Madden-Julian Oscillation (MJO)


MJO phase diagram

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*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)

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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.

Fewer tropical cyclones likely this season for Australia

The Bureau of Meteorology has released its Australian tropical cyclone outlook for the season which runs from November 2019 to the end of April 2020. The outlook predicts that fewer than the long-term average of eleven cyclones will form in the Australian region this coming season. Northern Australia typically sees four tropical cyclones make landfall each season, so all coastal communities in Australia's tropics have a significant risk of being impacted by a tropical cyclone in any given year.

The dominant climate influence for Australian tropical cyclone activity is typically the El Niño-Southern Oscillation (ENSO); during El Niño years less than average cyclone numbers are typically observed, while in La Niña years, there are typically more than average. Despite sea surface temperatures in the tropical Pacific Ocean indicating a neutral (neither El Niño or La Niña) ENSO phase, the Southern Oscillation Index (SOI) has remained close to El Niño-like levels for much of the last three months. This is due to above-average pressure at Darwin, likely related to the ongoing strong positive Indian Ocean Dipole (IOD) event, and is a factor contributing to the below-average assessment for tropical cyclone activity in 2019-20.

Late withdrawal of the Indian monsoon

The Indian Meteorological Department recently stated that the retreat of the Indian southwest monsoon from northern India commenced on 9 October. This is the latest date on record; the previous latest date was 1 October 1961— also a positive IOD year— and much later than the average date of 1 September. The Indian monsoon was the strongest in recent years with above-average rainfall in 2019, in part due to the contribution of the positive IOD. Climate models currently indicate the positive IOD may persist longer than typical events do, and the delayed transition of the monsoon trough from the northern hemisphere to the southern hemisphere may be a related factor. A positive IOD which persists later than usual may also contribute to a delay of the onset of the Australian monsoon this season.

Typhoon Hagibis strikes Japan  

Typhoon Hagibis made landfall to the southwest of Tokyo last Saturday with sustained winds in excess of 150 km/h (equivalent to an Australian category 3 severe tropical cyclone) and generated extremely heavy rainfall which led to widespread flooding and landslides. Hagibis has been described by international media reports as Japan's biggest storm in decades. Hakone, a town east of Mount Fuji, had a 24-hour rainfall total of 942.5 mm, which is one of the highest daily rainfall totals ever recorded in Japan. There have been unofficial reports of daily totals in excess of 1000 mm which, if confirmed, would be the highest on record for Japan. Hagibis caused major damage in Japan, with reports of multiple fatalities, missing people, and significant damage to property. Hagibis was downgraded to below-tropical cyclone intensity during Sunday and is not expected to re-intensify.

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

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