Tropical monitoring and outlooks
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.
Forecast MJO location and strength
The chart shows 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.
Tropical atmospheric waves
About tropical atmospheric waves
MJO
The Madden–Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. It can be characterised as an eastward moving pulse or wave of cloud and rainfall near the equator that typically recurs every 30 to 60 days.
Other tropical waves in the atmosphere
In addition to the MJO, other large-scale atmospheric waves also occur in the tropics. The main ones are the convectively-coupled Kelvin wave (KW), equatorial Rossby wave (ER), and mixed Rossby-Gravity wave (MRG). They can provide further insight into the current tropical weather, such as the location and development of tropical cyclones, and what may occur over the coming days to weeks. These waves occur year-round, but typically have a greater influence on tropical weather in the Australian region during the wet-season months of October to April.
Kelvin wave (KW)
Equatorial Kelvin waves are alternating low and high pressure centres along the equator that move from west to east. For consistency with the theoretical structure of Kelvin waves, convection (leading to cloudiness and rainfall) near the equator should be on the western side of the low pressure regions. In contrast, clear conditions should be found on the eastern side of the low pressure. Like other atmospheric tropical waves, alternating zones of cloudiness and clear weather can be seen on satellite imagery in association with an active Kelvin wave. The waves move in the same direction as the Madden–Julian Oscillation, from west to east, but typically 2 to 3 times faster.
Equatorial Rossby (ER) wave
In theory there are several different equatorial Rossby waves. The most commonly seen atmospheric ER wave, and the one we discuss here, has high and low pressure regions centred at latitudes about 10 degrees north and south of the equator. To be consistent with theory, the lows and highs should form a symmetric pattern about the equator. Due to the wind flow around these high and low pressure regions, some regions along the equatorial zone favour cloud and rain formation, while other regions favour stable, clear conditions. On satellite imagery equatorial Rossby waves can often be identified due to the presence of cloud systems at similar longitudes on both sides of the equator. These cloud systems, in conjunction with the off-equatorial low pressure, can be the precursors to tropical cyclones on either side of the equator. While equatorial Rossby waves move at a speed close to that of a typical Madden–Julian Oscillation pulse, they move in the opposite direction—from east to west.
Mixed Rossby-Gravity (MRG) wave
Like equatorial Rossby waves, mixed Rossby-Gravity waves also move towards the west, but MRG waves have their pressure centres arranged anti-symmetrically on either side of the equator. This means a low pressure centre on one side of the equator will be opposite a high pressure centre in the other hemisphere. Satellite analysis of mixed Rossby-Gravity waves shows favoured zones for deep convection, often with thunderstorm clusters, in an antisymmetric arrangement about the equator. Their speed of movement to the west is faster than that of an ER wave.
Images are from The COMET® Program, from Introduction to Tropical Meteorology.
The COMET® Website is at http://meted.ucar.edu/ of the University Corporation for Atmospheric Research (UCAR), sponsored in part through cooperative agreement(s) with the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce (DOC). © 1997–2021 University Corporation for Atmospheric Research. All Rights Reserved.
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.
Download data: RMM Data
*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.
Methodology: Until the end of 2013 we use the exact method of Wheeler and Hendon (2004, https://doi.org/10.1175/1520-0493(2004)132%3C1917:AARMMI%3E2.0.CO;2) and from 2014 we use the modified method of Gottschalck et al. (2010, https://doi.org/10.1175/2010BAMS2816.1).
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.
These maps show average minimum or maximum temperature anomalies for each of the 8 MJO phases. Red-yellow colours indicate higher than normal temperature, while blue colours indicate lower than normal temperature.
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.
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.
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
These maps show the atmospheric troughs and ridges (in blue and red, respectively) associated with the different phases of the MJO at the 500hPa level. The 500 hPa level is approximately 5500 m above sea level and is about the middle of the troposphere. Colour shading is only used where the geopotential height anomalies are determined to be statistically-significant at the 5% level.
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
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.
OLR totals over the dateline
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.
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
Australian region
Recent conditions
For the fortnight ending 5 January 2026, much of tropical northern Australia has seen heavy rainfall. The monsoon trough was situated over northern Australia for the first part of the fortnight, with the northern Australian monsoon onset, as measured at Darwin, occurring on 23 December 2025.
