Tropical monitoring and outlooks
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.
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

Heavy rainfall across northern Queensland
Tropical low 13U brought several days of widespread heavy rainfall to Queensland's northeast tropical coast. Between Ayr and Cairns, many sites recorded weekly rainfall in excess of 700 mm, with the highest weekly rainfall total (to 3 February) at a Bureau gauge recorded at Cardwell Range with 1697.0 mm which also recorded the highest daily rainfall total for this week, with 626.0 mm in the 24 hours to 9 am on 3 February.
Several days of heavy rainfall has led to flash and riverine flooding. As at 4 February Major Flood Warnings were in place for several catchments in the region, including the Haughton, Herbert, and Upper Burdekin rivers. There were also further Minor to Moderate Flood Warnings. The flooding has had major impacts on roads, including the collapse of the Ollera Creek Bridge between Townsville and Ingham, limiting supply routes to Ingham. The Burdekin Falls Dam is at 173% capacity as at 4 February.
Many sites across northern Queensland have recorded their highest daily or multi-day rainfall totals on record. Rainfall in the region is comparable in magnitude to that observed during the 2019 event. Rainfall is forecast to ease over the coming days.
For the fortnight beginning 8 February, rainfall is likely to be above average across most of the northern half of the Northern Territory and Queensland. Most of Cape York Peninsula is very likely (greater than 80% chance) to receive above average rainfall during the fortnight. Increased cloud cover means that maximum temperatures are likely to very likely to be below average across most of the Cape York Peninsula and western Queensland. Nights are likely to very likely to be warmer than average across northern Australia.
Tropical cyclone activity in Australian region
There was increased tropical activity in the Australian region during the week ending 4 February. A total of 4 systems reached at least tropical low strength (13U, 14U, 15U, 16U). The last time there was near-simultaneous development of 4 systems in the Australian region was at the end of January 2014. Tropical Cyclone (TC) Taliah (14U) and Tropical Cyclone Vince (15U), are both currently at Category 3 (Severe) strength. Severe TC Taliah is expected to move westwards, away from the Australian region. Severe TC Vince is located south-west of the Cocos (Keeling) Islands (as at 4 February) and is forecast to move west-south-west. Severe TC Vince and Severe TC Taliah are not expected to impact the Australian mainland or island communities.
Tropical low 16U is currently, as at 4 February, south of the Solomon Islands. It is forecast to track south then south-east, away from the Australian region, and is unlikely to directly impact the Australian mainland.
For the latest details on tropical low and tropical cyclone development, check the Tropical cyclone 7 day cyclone forecast and the Fiji Meteorological Service Tropical Cyclone outlook.
Monsoon trough over Queensland, but not yet near Darwin
The lack of monsoon activity, combined with high sea surface temperatures and onshore winds, have led to high temperatures and dewpoints in the Darwin region. Darwin Airport recorded its highest February minimum temperature on record on 3 February, 30.0 °C. This was also the equal second-highest minimum temperature for any month in its 85-year record.
Despite increased tropical activity in the past week, the criteria for the onset of the monsoon in Darwin are yet to be met, as at 4 February. Monsoon troughs are evident north-west of the Australian coast from Severe TC Vince to east of Severe TC Taliah, and over the Gulf of Carpentaria and Far North Queensland.
Monsoonal conditions are forecast along the north coast of the Northern Territory's Top End later this week, with a corresponding increase in rainfall and cloudiness, and a general decrease in temperatures, especially in coastal areas. A monsoon trough may form south of Darwin over 8 to 9 February. When the monsoon onset criteria are met at Darwin Airport, it will be the latest recognised onset date on record. The previous latest monsoon onset recorded at Darwin since records began in 1957–58 was during the 1972–73 wet season, on 25 January 1973.
Madden–Julian Oscillation approaching the Western Pacific
A moderate to strong pulse of the Madden–Julian Oscillation (MJO) has progressed across the Maritime Continent during the week ending 3 February and is now approaching the Western Pacific. The pulse weakened slightly in the last week. As the MJO progresses across the western Pacific, there is a spread of likely strength from surveyed models. Some models, including the Bureau's, forecast the MJO pulse to become indiscernible during February as it enters the Western Pacific while others forecast weak to moderate strength of the MJO in the Western Pacific.
Product code: IDCKGEW000
ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
Product Code: IDCKGEM000