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

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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.

Warm conditions likely for start to northern wet season

Northern Australia recorded the warmest daytime temperatures on record for June to August. The Bureau of Meteorology's 'first look' climate outlook for October to December also suggests warmer than average daytime and night-time temperatures are likely to continue across northern Australia. Northern Australia is the area north of 26°S latitude - which is roughly in line with the Northern Territory/South Australia border.

Across northern Australia, the build-up to the monsoon usually takes place from October to December as isolated afternoon thunderstorms gradually become more frequent. The outlook for this year's build-up (October to December) indicates equal chances of above- or below-average rainfall for most of northern Australia. The temperature outlooks show above-average daytime and overnight temperatures are likely. The rainfall prognosis is likely the result of competing influences between the Pacific and Indian oceans, with a weak drying influence from the Indian Ocean potentially cancelling out a slightly wet influence from the Pacific Ocean. The warmer conditions are consistent with the global trend of increasing atmospheric and oceanic temperatures, also the forecast warmer-than-average sea surface temperatures to Australia's north.

Typhoon activity persists in the northwest Pacific Ocean

Typhoon Talim (Lannie), the sixth typhoon in the northwest Pacific region for 2017, passed over the Ryukyu Islands of Japan, including Miyako-Jima, before making landfall on the southern Japanese island of Kyushu on 17 September. Talim (Lannie) had weakened to tropical storm strength by the time it hit Kyushu, but Shimoji Airport on Miyako-Jima recorded typhoon-strength sustained winds of 140 km/h and peak gusts to 183 km/h. Talim (Lannie) generated very heavy rainfall which led to mass evacuations in southern Japan in recent days, and earlier in parts of China. Parts of Kyushu recorded over 500 mm of rain in a 4-day period, while Shimoji Airport had 515 mm in a 2-day period and a 24-hour total of 479 mm – the heaviest falls at the site since 1977.

The seventh typhoon of the season made landfall on the central eastern coast of Vietnam within 24 hours of Talim (Lannie). Typhoon Doksuri (Maring) had sustained winds of around 135 km/h when it crossed the Vietnamese coast. Its winds caused widespread damage to houses in the region. Heavy rainfall associated with the storm generated flooding and landslides, leading to mass evacuations in some central provinces of Vietnam.

There have now been eighteen named storms across the northwest Pacific Ocean in 2017, close to the average of just under seventeen.  The seven typhoons during the season to date are less than the long-term average of ten. Tropical cyclone activity typically lessens over the northwest Pacific at this time of the year, but tropical cyclones can occur during all months in this part of the world.

Madden–Julian Oscillation expected to weaken

The Madden–Julian Oscillation (MJO) signal recently strengthened marginally in the western Indian Ocean. The increase in amplitude is expected to be short-lived, as all climate models surveyed by the Bureau predict the MJO signal will become weak in the next day or two and remain that way for the coming seven days.

The recent MJO activity coincided with a re-invigoration of the Indian Southwest Monsoon, which strengthened in response to a tropical low over the Bay of Bengal (likely the remnants of Doksuri (Maring)). If the MJO signal becomes weak, as forecast, it will not be a significant influence on tropical rainfall or temperature patterns in the coming week.  The Southwest Monsoon would also typically weaken and resume its withdrawal from the Indian subcontinent at this time of year.

See the Bureau's current MJO monitoring for more information.

Product code: IDCKGEW000

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

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