What does "+RA" indicate in a METAR?

In METAR aviation weather reports, the symbol "+RA" is used to indicate heavy rain. This notation follows a standard format developed for reporting weather conditions at airports, ensuring that pilots and meteorologists can quickly understand current weather phenomena.

The prefix "+" signifies that the rain intensity is heavy, while "RA" is the specific meteorological code for rain. Meteorological reporting guidelines categorize precipitation intensity levels, distinguishing between light, moderate, and heavy rain. The use of "+" clearly communicates to aviators the significance of the weather conditions, which is crucial for flight planning and safety.

In this context, the other options do not accurately reflect the meaning of "+RA." Moderate rain would be indicated without the plus symbol, light rain would be designated as "RA" alone (without any prefix), and "No precipitation" would have a completely different coding. Therefore, recognizing that "+RA" specifically denotes heavy rain is essential for understanding METAR reports and assessing weather implications for aviation operations.