Which METAR elements are typically not reported when missing?

In METAR reports, certain elements can vary in terms of their frequency of reporting. When the report contains missing data, specific elements are typically not included in the report.

The correct answer focuses on report modifiers, present weather groups, and remarks. These elements are considered additional information and are often not mandatory. When conditions do not warrant their inclusion, or if the data is unavailable, they can be omitted without affecting the fundamental meteorological information provided by the METAR.

For example, report modifiers (like the type of observation) may not always apply depending on the location or time of year, while present weather groups (which describe phenomena such as rain or snow) might only be included if conditions are sufficiently significant to warrant mentioning them. Similarly, remarks are supplementary notes that can be included only if pertinent but are not essential for basic weather reporting.

The other options contain elements that are typically required for a comprehensive METAR report. Elements like visibility, cloud cover, and altimeter settings are crucial for operational aviation purposes and are generally included unless there is an exceptional reason to omit them. Likewise, wind direction and speed, temperature, and humidity are often considered standard metrics for a METAR and are usually reported as part of the basic data required for air traffic