You may not have noticed, but the U.S. economy is on a tear.

Or at least that's what an economic model at the Atlanta Federal Reserve is showing.

Based on recent economic data, the gross domestic product is headed for a 4.5 percent annualized growth pace in the fourth quarter, according to the Atlanta Fed's model, called GDP Now. That would be a sharp pickup from the third quarter, which the government's initial estimate pegged at a 3 percent growth rate.

The Atlanta Fed model looks at multiple, current measures of economic activity and uses them to forecast where the overall economy is headed.

The latest estimate for fourth-quarter GDP growth is much faster than the 2.9 percent rate the model showed Monday, the Atlanta Fed said. The improved outlook came even as data on U.S. factory output eased off a 13-year high in October.

The GDP Now forecast has roughly tracked the government's initial estimate of the U.S. economy. The Bureau of Economic Analysis will publish its next "advance" estimate on Jan. 27 for the last three months of this year.