As this issue hits newsstands and mailboxes, winter 2015–2016 is blowing in across much of the United States, bringing the majority of weather systems from the West Coast and Canada. Furthermore, this winter is expected to be an active El Niño year, which favors a higher frequency of storm tracks driving onshore onto the West Coast. In this issue we'll take a look at how to analyze a classic example of such a system and understand how it works.
This weather map depicts conditions in November during the midday hours. Draw isobars every four millibars (996, 1000, 1004 mb, etc.) using the plot model example at the lower right as a guide. As the plot model indicates, the actual millibar value for plotted pressure (xxx) is 10xx.x mb when the number shown is below 500, and 9xx.x when it is more than 500. For instance, 027 represents 1002.7 mb and 892 represents 989.2 mb. Therefore, when one station reports 074 and a nearby one shows 086, the 1008 mb isobar will be found halfway between the stations. Then try to find the locations of fronts, highs, and lows.
TIM VASQUEZ is a former Air Force forecaster and author of Digital Atmosphere, a weather forecasting software program. He lives near Norman, Oklahoma, where he keeps busy as a weather consultant and software developer.