Aviation Weather Services

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