 850 hPa (approximately 1.5 km above sea level) wind anomalies. 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 global weather patterns changes with the season.
Read more: The Combined Influence of the Madden–Julian Oscillation and El Niño–Southern Oscillation on Australian Rainfall.

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.

Maps of total and anomaly outgoing longwave radiation (OLR)

Regional maps of outgoing longwave radiation (OLR)

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.

Tap boxes to view a timeseries graph of cloudiness for that region
image/svg+xml Southern India and Sri Lanka Southern India and Sri Lanka Indochina Indochina Philippines Philippines Malaysia and Indonesia Malaysia and Indonesia Guam and Marianas Guam and Marianas Micronesia Micronesia Northern Australia Northern Australia Coral Sea Coral Sea Vanuatu Vanuatu Fiji Fiji New Guinea New Guinea Solomon Islands Solomon Islands Nauru and Tuvalu Dateline Dateline

OLR totals over the dateline

OLR totals over the dateline (area at far right in region map above)

Time longitude plots

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.

Daily averaged OLR anomalies

Westerly wind anomalies

Dry conditions expected to continue across northern Australia

Weather typical of the northern Australian dry season has arrived across the northern tropics over the last fortnight, with dry weather and low humidity present across the region. These conditions are expected to continue over the coming fortnight. Ridges of high pressure in the southern latitudes are resulting in easterly winds bringing surges of dry air to the north.

Tropical cyclone activity over the Indian Ocean

As dry season conditions become further established over northern Australia, increased tropical activity is moving further north into the northern hemisphere. Tropical wave activity, predominantly due to the Madden–Julian Oscillation and Kelvin waves, is leading to enhanced tropical weather in the near-equatorial zone, affecting a region which extends from the central Indian Ocean to parts of the Southwest Pacific.

This tropical activity, extending from Papua New Guinea to near the Indian subcontinent, contributed to the formation of severe tropical cyclone (TC) Mocha. This storm formed over the Bay of Bengal before crossing the coast of Myanmar on Sunday 14 May 2023 as a category 4 system, impacting both Myanmar and neighbouring Bangladesh. At its peak over the weekend, TC Mocha produced sustained winds of just over 280km/h and resulted in extensive damage to communities in low lying coastal areas, and reportedly 29 deaths. TC Mocha has since been downgraded to below TC strength.

TC Fabian also formed in the Indian Ocean and is currently classified as a severe category 3 system. It is currently located approximately 285nm east-northeast of Diego Garcia Island in the Indian Ocean and is a slow-moving system. TC Fabian is expected to track southwest, passing south of Diego Garcia Island by the middle of this week. It is expected to continue to intensify, but remain as a Category 3 system, before it starts to weaken towards the weekend over open waters.

Madden–Julian Oscillation in the western Pacific

The Madden–Julian Oscillation (MJO) pulse is currently over the western Pacific region and is expected to remain in that region during the next fortnight. At this time of year, the MJO has little influence on rainfall patterns across northern Australia. Further north, an MJO in the western Pacific means suppressed rainfall is more likely for the eastern and central Indian Ocean near and north of the equator, along with the western Maritime Continent region. Additionally, it may also weaken Pacific trade winds and assist development towards an El Niño state.

Read more about the Madden–Julian Oscillation and Climate Driver Update

Product code: IDCKGEW000

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

Product Code: IDCKGEM000

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