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),
Pressure altitude Pressure altitude Pressure altitude within the atmosphere is the altitude in the International Standard Atmosphere (ISA) with the same atmospheric pressure as that of the part of the atmosphere in question. The National Oceanic and Atmospheric Administration (NOAA) has published the following formula for directly converting atmospheric pressure in millibars (formula_1) to pressure altitude in feet (formula_2): In aviation, the pressure altitude is the indicated altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances in which the aircraft’s altimeter would be unable to give a useful readout of the altitude. Examples would be landing