GAIRM

GAIRM makes provision to plot the G-AIRMET snapshots in 3-hour time bins.  While
snapshots are typically valid at a given forecast time, this option makes
provision to plot them continuously valid over a 3 hour time period from the
forecast time.  Included will also be any amendments or corrections.
Amendments and corrections are valid from the time they are issued until the
next 3-hourly valid forecast time.

The GAIRM parameter list follows similar conventions used for the AIRM function.
It includes the frame time for the airmet, the colors for the instrument
flight rules, mountain obscuration, turbulence, icing, sustained winds and
low-level wind shear, and flags for plotting symbols or airmet type, the end
time, and the flight levels on the map.  It also includes additional parameters
to render the plotting of G-AIRMETs at offset hours of -2, -1, 0, +1, and +2
hours.

Frame time|IR;MO;TB;IC;SW;WS clrs|TB color2|Flight Lvl|low;upper filter
lvl|Symbol flg|Time flg|Flight lvl flg| M2HROffset flg|M1HROffset flg|
0HROffset flg|1HROffset flg|2HROffset flg

Airmets that are valid at the frame time will be plotted on the map.  The frame
time is given as a GEMPAK date/time string.

The colors are separated by a semi-colon.  If any color is set to 0, that type
of symbol will not be plotted.  If any color is missing, a default will be used.
Defaults are red for instrument flight rules, yellow for mountain obscuration, 
light blue and magenta for turbulence, green for icing, dark pink for sustained
winds and cyan for low-level wind shear.

TB color2 is the second color for turbulence. The color from the first list will
be used to plot Turbulence AIRMETs below the specified level. The color listed
as the second color will be for Turbulence AIRMETs above the specified level.

Flight lvl is the dividing level for the turbulence display. The value is in
hundreds of feet.

The lower and upper filter levels are flight level values used to filter the
GAIRM data display. If neither value is given, then all data is plotted. If only
the lower level is present, then only data above that level is displayed. For
the upper level only, data below this upper value are displayed. If both values
are given, then the data is plotted for levels between the two boundary values.

The symbol flag is YES or NO and controls whether or not to plot a symbol or
identifying text for the airmet on the map.  The default is NO.

The time flag is YES or NO and controls whether or not to plot the start time of
the airmet on the map.  The default is NO.

The flight level flag is YES or NO and controls whether or not to plot the
flight level(s) in hundreds of feet on the map.  The default is NO.

The flags named M2HROffset (for minus 2 hour offset), M1HROffset, 0HROffset,
1HROffset (for plus 1 hour offset), and 2HROffset  are used to indicate how the
G-AIRMET snapshots are plotted with respect to the underlying frame time
associated with an image.  If omitted, the default is to use a 0 Hour Offset
where snapshot times are time matched to the satellite imagery, but plotted over
3 hour time bins.  A combination set of snapshot images over transition times
can be rendered if multiple flags are selected.

An example string to render the G-AIRMETs, for IFR & MT_OBSC hazards in colors
of red and yellow, with a 0 hour offset:

    GAIRM = ${yymmdd}/${hhmm}|2;20;0;0;0;0|||Y|Y|Y|N|N|Y|N|N

An example string to render the G-AIRMETs for all hazards with a 0 hour offset.
Turbulence AOA 180 kft is rendered in color 10:

    GAIRM = ${yymmdd}/${hhmm}|1;2;3;4;5;6|10|180|Y|Y|Y|N|N|Y|N|N

An example string to render the G-AIRMETs for all hazards with a -1, and -2 hour
offset.  Turbulence AOA 180 kft is rendered in color 10:


GAIRM = ${yymmdd}/${hhmm}|1;2;3;4;5;6|10|180|Y|Y|Y|Y|Y|N|N|N