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The combined impact of these changes has led to:
Slight improvement in NAM QPF scores,
A 5-10% reduction in NAM height, temperature and vector wind root-mean-square errors compared to radiosondes; positive impacts increase with forecast range,
A significant reduction in the false alarm rate for tropical storms.
The numerical instability observed off Newfoundland in ops NAM runs from 1-4 December was eliminated by these changes.