Online retail sales in the U.S. will reach nearly $52 billion this holiday season, a 16 percent increase over last years numbers, according to a new report by Forrester Research.

The 2010 growth rate is twice the rate in 2009, when holiday sales grew by 8 percent during the global recession. Forrester defines the holiday shopping season as November and December.

“Consumers are showing a willingness to spend this season,” said Sucharita Mulpuru, Forrester Research vice president and principal analyst.

“And, almost universally, online retailers expect their holiday sales to increase this year over last year, showing industrywide optimism.”

The National Retail Federation is predicting a 2.3 percent increase in total holiday retail sales this year, indicating the overall strength of the online channel.

A recent Forrester survey of 4,700 US online consumers showed that they will make 37 percent of their purchases via an online channel this holiday season, compared with 30 percent in 2009. And 80 percent of retailers surveyed say that their gross online sales increased year over year for Q3, a likely indicator that the trend will continue.

As outlined in the new Forrester report, “US Online Holiday Retail Forecast, 2010,” 87 percent of US online buyers with a household income of $100,000 or more say they will spend the same or more online this year compared with last year, while just 13 percent say they plan to spend less.

This year will also see a boost in mobile’s role in completing a purchase — 18 percent of US online adults plan to use their mobile device to compare retail prices, and 16 percent expect to use their phone to locate a nearby store.

“Online retailers are primed to react to this year’s holiday trends,” said Mulpuru, “initiating aggressive promotional programs to drive holiday sales — exceeding even the discounts of previous years.”

“Retailers must expect heavy price-based competition this season and be prepared to play.”