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Forecast Center

The United States does not lie in the tropical latitudes, but American forecasters must nevertheless be well-versed in tropical weather phenomena. Most of the time this type of weather comes in the form of subtropical highs, which bring dull, hot conditions.  There are also easterly waves that often rake the Gulf Coast region with showers and thunderstorms. This issue, however, introduces a tropical cyclone and illustrates its effect on meteorological charts.

This weather map is for an event during the afternoon hours in September. 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 example, 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.

For additional information, along with helpful hints and advice, visit

The solution appears on page 66.

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