NOTE: This Concept for the Day is a repeat of that which appeared in the previous week's Tuesday Weather Summary.
You will find that all DataStreme meteorological maps and charts are labeled with numbers followed with a "Z", such as 00Z, 12Z, 1915Z, etc. These labels indicate the time of observation in Universal Coordinated Time (UTC). The UTC or "Z" time is used because weather observations must be taken at the same time everywhere to accurately represent the state of the atmosphere. But how can you tell from the reported Z time when the observations were made where you live?
Z time is the time along the Prime Meridian, 0 (zero) degrees longitude. Life would be easy if you lived in England because your local time and Z time are the same. But what about where you live? For example, if you are looking at today's 12Z weather map, what time was it in your time zone?
Because you live in the U.S. and the earth rotates toward the east, your local time will be earlier than the local time at the Prime Meridian -- that is, the sun rises in England hours before it does in the U.S. Presently, many of us observe Daylight Saving Time. Therefore, 12Z (noon in England) would be 8 AM Eastern (4 hours earlier than local time in England), 7 AM Central (5 hours earlier), 6 AM Mountain (6 hours earlier), and 5 AM Pacific time (7 hours earlier). However, UTC time does not change seasonally. So when the entire country reverts to Standard Time at the end of October for the winter season and we set our own clocks back one hour, 12Z would then become 7 AM Eastern (5 hours earlier than local time in England) .
A table of time conversions for the U.S. is listed on page 26 in the DataStreme Homepage User's Guide. For additional Z-time explanation, call up Tuesday's optional Supplemental Summary Information.
To be submitted on the lines for Tuesday on the Study Guide, Part B, Applications', Chapter 1 Progress Response Form, under section B. Daily Summary (found in Week 1 section of Part B and also on DataStreme Homepage).