The MJO is due north of Australia early November. This could mean the first incursion of the rainy season (but NOT the monsoon) for much of northern Australia.
The monsoon might then be intiated be the next passage of the MJO, early-mid December.
The MJO is currently weak, but in the region of Phase 1. Phase 1 and 2 are associated with drier conditions in northern Australia during summer.
Fewer weak MJO signals occur during Austral (southern) summer. Phases 4-7 are associated with increased chances of rain across the north of Australia.
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Hi Lexie,
Thanks again for your insightful analysis.
What circumstances contributes to a deep MJO?
Certainly here in the north (Darwin) we are feeling the effects of see-sawing sst's and a pathetic MJO :(
Hi Paul
A deep MJO?
Deep convection, with divergence well aloft (tropopause) and easterly flow and more substantial westerley flow convereging into the convection base, plus the distinctive eastward velocity, and super cloud clusters, with internal cloud clusters that may degrade westward (rather than to the east).
Hiya Lexie,
Thanks for that. So it's believed that the MJO originates from the African continent?
How & why?
Howdy Paul
MJO - its a bit more complicated , but essentially: yes.
A wave comes across Africa, hits the nice warm Indian Ocean, gets moist, convection develops, and the speed of the wave is slowed to the characterisitc periodicity when it goes from dry to wet. The convection is slightly baroclinic, that is its tilted, and the divergence at the top of convection trails (is westward) of the convection base.
The MJO does actually go right around the equator, but is only moist mostly in the eastern hemisphere - it dries out somewhere mid- Pacific, then it speeds up, is connected with hurricanes in the Atlantic, crosses Africa.... and goes around again.....
So the Bureau's RMM Phase system is centred on the active convective regions for MJO, from Africa to the date-line.
Thanks Lexie - that was my limited understanding of the beast that is the MJO.
Do we know what causes the planetary wave in the first place? is it mass subsidence of air associated with mid-latitude high pressures on the African continent; perhaps associated with the Sahara?
gravity wave - planetry rotation plus any other causes you care to think of
So essentially it's a broadscale perturbation in the fluidic movement of the atmosphere?
Often you can observe gravity waves originating from storm complexes over Northern Australia, moving out into the Timor, Arafura & SIO.
Similar?
similar? Yep sure but BIGGER.
Like a freight train (MJO) cf
semi-trailer (storm track)- and I don't mean one of those giant scarey NT road trains!
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