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An example of a convergence zone is the Intertropical Convergence Zone (ITCZ), a low pressure area which girdles the Earth at the Equator. [3] Another example is the South Pacific convergence zone that extends from the western Pacific Ocean toward French Polynesia.
Some tropical or subtropical regions such as the Philippines or South China are greatly affected by convection cells along a trough. In the mid-latitude westerlies, upper level troughs and ridges often alternate in a high-amplitude pattern. For a trough in the westerlies, the region just west of the trough axis is typically an area of ...
Occasionally, cyclogenesis will re-occur with occluded cyclones. When this happens a new low center will form on the triple-point (the point where the cold front, warm front, and occluded front meet). During triple-point cyclogenesis, the occluded parent low will fill as the secondary low deepens into the main weathermaker.
Depth of 26 °C isotherm on October 1, 2006. There are six main requirements for tropical cyclogenesis: sufficiently warm sea surface temperatures, atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to sustain a low-pressure center, a preexisting low-level focus or disturbance, and low vertical wind shear. [3]
Mesoscale convective systems, which can evolve into tropical cyclones, form along areas such as tropical waves or easterly waves which progress westward along monsoon troughs and the Intertropical Convergence Zone in regions of ample low level moisture, convergent surface winds, and divergent winds aloft.
The documented shift and expansion of subtropical ridges are associated with changes in the Hadley circulation, including a westward extension of the subtropical high over the northwestern Pacific, changes in the intensity and position of the Azores High, and the poleward displacement and intensification of the subtropical high pressure belt in ...
This mid-level circulation is referred to as a Mesoscale Convective Vortex. The upper-levels contain an anti-cyclonic (clockwise in the Northern Hemisphere) rotating high pressure which is a sign of divergence of air. This high pressure is colder relative to its surrounding environment.
When the subtropical disturbances in the Northern Hemisphere actively move southward, or dig, the area between the upper tropospheric anticyclone to its west and cold-core low to its east generally have strong northeasterly winds in addition to a rapid development of active thunderstorm activity. Cloud bands associated with upper tropospheric ...