What does the word "AUTO" in a METAR message indicate?

• The presence of "AUTO" in a METAR report message indicates a fully automated report with no human intervention.

• Absence of AUTO indicates that the report is either a manual report or an automated report with an observer logged on to the system.
  (The report modifier group which contains the AUTO or COR modifiers does not appear in all reports.)

What does the word "COR" in a METAR message indicate?

• Presence of "COR" in a METAR means that a corrected METAR or SPECI is being transmitted. "COR" report invalidates a previous message and replaces it with a "COR" message.

Can "AUTO" and "COR" be in a METAR message simultaneously?

• "AUTO" and "COR" cannot be transmitted in the same METAR. Logic indicates that if the term "COR" is used, the observation cannot be "AUTO", because someone (observer) is correcting it.

• Any automatic "AUTO" report generating system has no way of knowing that the previous message needs to be corrected since it was generated by the rules programmed into the system.

• If an observer is not monitoring METAR observations from a weather station, than by default, the METAR report messages sent from the weather station must contain the modifier word "AUTO".

• "AUTO" informs the pilot that the system is not being monitored by a human observer and the associated risks.

When is SPECI report generated and what is it?

• SPECI is issued and transmitted when a significant change in weather conditions occurs (deterioration or improvement). Significant change in winds and gusts, visibility, cloud base height or occurrence of severe weather. It can be issued by an AUTO METAR generating system based on ICAO & WMO guidelines.

Paraphrased from: Aeronautical Information Manual Study Guide For The Private Pilot: 2013

For more information about the MeteoHelix®, ezMETAR airport weather stations and AUTO-METAR weather monitoring system please visit BARANI DESIGN website: www.baranidesign.com or visit us in person at Farnborough Airshow 2018 in hall 3, booth 3418. 

Basic AUTO-METAR example:

• LZPH12345 112000Z AUTO 00000KT //// // ////// 26/16 Q1007

METARlogGSM sends a METAR report in the following format to any specified FTP server & port: 
METAR LZPH12345 112000Z AUTO 29006KT //// // ////// 26/16 Q1007=

Complex AUTO-METAR example:

• EGLL 081420Z AUTO 29006KT 260V340 9999 VCTS SCT038/// //////CB 25/15 Q1023 TEMPO 4000 +TSRA