When is a SPECI issued?

A SPECI, or significant meteorological report, is issued when there is a significant change in environmental conditions that are impactful enough to warrant an update to the prevailing weather information. These changes can include alterations in visibility, wind, weather phenomena, or significant variations in atmospheric pressure. SPECI reports ensure that pilots, ground personnel, and aviation enthusiasts have the most current information which is critical for safe operations, particularly in rapidly changing weather scenarios. Such reporting helps in maintaining a high level of safety and preparedness in aviation.

The other options do not accurately describe the circumstances surrounding a SPECI issuance. Regular intervals typically characterize routine METAR updates, while meteorological equipment failures may lead to different types of notices or alerts, not specifically a SPECI. Moreover, the issuance does not pertain to stable conditions; rather, it responds explicitly to significant changes in weather that require immediate communication.