Who will re-evaluate surface prevailing visibility upon initial receipt of a differing control tower value and upon subsequent reportable changes at the control tower level?

• A. Weather technicians at augmented EUs
• B. ATC directives
• C. Observing Aids for Visibility
• D. METAR technicians

Answer: (A)

When the control tower reports a visibility value that differs from what is currently prevailing, the task of confirming and updating the field visibility falls to the weather technicians assigned to augmented weather units. They actively re-evaluate surface prevailing visibility at the moment a new tower value is received and again whenever there are later reportable changes at the tower level. This ensures that the visibility used for METARs and flight operations truly reflects conditions on the airfield, drawing on all available data sources and observations to make the correct adjustment.

ATC directives don’t perform this recalculation, and the observing aids for visibility are the instruments that gather data rather than re-interpret it. METAR technicians are concerned with producing the METAR reports, but the re-evaluation trigger and authority in this scenario rest with the weather technicians at augmented weather units.