Garmin GXM 51 GXM 51 Installation Instructions - Page 7

Weather and Sea Surface Information The GXM 51 receives XM Weather Radio data and shows it on your chartplotter. The weather data for each feature comes from reputable weather data centers such as the National Weather Service and the Hydrometerological Prediction Center. (See the XM WX Satellite Weather Web site at http://weather.xmradio.com/weather for more information.) Any weather feature can change in appearance or interpretation if the source that provides the information changes. XM Weather Radio data is broadcast at set rates. For example, NEXRAD Radar data is broadcast at five minute intervals. When the marine network is turned on or when a new feature is selected, the GXM 51 has to receive new data before it can be displayed. For this reason you may experience a delay before weather data or a new feature appears on the map. WARNING: The XM Weather Radio data is merely supplemental and advisory in nature and is not intended to be relied up on as safety-critical information. You should always exercise caution and common sense when confronted with severe weather conditions. WARNING: XM WX Weather should not be used for hazardous weather penetration. Weather information is approved only for weather avoidance, not penetration. Weather-Related Broadcast Rates Feature NEXRAD Cloud Tops Storm Cells Lightning Wind Pressure Hurricanes Visibility Fronts Sea-Surface Temperature Wave Height Wave Period Wave Direction Current Conditions Forecasts Sea-Surface Conditions Broadcast Rate (minutes) 5 15 1.25 5 12 12 12 12 12 12 12 12 12 12 12 12 NEXRAD Overview NEXRAD Description NEXRAD Radar is a Doppler radar system that has greatly improved the detection of meteorological events such as thunderstorms, tornadoes, and hurricanes. An extensive network of NEXRAD stations provides almost complete radar coverage of the continental United States, Alaska, and Hawaii, and the majority of Canada. The range of each NEXRAD is 124 nautical miles. NEXRAD Abnormalities There are possible abnormalities regarding displayed NEXRAD images. Some, but not all, of those include the following circumstances: Ground clutter Strobes and spurious radar data Sun strobes, when the radar antenna points directly at the sun Military aircraft deployment of metallic dust (chaff), which can cause alterations in radar scans Interference from buildings or mountains, which may cause shadows NEXRAD Limitations Certain limitations exist regarding the NEXRAD radar displays. Some, but not all, are listed here for your awareness: NEXRAD base reflectivity does not provide sufficient information to determine cloud layers or precipitation characteristics (for example, determining between hail and rain). GXM 51 Installation Instructions