The National Transportation Safety Board (NTSB) yesterday issued a Safety Alert to warn pilots using in-cockpit FIS-B and Satellite Weather display systems that the NEXRAD "age indicator" can be misleading. The actual NEXRAD data can be as much as 20 minutes older than the age indication on the display in the cockpit. If misinterpreted, this difference in time can present potentially serious safety hazards to aircraft operating in the vicinity of fast-moving and quickly developing weather systems.
NEXRAD mosaic imagery depicts weather conditions from multiple ground radar sites. The NEXRAD "age-indicator" on the cockpit display indicates the time that the mosaic image was created, not the time of the actual weather conditions. The NEXRAD image is always older than the actual weather conditions.
The NTSB has cited two fatal weather-related aircraft accidents in which NEXRAD images were displayed to the pilot that were presented as one-minute old on the age-indicator, but contained information that was up to five to eight minutes behind the real-time conditions.
In addition to raising pilot awareness on this issue, the Safety Alert also reminds pilots of the importance of obtaining a thorough preflight weather briefing.
The Safety Alert is available at http://go.usa.gov/v0Z.