Hi,
It is a long time since I last looked at this script.
If you have set $getmetar = false;
then // if set to false will Use Cumulus (Zambretti Forecast) data ONLY
applies. The Zambretti forecast is produced by Cumulus itself and there will be no interaction attempted with NOAA.
However, you should be aware that the Zambretti forecast is very simplistic and unreliable.
Also, you would need to set ( i.e. tick the box for ) the Cumulus option
[] Use Cumulus forecast
Use the Zambretti forecast generated by Cumulus
This is under Settings / Station Settings / Forecast.