In a rite of late summer as predictable as the start of football season, Apple's (AAPL - Get Report)  announcement of new iPhones typically triggers a round of promotions from AT&T (T - Get Report) , Sprint (S - Get Report) , T-Mobile USA (TMUS - Get Report) and Verizon (VZ - Get Report) . The offers for the iPhone 8, iPhone 8 Plus and iPhone X have already started, following Apple's event on Tuesday unveiling the new devices.

"The first two quarters after Apple releases a new iPhone model, Apple sees a massive sales peak," IHS Markit analyst Ian Fogg said of the carriers' annual competition for wireless subscribers. "It's doubly important for the U.S. carriers to be competitive as consumers upgrade their old iPhone with one of the latest models."

Sprint CEO Marcelo Claure tweeted an offer of half off the monthly lease for the iPhone 8 if subscribers trade in an iPhone 7.

2/7 @Sprint customers will save a TON of $$ - 50% off the monthly lease of the #iPhone 8 when you trade in your 7. Details tomorrow.

— MarceloClaure (@marceloclaure) September 12, 2017

Verizon is offering $300 off an iPhone 8 or iPhone 8 Plus when consumers trade in a qualifying phone (which phones qualify is unknown so far) and sign up for unlimited service. The carrier's payments start at $29.17 per month for a two-year lease on the iPhone 8, when customers pay the full $699.99 retail price, and $33.33 per month for the $799.99 iPhone 8 Plus.

T-Mobile provides a $300 discount for customers who trade in an iPhone 6 or a newer model, although it will apply the rebate to the iPhone X as well as the iPhone 8 and 8 Plus.

The #iPhoneX looks EPIC. & you know @TMobile will carry it! Plus we're giving you up to $300 off ANY new iPhone w/ trade-in!!

— John Legere (@JohnLegere) September 12, 2017

AT&T has taken a different approach, offering a 32GB iPad for $99.99 when customers sign a two-year contract for the iPhone 8 or 8 Plus. The carrier also highlights that it has recently packaged HBO for free in its unlimited plans, though customers would not need an iPhone to benefit from the promotion.

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The carriers may be missing an opportunity to use the Apple Watch Series 3, which has an LTE wireless connection, as a means to lure new customers, Fogg said. AT&T, T-Mobile and Verizon are charging $10 per month to provide wireless service to the Apple Watch 3, which must be on the same network as a user's iPhone. 

"What appears to be happening is the carriers are saying I can make money out of this and charging additional fees for the Apple Watch," Fogg said, suggesting that the telecoms are nickle-and-diming customers over the relatively small amount of data that the watch will use. "What I think they should be doing is using that as an acquisition driver to say come to us for the best iPhone experience and you can bring your Apple Watch."

The September iPhone promotions kick off months of competition between the wireless carriers that intensifies around the frenzied shopping in the long weekend following Thanksgiving.

Last year, T-Mobile USA got a jump on the competition by offering two free subscriptions to members on its family plan the Friday before Black Friday.

During the heated Thanksgiving weekend, T-Mobile added a trade in offer for the iPhone and other devices. Sprint and Verizon followed with similar offers, though AT&T did not make an iPhone offer.

The staggered launch of this year's iPhones creates an issue for the telecoms. 

"There are going to be two waves," Fogg said.

The iPhone 8 is available on Sept. 22, though shoppers can pre-order the device starting  Sept. 15.

Pre-orders for the iPhone X don't start until October 27, however, with the device available on Nov. 3.

Carriers have to make a somewhat awkward message to shoppers. "You can buy now, but if you want the best and you have the money please buy later," Fogg said. "That's a tricky piece of communications."

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