readme: update data processing step example cmd; +note on subdomains

README.md

@@ -122,7 +122,7 @@ MLflow call example:
 
 ```
 mlflow run . --experiment-name <name>--env-manager=local \
--P lat_min=-25 -P lat_max=25 -P long_min=-280 -P long_max=80 \
+-P lat_min=-80 -P lat_max=80 -P long_min=-280 -P long_max=80 \
 -P factor=4 \
 -P CO2=1 -P global=0 \
 -P ntimes=100 \
@@ -175,6 +175,15 @@ the domains used for training. These are defined in
 coordinates. Note that at run time domains will be truncated to the size of the
 smallest domain in terms of number of points.
 
+*Note:* Ensure that the spatial subdomains defined in `training_subdomains.yaml`
+are contained in the domain of the forcing data you use. If they aren't, you may
+get a Python error along the lines of:
+
+```
+RuntimeError: Calculated padded input size per channel: <smaller than 5 x 5>.
+Kernel size: (5 x 5). Kernel size can't be greater than actual input size
+```
+
 #### Testing
 The [`testing/main.py`](src/gz21_ocean_momentum/testing/main.py) script runs the
 model testing stage. You select a trained model and a region (which should be