Cause of the error:

This is known issue when downloading data in the NetCDF format:

For example, you select all times (00:00, 06:00, 12:00, 18:00) and you select all steps (0 to 120 in 3-hour steps).

In this case you will get data for:

2016-12-01, 00:00 (time 00:00 + step 0)

2016-12-01, 03:00 (time 00:00 + step 3)

2016-12-01, 06:00 (time 00:00 + step 6)

2016-12-01, 06:00 (time 06:00 + step 0)

2016-12-01, 09:00 (time 06:00 + step 3)

... and so on.

So in this example you get two values at validity time 2016-12-01, 06:00.

The NetCDF format only supports a single, one-dimensional time dimension, so a specific time can not have two values.

This is why trying to retrieve this data in NetCDF format results in an error.

Possible workarounds

• Use the data's native GRIB format i.e. download the data in GRIB format and then convert the data file yourself following guidelines. GRIB format supports multiple data values at any one validity time.
• If you are only interested in the analysis, but not forecasts, download data only for step 0
• If you need overlapping forecast, download for each time option separately, for example:
  • first with time = 00:00 and all required steps
  • then with time = 06:00 and all required steps
  • then with time = 12:00 and all required steps
  • then with time = 18:00 and all required steps