Accelerated December 2006 NAM Changes - Summary http://www.emc.ncep.noaa.gov/mmb/namchanges_dec2006/nam_upgrades.nov2006.html

• 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.