Pressure system low pressure, while As depict anticyclonic flow or likely positions of high-pressure areas. An area of confluent streamlines shows the location of shearlines within the tropics and subtropics. Pressure system A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in upper levels of the troposphere. The formation process of a low-pressure area is known as cyclogenesis. Within the field of atmospheric dynamics, areas of wind divergence aloft occur in two areas: Diverging winds aloft ahead of these troughs
High-pressure steam locomotive sealed ultra-high-pressure circuit that simply transferred heat to a high-pressure circuit, by means of heating coils inside a high-pressure boiler. If this latter was fed with ordinary water, scale could form on the outside of the heating coils, but it could not cause overheating because the ultra-HP tubes were quite capable of withstanding their internal steam temperature, though not the firebox flame temperature. The sealed ultra-high-pressure circuit ran at between , depending on the rate of firing. The HP boiler worked at approx , and the low-pressure boiler at . The UHP and HP boilers were of a water tube