Which scenario would necessitate a SPECI for visibility?

• A. When prevailing visibility is below the aerodrome's highest alternate minimum visibility or 5000m, whichever is greater
• B. The runway lighting intensity changes
• C. Wind gusts exceed 30 knots
• D. Temperature changes by 5 degrees

Answer: (A)

A SPECI for visibility is issued when there is a significant change in visibility that could affect flight planning and operations. The specific threshold used is when the prevailing visibility falls below the aerodrome’s highest alternate minimum visibility, or 5,000 meters (whichever is greater). This matters because alternate planning relies on minimum visibility; if the actual visibility is worse than the most restrictive alternate minimum, crews may not be able to rely on diversions as planned, so a SPECI provides timely, critical information for decision-making. The other scenarios involve changes that do not directly cross this threshold for visibility reporting—runway lighting changes, strong wind gusts, or a temperature shift—so they don’t mandate a SPECI for visibility.