Forming from the near-equatorial trough, the system moved generally to the southwest, dissipating on September 27 as it approached Mauritius.
2.
In summer, the equatorial trough normally positioned about 5�N of the equator moves over the Ganga plain creating a monsoon trough during the monsoon season.
3.
Less than a month later, another area of convection developed within the near-equatorial trough near the Chagos archipelago, due to persistent warm water temperatures.
4.
During January 14, the JTWC started to monitor an area of convection that had developed within the near equatorial trough of low pressure, about 900 km ( 560 mi ) to the southeast of Colombo, Sri Lanka.
5.
The upper-level divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft . As the air moves towards the Mid-Latitudes, it cools and sinks, which leads to subsidence near the 30th parallel of both hemispheres.
6.
The page Subtropical ridge hints at a bit more : " The divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft . As it moves towards the Mid-Latitudes, the air cools and sinks, which leads to subsidence near the 30th parallel of both hemispheres . " The impression I get from reading these, and other pages, is that the Hadley cells and the polar cells are the driving forces, while the in-between mid-latitude Ferrel cell exists mainly because the polar and Hadley cells have a gap between them.
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