Surface weather analysis United States, temperature and dewpoint are plotted in degrees Celsius. The wind barb points in the direction from which the wind is coming. Each full flag on the wind barb represents of wind, each half flag represents . When winds reach , a filled in triangle is used for each of wind. In the United States, rainfall plotted in the corner of the station model are in inches. The international standard rainfall measurement unit is the millimeter. Once a map has a field of station models plotted, the analyzing isobars (lines of equal pressure), isallobars (lines of equal pressure change),
Atmospheric pressure m is the maximum height to which water can be raised using suction under standard atmospheric conditions. Low pressures such as natural gas lines are sometimes specified in inches of water, typically written as "w.c." (water column) gauge or "w.g." (inches water gauge). A typical gas-using residential appliance in the US is rated for a maximum of 14 w.g., which is approximately 1048.37hPa. Similar metric units with a wide variety of names and notation based on millimetres, centimetres or metres are now less commonly used. Pure water boils at at earth's standard atmospheric pressure. The boiling point is the temperature