Which of the following situations would meet the SPECI criteria?

The situation that would meet the SPECI criteria is when a tornado is observed. SPECI reports are used to issue significant weather changes between routine METAR observations for aviation purposes. This system allows for the timely communication of weather phenomena that can impact flight safety and operations.

When a tornado occurs, it is considered a significant weather event that dramatically affects visibility, wind dynamics, and overall safety in the vicinity. The presence of a tornado warrants immediate reporting, adhering to the urgent need for situational awareness in aviation and meteorological contexts.

In contrast, a wind speed of 10 knots does not represent a significant change or hazard, thus not qualifying for a SPECI report. An increase in temperature by itself is also not considered significant unless it exceeds certain thresholds, which are typically predefined criteria. Furthermore, the occurrence of no significant weather does not trigger the need for a SPECI report, as it indicates that conditions remain stable and predictable.