By Slash Lane

Published: 02:00 PM EST

With just one day to go before Apple announces the results of its fourth fiscal quarter, market research firm NPD is out with its preliminary sales data for the three-month period, leading one expert to suggest the company sold upwards of 2.8 million Macs systems.

"We have analyzed NPD data for all 3 months of the September quarter (July, Aug & Sep) [and] it leads us to a Mac number of between 2.7 million and 2.8 million," Piper Jaffray analyst Gene Munster told clients in a report Monday afternoon.

The analyst said those figures suggest Mac sales grew anywhere from 25 percent to 29 percent during the quarter, inline to slightly ahead of Wall Street consensus estimates which have the Cupertino-based company selling approximately 2.7 million systems on 25 percent yearly growth.

Specifically, Munster said NPD's data suggest Mac sales grew 19 percent year-over-year in September, down from 23 percent in August, and about 43 percent in July.

"The months of August and September were tough year-over-year compares, as new iMacs were introduced in August 2007, but new Macs were not introduced until [October] in 2008," he explained. "Also, it appears that the weak consumer environment is negatively impacting Apple's business."

As far as iPods go, Munster said the three full months of NPD data suggests Apple sold approximately 11 million units on 7 percent growth, which is slightly above expectations on Wall Street. Given lingering concerns that the company's digital media player business may be showing signs of weakness, the segment's outperformance in relation to the Street should be seen as a slight positive, he said.

For the quarter, the analyst is modeling Apple to report revenue of $8.368 billion and net quarterly profit of $1.06 billion, or $1.17 per diluted share, driven by sales of 2.8 million Macs, 11 million iPods and 5 million iPhones. He expects gross margin to come in around 32 percent.

"Despite the expectation for an extended consumer slowdown hitting the consumer electronics space, we believe Apple is well-positioned to weather the storm," he told clients. "The company has recently leveraged its unit volumes in the iPod, Mac, and iPhone businesses to lower prices moderately while generally maintaining margins."

Munster maintained his Buy rating and $250 price target on shares of Apple.

As usual, AppleInsider will offer comprehensive coverage of Tuesday's Apple earnings report and conference call.