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Forecast Times

When a program involves viewing forecast information, the ability to determine the forecast time is necessary.  This value can also be set with the time resource.

Menu

This menu lists possible forecast times.  Since WXP does not make any assumptions as to what forecast times are available, this menu represents potential values of which some might not be valid for a particular model.

        Forecast Time Menu

  1: Initialized                     14: 4.5 day                       
  2: 6 hour                          15: 5 day                         
  3: 12 hour                         16: 5.5 day                       
  4: 18 hour                         17: 6 day                         
  5: 24 hour                         18: 6.5 day                       
  6: 30 hour                         19: 7 day                         
  7: 36 hour                         20: 7.5 day                       
  8: 42 hour                         21: 8 day                         
  9: 48 hour                         22: 8.5 day                       
 10: 60 hour                         23: 9 day                         
 11: 3 day                           24: 9.5 day                       
 12: 3.5 day                         25: 10 day                        
 13: 4 day                         
  0: Back to previous menu           -1: Exit program                  

Enter the time: 

The items in the time menu can be changed with the ".tim" menu files. This will allow you to set appropriate menu items based on model type.

Specifying Forecast Times

There are several ways to specify the forecast time in addition to above menu values. The syntax is:

time[-range][type]

You can specify a time by using entering the time and its units:

Value Description
init Initial time
anal analysis
12hr 12 hour forecast
h12 12 hour forecast
2day 2 day forecast
d2 2 day forecast
4.5day 4 1/2 day forecast
e4 4 1/2 day forecast
time use the value of the time resource (useful in var files)
miss missing value, take first available

The range is an hour range that is followed by the type of range.  The types of ranges are:

Value Description
rng range
avg average
acc accumulation
dif difference

This leads to several possible combinations:

Value Description
anal-12acc 12 hour accumulation up to analysis time or 12 hour observed accumulation.
anal-24dif 24 hour difference between current and previous 24 hours.
24hr-12acc 12 hour accumulation up to the 24 hour forecast time.
time-12acc 12 hour accumulation up to time specified in time resource (used in var files).

Forecast Times and GRIB Data

Often gridded model data is specified with a complex time.  The time and range syntax is a way of solving the problem of accessing these grids.  A simpler way is to specify only the valid time.

   -ft=24hr
   -ft=24hr-12acc

The GRIB search algorithm will find the first grid with that valid time.  The more verbose method will also work if there is more than one grid matching the same valid time.


For further information about WXP, email technical-support@weather.unisys.com
Last updated by Dan Vietor on June 1, 1998