Northern Queensland experienced heavy to intense rainfall and thunderstorms as deep tropical moisture interacted with a monsoon low and an embedded trough over western Queensland, while further east, there was enhanced onshore winds along the north-eastern coast. These systems led to widespread flooding across the region.
Severe Tropical Cyclone Hayley (see below) made landfall as a Category 3 system on the Kimberley coast on 30 December 2025. It weakened to a tropical low by 31 December and tracked east across north-western Australia before dissipating.
Fortnightly totals of more than 100 mm were recorded across northern Australia, with totals exceeding 200 mm across much of northern Queensland and scattered areas of northern Western Australia and the Northern Territory. Widespread totals exceeding 400 mm were recorded across Queensland's Channel Country and adjacent inland areas, while along the Townsville coast localised totals exceeded 1000 mm.
The highest fortnightly total was 1353.8 mm at Cowley Beach (Defence) in Queensland, with most of this rainfall occurring in the week ending 5 January 2026. The highest daily total was 414.0 mm at Innisfail Wharf Alert in Queensland in the 24 hours to 9am on 31 December 2025.
Maximum temperatures were below average across large parts of northern Australia on most days during the past fortnight. Daily maximum temperature anomalies were up to 6 °C below average across large parts of the tropics, with some localised areas of western Queensland more than 12 °C below average on some days.
Fortnightly forecast
The forecast for the fortnight of 10 to 23 January 2026, issued on 5 January 2026, shows roughly equal chances of above or below average rainfall for much of the far north of Australia, with southern parts of the Northern Territory, and adjacent parts of Western Australia and Queensland likely to have below average rainfall for the fortnight. Some parts of Cape York Peninsula, and coastal areas of Queensland south of Bowen have an increased chance of above average rainfall for the fortnight, depending on the influence of the monsoon and tropical weather systems.
Madden–Julian Oscillation
The Madden–Julian Oscillation (MJO) is weak or indiscernible as of 3 January 2026. Most forecasts from surveyed models suggest that the MJO is likely to remain weak until around mid-January. Beyond this time, most models suggest the MJO is likely to strengthen in the Western Pacific region. This would likely weaken trade winds in the western Pacific, which could weaken the current La Niña event. It may also contribute to enhanced rainfall in parts of northern Australia.
Severe Tropical Cyclone Hayley
A low developed in the Indian Ocean to the north-west of the Kimberley, Western Australia, on 28 December. It rapidly intensified into Tropical Cyclone Hayley as it tracked southwards on 29 December. Hayley intensified to Category 4 strength as it turned eastwards towards the western Kimberley coast, north-west of Broome, with the system developing a clear eye early on 30 December. However, this feature was short lived, dissipating as the system experienced increasing wind shear as it approached the coastline. Severe Tropical Cyclone Hayley made landfall as a Category 3 system on the Kimberley's northern Dampier Peninsula on 30 December 2025. It had weakened to a tropical low by 31 December and subsequently tracked east across the Kimberley before dissipating.
Hayley marks the third tropical cyclone in the Australian region to reach Category 4 strength this season. This is the highest number of Category 4 systems by 5 January in a season since reliable records began in 1980–81.
Tropical Cyclone Iggy
Tropical Cyclone Iggy was a very short-lived tropical cyclone. It developed as a low to the south-west of the Indonesian island of Sumatra on 30 December, passing Christmas Island and strengthening as it moved south-eastwards towards Australia. On 1 January, the system developed into a Category 1 system and was named Iggy. However, by 2 January, Iggy had weakened back to a tropical low.
Tropical Cyclone Jenna
A tropical low in the eastern tropical Indian Ocean developed into Tropical Cyclone Jenna on 5 January 2026, just east of the Cocos (Keeling) Islands, tracking southwards. Late on 5 January, Jenna strengthened to a Category 2 system. Jenna is forecast to move to the south-west and intensify over the coming days, as it tracks away from the Australian region.
See the tropical cyclone 7-day forecast for the latest advice on systems in the Australian region.
Product code: IDCKGEW000
ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
Product Code: IDCKGEM000
