potential delay when using in-cockpit NEXRAD capabilities,  as the movement and/or intensification of weather could  adversely affect safety of flight.  square indicates the strongest display return within that 1.24  mile square area.  AIRMET/SIGMET information is available for the displayed  viewing range on the MFD. Some displays are capable of  displaying weather information for a 2,000 mile range.  AIRMETS/SIGMETS are displayed by dashed lines on the  map.  [Figure 13-19]  Although NEXRAD is a compilation of stations across  the country, there can be abnormalities associated with the  system. Some of the abnormalities are listed below.  The legend box denotes the various colors used to depict the  AIRMETs, such as icing, turbulence, IFR weather, mountain  obscuration, and surface winds.  [Figure 13-20]  The great  advantage of the graphically displayed AIRMET/SIGMET  boundary box is the pilot can see the extent of the area that  the advisory covers. The pilot does not need to manually plot  the points to determine the full extent of the coverage area.  METARs can be displayed on the MFD. Each reporting  station that has a METAR/TAF available is depicted by a flag  from the center of the airport symbol. Each flag is color coded  to depict the type of weather that is currently reported at that  station. A legend is available to assist users in determining  what each flag color represents.  [Figure 13-21]  The graphical METAR display shows all available reporting  stations within the set viewing range. By setting the range  knob up to a 2,000 mile range, pilots can pan around the  display map to check the current conditions of various  airports along the route of flight.  By understanding what each colored flag indicates, a pilot can  quickly determine where weather patterns display marginal  weather, IFR, or areas of VFR. These flags make it easy to  determine weather at a specific airport should the need arise  to divert from the intended airport of landing.  Pilots now have the capability of receiving continuously  updated weather across the entire country at any altitude.  No longer are pilots restricted by radio range or geographic  isolations, such as mountains or valleys.  In addition, pilots no longer have to request specific  information from weather briefing personnel directly. When  the weather becomes questionable, radio congestion often  increases, delaying the timely exchange of valuable inflight  weather updates for a pilot’s specific route of flight. Flight  Service Station (FSS) personnel can communicate with only  one pilot at a time, which leaves other pilots waiting and  flying in uncertain weather conditions. Data link weather  The resolution of the displayed data poses additional concerns  when the range is decreased. The minimum resolution for  NEXRAD returns is 1.24 miles. This means that when the  display range is zoomed in to approximately ten miles, the  individual square return boxes are more prevalent. Each  In addition, the base reflectivity is sampled at the minimum  antenna elevation angle. With this minimum angle, an  individual site cannot depict high altitude storms directly  over the station. This leaves an area of null coverage if an  adjacent site does not also cover the affected area.  The NEXRAD base reflectivity does not provide adequate  information from which to determine cloud layers or type  of precipitation with respect to hail versus rain. Therefore, a  pilot may mistake rain for hail.  In addition to the abnormalities listed, the NEXRAD system  does have some specific limitations.  Data Link Weather  Graphical METARs  NEXRAD Limitations  Base Reflectivity  Resolution Display  13-21  AIRMET/SIGMET Display  • Understand that the common perception of a “5-minute  latency” with radar data is not always correct.  • Get your preflight weather briefing! Having in-cockpit  weather capabilities does not circumvent the need for  a complete weather briefing before takeoff.  •  Use all appropriate sources of weather information to  make in-flight decisions.  •  Let your fellow pilots know about the limitations of  in-cockpit NEXRAD.  • Ground clutter  • Strobes and spurious radar data  • Sun strobes, when the radar antenna points directly at  the sun  • Interference from buildings or mountains that may  cause shadows  • Military aircraft that deploy metallic dust and may  reflect the radar signature  NEXRAD Abnormalities 