In a note to clients — as reported by “AppleInsider” ( — Piper Jaffray analyst Gene Munster says the Mac line-up is demonstrating 13% year-over-year growth in the first two months of the current quarter.

Basing this on the latest data from the NPD research group (, he says the numbers are “soft” compared to what is expected of Apple for the December quarter. However, that data only represents Apple’s Mac sales in the U.S., and doesn’t include the platform’s worldwide growth.

Investors generally expect Apple to sell about 5.2 million Macs in the December quarter, which would translate to year over year growth of 25%. The NPD data showed desktop units up 5%year over year in the month of November, while notebooks were up 9 percent from 2010.

Munster projects 5.1 million and 5.3 million Mac sales in the December quarter. That would be a record for the company, notes “AppleInsider.”

“We believe international Mac sales are likely growing faster than domestic Mac units (and NPD does not track international Mac sales),” Munster wrote. “Net-net, we are maintaining our range of 5.1m-5.3m, or 23%-28% (year over year) growth.”