Page History

...

Inspection of Hovmoeller and Wheeler-Hendon diagrams can give a guide towards the consistency and intensity of an MJO event.  The distortion of the upper flow associated with an MJO affects monsoon activity and, equally important, modifies the northern and southern hemisphere mid-latitude jets, impacting on predictability of extratropical extra-tropical patterns. This can be expressed in terms of weather regime impacts. 

...

The forecast based on 00UTC 25 Feb 2019 illustrates the tele-connection effect of tropical deep convection over the Indian Ocean upon subsequent downstream developments of NAO+ type over the North Atlantic/Europe. 

Image RemovedImage Added

Fig8.2.8-4: Meteosat (IODC) IR (Channel 4) image DT 00UTC 25 Feb 19.  A large area of convection lies over an equatorial region of the Indian Ocean typical of Madden-Julian Oscillations (MJO

Image Removed

Fig8.2.8-5: MJO Wheeler-Hendon diagram for the monthly forecast based on DT 00UTC 25 February 2019.   The colours represent ENS forecasts at various lead times as given by the key above the diagram.  Initially the MJO lies within Sector1 (Western Indian Ocean) and is forecast to progress into Sector2 (Eastern Indian Ocean) by Day5 with a fairly limited spread among ENS members. The mean position of the ENS forecasts during the subsequent ten days show continuing westward progress although with an increasing spread before weakening (moving into the central circle) by Day20.

...