From a tornado looming above Colorado to an orangutan using a leaf as an umbrella: National Geographic reveals its top pictures of 2015

National Geographic 2015 Photo Contest selects James Smart as winner from more than 13,000 submissions

Overall winner and category winners chosen from the three image groups: People, Places, and Nature

Winning photo shows a tornado looming above a Colorado farm site, taken after 15 days of storm-chasing

A massive tornado looms above a Colorado farm in the grand-prize winning photo of the National Geographic 2015 Photo Contest, chosen from more than 13,000 entries.

The photographer, James Smart of Melbourne, Australia, captured the image, titled 'Dirt,' after 15 days of storm-chasing.

Smart has been awarded $10,000 and a trip to National Geographic headquarters in Washington, D.C., where he will participate in the annual National Geographic Photography Seminar in January 2016.

'Dirt,' along with other winning photos and honourable mentions, can be viewed at natgeo.com/photocontest.

James Smart. Jaw-dropping, rare anti-cyclonic tornado tracks in open farm land narrowly missing a home near Simla, Colorado

The winning photo was taken last spring, outside of Simla, Colorado. