Two other, much smaller files can also be regarded as 'customized'. The file custinit.txt contains information for program boot-up, including the default site along with many parameters that preserve various settings you choose when you run the program. The file retini.txt contains similar information for use with the data retrieval module.
Some description of the customization process is in order, partly so that if you choose to order, you know what kind of work you're paying for. The data types in cty.fdt file entries can be grouped roughly into the following categories:
As you might surmise, the customization process in quite involved. The various parameters interact in many subtle ways in the program, so considerable care is necessary. Over the years, I've developed a number of tools which help greatly. Some of these I use every time, and some only for certain types of sites. I have a program which helps me set up most of the data, but I always go back and make adjustments after the intital creation. I regularly use a program which maps out the parameters for previous sites I've done, so that I can build on that experience in an organized way. For many major U.S. sites, I have a vast amount of data from the National Climatic Data Center, and a program I wrote for powerful analysis of that data, including graphs of 'model days', consisting of dozens of days meeting selected criteria. I can then directly, graphically compare WXSIM output to this actual data and tweak cty.fdt to improve the fit. I have written other software which helps me do something similar with home weather station data (especially Davis stations). My climatological data sources include various internet sites and Tim Vasquez's Digital Atmosphere. Finally, I almost always run test forecasts using real-time data, and either wait a day or two to see how they verify, or compare to other forecasts for the area.
In the past, the above work tooke me anywhere from 2 or 3 hours in the case of very straightforward sites in locations where I have a lot of prior experience, up to 12 or more solid hours of work for especially challenging cases, such as a mountain near a coast, with years of home weather station data to analyze. On average, a customization took me perhaps 5 or 6 hours, spread out over two or three days.
I have found ways to slightly reduce the time spent customizing, but have also added new tasks, such as routinely analyzing users' home weather station data and repeatedly testing against climatology and also output from surrounding, previously done sites. This has kept customization time generally about 3-4 hours. However, there are now two options: basic customization, which includes the above bulleted points and takes about 2 hours or a bit more, and enhanced, in which I still (for a bit more pay) do the full-blown job, taking perhaps 4 hours. The accuracy difference should be small in most cases, so the basic option is fine for most customers. For some sites, though, the extra cost and effort may be worthwhile and yield a noticeable improvement in temperature forecasts. Click here for more details.
This work is the main thing you're paying for with customization. I could probably do it quicker, but I'm frankly rather obsessed about getting it right - or at least as good as possible - and that's good for you!
Customizing the companion program WXSIMATE takes much less time, once I've done all the work setting up WXSIM itself. I develop a registration code which enables WXSIMATE to use WXSIM's custom files, and - especially if you are ordering the WXSIM/WXSIMATE bundle - also leave various settings in a state appropriate to your region.