What must pilots determine when observing current weather from a METAR?

When pilots observe current weather from a METAR, one of the critical factors they need to ascertain is the need for an alternate airport. METAR reports provide essential information about the weather conditions at an airport, including visibility, wind direction and speed, cloud cover, and significant weather phenomena. This information is crucial for pilots in deciding whether they can safely land at the intended destination or if they need to divert to an alternate airport.

The determination of needing an alternate airport is based on regulations and guidelines that state if the weather conditions at the destination are below certain visibility or cloud cover criteria, an alternate must be available for safety purposes. Thus, interpreting METAR data helps pilots ensure that they can reach their destination safely and have a backup plan in the case that the weather conditions turn unfavorable.

In contrast, while route planning, runway surfaces, and fuel requirements are important considerations for flight operations, they are derived from a broader context that includes various factors beyond just the current weather information found in METAR reports.