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
*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)
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.
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.
Postscript: Coral Sea Dateline Fiji Guam & Marianas Indochina Malyasia & Indonesia Micronesia Nauru & Tuvalu New Guinea Northern Australia Philippines Solomon Island Southern India & Sri Lanka Vanuatu
Daily averaged OLR anomalies
Westerly wind anomalies
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.
Weekly Tropical Climate Note
Issued 24 February 2015
Two severe tropical cyclones hit Australia
Over the past week, two severe tropical cyclones made landfall on the Australian coastline within hours of each other. Both storms crossed the coast on Friday 20 February. Severe tropical cyclone Lam made landfall on the north coast near the small town of Milingimbi in the Northern Territory at around 2:00 am (local time). Severe tropical cyclone Marcia made landfall on the central Queensland coast near 8:00 am (local time). This marks the first time in recorded history that two severe tropical cyclones crossed the Australian coast line on the same day.
The Madden-Julian Oscillation (MJO) has been weak or indiscernible in recent weeks and is not likely to have influenced tropical activity during this period. Rather, the recent increase in monsoonal weather and tropical cyclone activity in the Australian region is likely to have been influenced by a slow moving tropical disturbance, called an equatorial Rossby wave. These waves move slowly westwards and act to temporarily enhance tropical cloud and rainfall as they pass over a region. These waves often create a pair of low pressure circulations that form within the same longitude but on opposite sides of the equator.
Madden–Julian Oscillation likely to remain weak
Climate model forecasts for the MJO provide two possible scenarios for the coming weeks. The first, and most likely, scenario is that the MJO will remain weak or indiscernible for the next two weeks and hence will be unlikely to influence tropical weather patterns. The second scenario is that the MJO will gain strength over the Maritime Continent within the next seven to ten days, and therefore increase the chances of convection and tropical cyclone activity over the Australian region again.
See the Bureau's MJO Monitoring for more information.
El Niño–Southern Oscillation neutral
Sea surface temperatures across the tropical Pacific Ocean are neutral, having eased away from near–El Niño levels experienced late last year. The latest weekly NINO3.4 sea surface temperature anomaly is +0.43 °C and the 30 day SOI to 22 February is +0.8, the highest value since June 2014. Models indicate that tropical Pacific sea surface temperatures are likely to remain warm, but within the neutral range, until at least May. Several models suggest some warming may occur beyond May. However, model outlooks made in the first quarter of the year tend to be less reliable than those made at other times. This is because it is this time of year when ENSO events naturally decay. That said, all international models surveyed by the Bureau are consistent.
See the Bureau of Meteorology's ENSO Wrap up for official El Niño information.
Next update expected by 17 February 2015 | Product Code IDCKGEW000
ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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