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The Madden-Julian Oscillation affects the North Atlantic Oscillation.   The mid-latitude jet streams in turn can affect the flow over the North Atlantic which has a strong impact on the tracking of depressions (e.g. towards Europe).  The cross-Atlantic flow can be categorised as positive or negative phases or regimes of the North Atlantic Oscillation (NAO).

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Wheeler-Hendon MJO diagram

The Wheeler-Hendon MJO index plot displays the time evolution, location and magnitude of the MJO predicted by ensemble and described by a multivariate MJO index (Wheeler and Hendon 2004 Mon. Wea. Rev. vol. 132, 1917-1932).  The magnitude of the MJO is essentially proportional to the distance of the point from the centre of the diagram.  (Current MJO Index Plot)

Fig8.2.5-5: Wheeler-Hendon MJO diagram.  Time evolution of the MJO as predicted by the ensemble using zonal winds at 850hPa, 200hPa velocity potential and simulated OLR, all averaged between 15S and 15N.  Individual ensemble member values at day 1, 5, 10, 15 and 20 are represented respectively by red, pink, orange blue and green circles. The ensemble mean values (black triangles) are joined by a solid black line, and the analysis values of the preceding 30 days are joined by a grey line (with grey dots added every 5 days).  Points representing sequential values trace anti-clockwise trajectories around the origin,indicating systematic eastward propagation of the MJO.  Large amplitudes (outside of the circle) signify strong cycles of the MJO, while weak activity appears as rather random motion near the origin. The phases (broadly geographical regions) are numbered 1 to 8.  See Wheeler and Hendon 2004 Mon. Wea. Rev. vol. 132, 1917-1932 for details.

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