TM 1-1510-218-10 3–81 (2)   Main   Menu.    The  main  menu  provides access to the two weather mode views and additional system     functions,     including     checklists,     time/date information,  options,  and  navaid  display.    To  select  a specific menu item, press  NEXT button on the display until the desired item is highlighted and press the  GO button to view the selected menu item. (3)   Weather   Modes.      Two   weather   mode views  are  available  from  the  main  menu  by  pressing either the 360° or the 120° button.  Refer to Figures 3- 113 and 3-114, respectively.  The symbol Ü means to "go to."  When the weather mode is initially selected, it will  always  be  in  the  200  nm  range.    Pressing  the button  beside  the  range  setting  will  cycle  through  the additional range selections from 200 nm  to 100 nm to 50  nm  to  25  nm  and  back  to  200  nm.    The  25  nm range  is  indicated  by  a  solid  ring  to  advise  of  close proximity  to  potential  thunderstorms.   Either  view  can be selected from the main menu or the opposite view.   When  changing  from  one  view  to  another,  the  range remains constant. BFG BRT OFF 25 MENU CLEAR 200 nm 120 ⁰ Figure 3-113.  360º Weather Mode BFG BRT OFF MENU 360 ⁰ 25 CLEAR 200 nm 022 ⁰ Figure 3-114.  120° Weather Mode Press the   CLEAR  button  to  erase  all  weather data   from   the   display   and   system   memory.      The intensity  of  a  thunderstorm  can  be  identified  by  the speed  with  which  the  discharge  points  appear.    The system    continually    receives    and    processes    new electrical    discharge    information.        Monitor    this    by pressing the clear button often.  The more intense the storm, the faster the discharge points reappear. Multiple   discharges,   which   appear   as   clusters, are indicative of thunderstorm activity.  A large number of discharge points indicate a faster rate of occurrence and,  therefore,  a  more  severe  thunderstorm.    Fewer discharge points indicate a smaller, but not necessarily weaker, cell.  Thunderstorm conditions change rapidly and  monitoring  their  activity  over  a  period  of  time  by use  of  the    CLEAR  function  is  recommended.    Any grouping of discharge points within the 25-nm range is cause for immediate avoidance. The  Stormscope  system  should  never  be use d to attempt thunderstorm penetration.   The FAA and AIM recommend avoiding, by at least 20 miles, any thunderstorm identified  as  severe  or  giving  an  intense radar echo. WARNING