Spurred by the iPhone 4S launch, several analysts expect sales of Apple’s iPhone lineup to explode during the fourth quarter of this year. “The timing of the 70 [international] launches could have some impact on sales ahead of the launch, the US/International split, and hence, our estimates look conservative,” UBS analyst Maynard Um said in a recent note to investors. “A similar 27.5 percent U.S. / 72.5 percent international split from this quarter would imply 42.5 million units in CY4Q or an upside of 14.5 million iPhones.” Apple shipped 17.1 million iPhones during the fiscal fourth quarter, and the lower-than-expected sales were blamed on rumors and anticipation ahead of the iPhone 4S launch. Um predicts a huge turnaround for Apple in the fourth calendar quarter, and of course he isn’t alone. The “resoundingly successful” iPhone 4S launch is expected to result in a big holiday season for the Cupertino-based company, Ticonderoga Securities said in a recent note.