Piper Jaffray analyst Gene Munster stated in a note to clients Wednesday that he has increased his estimate of the number of iPhones he expects Apple to sell worldwide in its 4th quarter, from 4.1 million to 4.47 million.

In contrast, Apple sold only 1.12 million iPhones in the same quarter of 2007.

“Our 25 hours of counting iPhone sales in Apple retail stores throughout the country lead us to believe Apple is on pace to beat our previous estimate of 4.1 million iPhones for the September quarter,” analyst Gene Munster wrote.

The analyst is estimating that Apple sells an average of 95 iPhone 3Gs per day at each of its 188 U.S. retail stores.

“We believe Apple will sell 1.78 million units at its U.S. retail stores, and 0.90 million phones at U.S. AT&T locations”, Munster wrote. “Our estimate assumes each of the 2,200 AT&T stores will sell an average of 5 phones per day from the July 11th launch through the end of the September quarter”.

Munster’s team checked U.S. Apple stores for two weeks and in that period noted a 10-percent decrease in sales during the second week. For this reason Munster’s model accounts for the ever decreasing sales of the iPhone 3G.

On that basis Munster’s fourth quarter estimate assumes Apple retail stores will average 31 iPhone sales per day for the remaining 51 days in the quarter.

“We believe that our revision may be conservative and that Apple will meet our estimates,” he wrote. “The August 22nd launch in additional countries should provide another catalyst to sales.”