Decoding Guide

Surface Analysis Chart


This chart depicts the location of fronts, troughs, and instability lines, along with high and low pressure centers.


This product is a combination of a Surface front plot (yellow), and a MSL Isobar plot (white). The Isobar plot depicts the current positions of surface highs and lows, and mean sea level pressure over North America. The surface front plot is an analysis showing the current location of surface fronts, troughs, and instability lines. Tropical cyclone positions are included as appropriate.


0000, 0300, 0600, 0900, 1200, 1500, 1800, and 2100 UTC

Data Sources:

Surface observations, Radar and Satellite observations


The isobar plot, colored in white, shows the location of high and low pressure centers. High and Low pressure centers are depicted using Surface Analysis and Surface Analysis symbols. White contour lines (in intervals of 4mb) indicate areas of uniform pressure. Pressure values appear close to the pressure center symbol or contour line and are given in units of millibars. Generally, add a prefix of 9 to the value if the plotted pressure value is greater than 50 and a prefix of 10 if the plotted value is less than 50.


Surface Analysis

The surface front plot, colored in yellow, shows the current location of fronts using standard front symbology.