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January-February 2009

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Forecast Center

All eyes are on the seas when it comes to winter weather. The world’s oceans, containing 300 million cubic miles of water, make up a massive storehouse of thermal energy. Even though landmasses cool rapidly, snow cover expands, and the polar icepack develops, the oceans feed enormous amounts of warmth back into the atmosphere on the open seas. This often destabilizes the atmosphere and produces clouds, fronts, and powerful weather systems. These seasonal characteristics were known even to the ancient Romans, who feared crossing the Mediterranean during the cool season.

This weather map is for an event during an afternoon in late November. 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 further information, along with helpful hints and advice, visit

The solution appears on page 66.

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