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Everything You Need to Know about AWOS and ASOS

Relevant Discussion: AIM 4-3-26, 7-1-1, 7-1-11, 7-1-17, 7-1-29, 7-1-30, FAA-H-8083-16, 8083-25, AC 150/5220-16, order 8260.19F 8-6-6 Nathan Rambo
Gemini Sparkle

Key Takeaways:

  • AWOS (Automated Weather Observing System) provides minute-by-minute weather updates with various levels of detail (AWOS-A to AWOS-4), while ASOS (Automated Surface Observation System) offers more sophisticated hourly observations designed for METARs and TAFs.
  • AWOS levels vary from basic altimeter settings to comprehensive data including wind, temperature, visibility, and cloud/ceiling, whereas ASOS adds capabilities like precipitation type/intensity, wind shifts, and specialized cloud/visibility averaging.
  • Both AWOS and ASOS information is accessible in flight and by telephone, but they have reporting limitations, such as an upper limit of 12,000 feet for cloud height and 10 miles for visibility.
  • Pilots must legally adhere to official AWOS/ASOS reports for VFR flight minimums (e.g., §91.155), as personal visual assessments cannot supersede these automated observations.
See a mistake? Contact us.

AWOS: Automated weather observing system. A suite of weather sensors of many different configurations either procured by the FAA or purchased by individuals, groups or airports that are required to meet FAA standards. AWSS — automatic weather sensor system — is functionally the same as ASOS.

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