Explanation of Hourly Surface Weather Observations

(In Tabular Form)

The table of weather observations for the selected weather station represents the hourly observations (in a format that is not coded) for the previous 24 hour interval. All times, to include the "Starting" and "Ending" times, are listed in UTC or Z time . These files are updated on an hourly basis. The tabular entries include:

• TIME = Hourly observation time in "Z" time.
• T = Air temperature in degrees Fahrenheit
• TD = Dewpoint temperature in degrees Fahrenheit
• DIR = Wind direction in degrees measured clockwise from true north (360 degrees)
  • (090 = east wind, 180 = south wind, 270 = west wind and 00 = calm)
• SPD = Wind speed in knots
• GST = Speed of the wind gust in knots
• ALT = Altimeter setting in inches of mercury
  • (the lead 2 or 3 is omitted)
• SLP = Sea level corrected pressure in millibars
• VIS = Horizontal visibility in statute miles
• CEIL = Height of ceiling in hundreds of feet.
• COV = Sky or Cloud Cover
  • Listed either in ocktas or eights of sky cover - such as 2/8, etc. or
  • CLR = clear, SCT = scattered; BKN = broken; OVC = overcast.
• WX = Significant Weather Phenomena
• EXT = Maximum or minimum daily temperature (maximum at 0600 Z)
• PR6 = Precipitation for the previous 6 hours (at 0000, 0600, 1800 Z).
• PR24 = Precipitation for the previous 24 hours (at 1200 Z)
• SC

Last revision 23 June 1996

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