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Coordinated Universal Time
scaffolding activity

Weather data is reported in Coordinated Universal Time (UTC) and this system is based upon a 24-hour clock of time measured along the Prime Meridian (0 degrees longitude) in Greenwich, England. Since most people are more familiar with the AM/PM time system, it is important to be able to convert from UTC to AM/PM when determining the local time for which a weather map is valid. The purpose of this activity is to introduce Coordinated Universal Time, and how to convert between local time and UTC. Key words throughout this activity link directly to helper resources that provide useful information for answering the questions.

Converting From UTC to Local Date and Time:

The Coordinated Universal Time (UTC) for each image is typically given in the upper right hand corner, as was the case for the map of surface observations given above. Use the time on this weather image to convert from UTC to local AM/PM data and time for each of the following cities. For example, the time of this example image is 2000Z 28 October 1996 in UTC and converting that to Central Standard Time (CST) yields October 28, 1996, 2:00 PM (CST). The cities below are located in different time zones, and this will affect the result of the conversion.

1) Convert from 2000Z 28 October 1996 UTC to Central Standard Time (CST) for Chicago, Illinois.

2) Convert from 2000Z 28 October 1996 UTC to Eastern Standard Time (EST) for New York City, New York.

3) Convert from 2000Z 28 October 1996 UTC to Pacific Standard Time (PST) for San Francisco, California.

4) Convert from 2000Z 28 October 1996 UTC to Mountain Standard Time (MST) for Denver, Colorado.

More Difficult Conversions:

As was done for the previous section, convert the UTC time on the map above to local times for the following cities.

5) Convert from 0500Z 29 October 1996 UTC to Central Daylights Savings Time (CDT) for Chicago, Illinois.

6) Convert from 0500Z 29 October 1996 UTC to Eastern Daylight Savings Time (EDT) for Nashville, Tennessee.

7) Convert from 0500Z 29 October 1996 UTC to Pacific Daylight Savings Time (PDT) for Boise, Idaho.

8) Convert from 0500Z 29 October 1996 UTC to Eastern Standard Time (EST) for Miami, Florida.

Reporting Current Local Time:
9) Now apply your UTC conversion skills to current weather images. Go to the Weather Visualizer ( CoVis version | public version) and create the latest map of surface observations. From this image, convert the UTC time (on the image) to your local AM/PM time and be sure to show your calculations.

If the Weather Visualizer is too busy, here are additional web sites for accessing current weather data.

midlatitude cyclones
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

observation symbols