forti-prep

Converts NetCDF forecast files into the binary format expected by the forti system, and writes the result to a local directory.

Usage

forti-prep --config <config.json> --output-dir <output> --version <n> <nc-file>

Option	Default	Description
--config	config.json	JSON config file describing parameters to extract
--output-dir	data	Directory to write output files into
--version	0	Version number to attach to the output

See sample_config.json for a config example.

Config format

{
  "area": "arctic",
  "dimensions": {
    "x": "x",
    "y": "y"
  },
  "parameters": {
    "wind_speed_10m": {
      "conversion_method": "vector_to_speed",
      "variables": {
        "x": { "netcdf_name": "x_wind_10m", "units": "m/s" },
        "y": { "netcdf_name": "y_wind_10m", "units": "m/s" }
      }
    }
  }
}

The top-level fields are:

Field	Description
area	Identifier for the geographic area (e.g. "arctic", "meps")
dimensions	Names of the x and y spatial dimensions in the NetCDF file
parameters	Map of output parameter names to their extraction configuration

Each parameter entry has a conversion_method and a variables map. Each variable entry requires netcdf_name (the variable name in the NetCDF file) and units (the desired output unit). If the unit in the NetCDF file differs, it is automatically converted using cf-units.

Supported conversion_method values and their required variable keys:

Value	Required variable keys	Description
null	(parameter name)	No conversion; reads the variable whose key matches the parameter name directly
vector_to_speed	x, y	Wind speed from x/y vector components
vector_to_direction_from	x, y	Direction the wind is coming from (meteorological convention)
vector_to_direction_to	x, y	Direction the wind is blowing towards
precipitation_amount_1h	total_precipitation	1-hour precipitation from accumulated values
precipitation_amount_6h	total_precipitation	6-hour precipitation from accumulated values
weather_symbol_1h	total_precipitation, total_cloud_cover	1-hour weather symbol from accumulated precipitation and cloud cover
weather_symbol_6h	total_precipitation, total_cloud_cover	6-hour weather symbol from accumulated precipitation and cloud cover
weather_symbol_12h	total_precipitation, total_cloud_cover	12-hour weather symbol from accumulated precipitation and cloud cover

Setup

Requires Python 3.13+. Dependencies are managed with uv:

uv sync