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Missouri Department of Transportation

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AWOS Data Explanations


Current METAR for all Airports
Glossary - Disclaimer

  • Air Temperature is measured in degrees Celsius by a sensor located six feet off the ground. The display is also in degrees Fahrenheit.
  • Dew Point temperature is the temperature, measured in degrees Celsius, at which the air is fully saturated with moisture. The display is also in degrees Fahrenheit. The dew point is a more useful measure of the moisture present, because it takes into consideration the air temperature. The amount of moisture air can hold decreases when it is cooled. As the air temperature drops there is a point at which the moisture in the air begins to condense and form fog, dew or frost. The point is the dew point.
  • Barometric Pressure is the amount of downward force exerted by the weight of the air above and is measured in inches of mercury (Hg).
  • Wind Speed is the average velocity at which the air travels over a one-minute period and is measured in nautical miles per hour (NM/H or knots). The display is in miles per hour (mph), with the knots in parentheses.
  • Peak Wind Gusts are the highest wind speeds registered over the previous 10 minutes, measured in nautical miles per hour (NM/H or knots). If no gusts are detected more than 5 NM/H faster than the average wind speed, this field is zero. The display is in miles per hour (mph), with the knots in parentheses.
  • Wind Direction is the average direction from which the wind is coming and is measured in degrees from north. The display is given as an alphabetic code denoting the direction, with degrees from north in parentheses.
  • Visibility is the distance a person can see with normal vision, and is measured in statute miles.
  • 1st Cloud Layer is the height, in feet, above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken", "overcast", or "obscuration", and not classified as "thin" or "partial".
  • 2nd Cloud Layer is the 2nd layer of clouds above the earth's surface.
  • 3rd Cloud Layer is the 3rd layer of clouds above the earth's surface.
  • Density Altitude is the altitude in the International Standard Atmosphere that has the same air density as the air being evaluated. The altitude is displayed in feet, when 1000 feet is greater than the field elevation, and is computed from the temperature, dew point, altitude and barometric pressure.
  • Variable Wind Directions are the span of direction from which the wind is coming. The directions are given as the span of degrees from true north.
  • Variable Visibility is the lowest and highest value of prevailing visibility during a given observation period. If the prevailing visibility rapidly increases and decreases by 1/2 statute mile or more during the time of the observation, and the prevailing visibility is less than 3 miles, the visibility is considered to be variable.
  • Day/Night is the determination of whether it is day or night on the ground at the airport. This determination is made by an ambient light sensor.
  • Thunderstorm and Precipitation Identification identifies if there is a thunderstorm within the vicinity of the airport and the type of precipitation.
  • Thunderstorm Remarks includes other pertinent information about the storm, including the presence and direction of lightning.




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