What is the primary purpose of a METAR report?

A METAR report is primarily designed to provide timely and accurate weather observations at a specific location, typically an airport, which are crucial for aviation operations. These reports include essential information such as temperature, dew point, wind speed and direction, visibility, clouds, and current weather phenomena.

While option C discusses watching for trends in weather, it's important to clarify that METAR reports are not inherently designed for detecting long-term trends. Instead, they serve as a snapshot of current weather conditions, which can be used to inform immediate decisions rather than identify prolonged weather patterns or trends over time. This makes METAR reports particularly valuable for pilots and air traffic control, as they need real-time data for safe flight operations.

Other options, including tracking long-term weather patterns, observing daily temperatures, and determining air quality levels, do not align closely with the function of METAR reports. They focus on specific tasks or measurements that extend beyond the immediate and concise nature of these weather updates, which are specifically tailored for short-term aviation and operational use.