The -ftime option nominally prints the Forecast time stamp
such as the forecast hour, accumulation period, etc.
Types of time stamps
There are two types of simple time stamps, simple ones like a
The next step up is a single statistical processing which involves a statistical operator
(such as average, accumulation, maximum) and one or more fields. Examples are
- analysis, anl
- 12 hour forecast, 12 hr fcst
- average (00Z analysis, 06Z analysis, 12Z analysis, 18Z analysis), 4@6 hr ave(anl)
- average (analysis, 6 hr fcst, 12 hr fcst, 18 hr fcst), 0-18 hr ave(fcst,dt=6 hr)
- average (every forecast time step from 6 to 12 hours), 6-12 hour ave fcst
The next step is where you have multiple statistical processing steps. For example, you have
the precipitation over 6 hour which involves a single statistical processing step. Now you take the monthly
mean of that. That involves two statistical processing steps. Now if you take make a 30-year
climatology, then you need 3 statistical processing steps.
It was noted that the old ftime had problems with the more complicated time stamps and
ftime2 was developed to be an eventual replacement. Currently (9/2017), you can use the
old ftime by -ftime1 and the new ftime by -ftime2 .
For the time being, -ftime will use -ftime1; however,
that will change to -ftime2 in the future.
Similarily set_ftime2 was developed
to replace the old set_ftime/set_ave options.
$ wgrib2 grib2.polar -ftime
1.1:0:24 hour fcst
1.2:0:24 hour fcst