Garmin G1000H Bell 407GX Pilot's Guide - Page 303

HAZARD AVOIDANCE Displaying NEXRAD weather information: 1) Select the MAP Softkey (for the PFD Inset Map, select the INSET Softkey). This step is not necessary on the Weather Data Link (XM) Page. 2) Select the NEXRAD Softkey. Composite data from all the NEXRAD radar sites in the United States is shown. This data is composed of the maximum reflectivity from the individual radar sweeps. The display of the information is color-coded to indicate the weather severity level. All weather product legends can be viewed on the Weather Data Link (XM) Page. For the NEXRAD legend (Figure 6-11), select the LEGEND Softkey when NEXRAD is selected for display. No Radar Coverage Figure 6-11 NEXRAD Data with Legend The display of radar coverage is always active when either NEXRAD or ECHO TOPS is selected. Areas where NEXRAD radar coverage and Echo Tops information is not currently available or is not being collected are indicated in gray shade of purple. Reflectivity Reflectivity is the amount of transmitted power returned to the radar receiver. Colors on the NEXRAD display are directly correlative to the level of detected reflectivity. Reflectivity as it relates to hazardous weather can be very complex. The role of radar is essentially to detect moisture in the atmosphere. Simply put, certain types of weather reflect radar better than others. The intensity of a radar reflection is not necessarily an indication of the weather hazard level. For instance, wet hail returns a strong radar reflection, while dry hail does not. Both wet and dry hail can be extremely hazardous. The different NEXRAD echo intensities are measured in decibels (dB) relative to reflectivity (Z). NEXRAD measures the radar reflectivity ratio, or the energy reflected back to the radar receiver (designated by the letter Z). The value of Z increases as the returned signal strength increases. 190-01255-00 Rev. A Garmin G1000H™ Pilot's Guide for the Bell 407GX 291