Analysis - MJO: what is it and why do we watch it?
/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 Explainer
Click on the image to play this 3-minute MJO explainer
Predicting the MJO and where is it now?
Due to its slowly evolving nature, accurate prediction of the MJO is fundamentally related to scientists ability to monitor the feature and to assess its relative position and strength. Dynamical models generally do not predict the MJO well, partly because of the inherent difficulties that still remain regarding the correct mathematical treatment of tropical convective (rainfall) processes. Meteorologists use a variety of data and analysis techniques to monitor, study, and predict the formation and evolution of the MJO.
In the chart below;
The black line is observations with dates (where it is now is largest black dot #21)
The yellow lines are potential modelled outcomes (bracketed by shading)
The green line is the median prediction (where to next)
The phase is its location: Australia generally 5-6
The strength is indicated by where it is plotted: inside the circle = weak. Outside the circle = stronger. The closer to the outside, the stronger the pulse.
So what?
Dynamical models favour little to no MJO activity during Week-1 (22-29 Dec) but suggest potential renewed MJO activity over the Indian Ocean during Week-2 (30 Dec-6 Jan).
Given the current weak signal, the MJO is unlikely to substantially influence the tropical convective pattern or subsequent extratropical response. The ongoing La Niña remains the primary tropical convective driver (see the latest NCEP conditions report).
The weaker MJO may reduce tropical moisture but it has a silver lining - a strong MJO in phases 8-1 can bring on heat waves which we can do without!