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This causes a mass accumulation that eventually leads to a vertical movement and to the formation of clouds and precipitation. [1] Large-scale convergence, called synoptic-scale convergence, is associated with weather systems such as baroclinic troughs , low-pressure areas , and cyclones .
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 ...
In most humid subtropical climates, summer is the wettest season. In summer, the subtropical high pressure cells provide a sultry southernly flow of tropical air with high dew points, and frequent (but brief) convective showers are common.
On weather maps, these areas show converging winds , also known as convergence, near or above the level of non-divergence, which is near the 500 hPa pressure surface about midway up through the troposphere, and about half the atmospheric pressure at the surface. [8] [9] High pressure systems are also called anticyclones.
A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form between the equator and the 50th parallel. [ 40 ]
Kona lows, most extratropical cyclones, and tropical upper tropospheric cyclones are cold core lows. In the eastern half of the north Pacific Ocean and north Indian Ocean, the formation of a weak circulation underneath a mid to upper-tropospheric low which has cut off from the main belt of the westerlies during the cold season is called a subtropical cyclone.
Clouds dissipating in the subtropical ridge. An important atmospheric ridge is the subtropical ridge . It is a series of ridges near the horse latitude characterized by mostly calm winds, which act to reduce air quality under its axis by causing fog overnight, and haze during daylight hours as a result of the stable atmosphere found near its ...
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 ...