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November-December 2017

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Forecast Center

With the arrival of late summer and fall our attention turns south to the Gulf coast, where powerful tropical cyclones frequently affect the subtropics. We'll take a look at analyzing such an event from this year.

This weather map depicts conditions in September during the late morning hours. Draw isobars every four millibars (996, 1000, 1004 millibars, 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 millibars when the number shown is below 500, and 9xx.x when it is more than 500. For instance, 027 represents 1002.7 millibars and 892 represents 989.2 millibars. Therefore, when one station reports 074 and a nearby one shows 086, the 1008 millibar isobar will be found halfway between the stations. Then try to find the locations of fronts, highs, and lows.

For a detailed, printable version of this map, along with helpful hints and advice, visit


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

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