What type of observation is required when a wind shift occurs?

The correct answer is "SPECI." In aviation weather reporting, a SPECI is a type of observation that is generated when significant changes occur in weather conditions, and a wind shift is specifically one of those significant changes that necessitate an updated report.

SPECI reports are typically issued when there is a change in wind speed of 10 knots or more, a wind shift of 30 degrees or more, or when significant changes in visibility, temperature, or other critical weather variables occur. These observations are particularly important as they provide timely updates to pilots and other aviation stakeholders, ensuring that safety and operational efficiency are maintained.

The other options available do not specifically denote the reporting of significant weather changes like a wind shift. For example, a SPECIAL observation might refer to irregular weather observations during specific situations, but it does not explicitly identify the criteria for changes like wind shifts. Similarly, an UPDATE typically refers to minor amendments to existing reports rather than new significant observations, and AIR REPORT usually pertains to reports made by pilots in flight relating to weather conditions but does not focus on the criteria for wind shifts.

SPECI serves as a critical means for communicating immediate and relevant weather changes necessary for safe aviation operations.