MJO. the madden julian oscillation.
there are a couple of things i understand about it, if only in a layman sense.
mjo is an inhibiting/enhancing factor in convective activity in the tropics.. its positive phase causes anomolously poor conditions at outflow levels for intense convection, while its negative phase is often timed with bursts of tropical cyclone activity in whatever basin it happens upon.
the wave is a high altitude feature, it occurs at outflow levels.. and i'm not certain, but do believe its relative strength and effect on global weather patterns is related to the monsoon down there.. which is itself linked to various other factors. it comes more in an amorphous patch than a wave, as it propagates eastward around the globe.. pulsing and deforming its coverage area... but i'd imagine if plotted on an graph it's would appear as a waveform.
this doesn't seem to be the year to get in to how much of an effect mjo has had.. because it has been pronounced at times (fabian, grace,henri, isabel, and td14 came about during a recent passage, after a erika and a mere depression over the previous month).. but not as much as in certain recent years. if another arrives at what seems to be the regular interval for the season.. we should get another burst of activity in mid-october. right now mjo conditions appear neutral to negative for most of the basin.. the rest of september will probably be fairly quiet, aside from that large hurricane currently out still out there.
HF 1525z13september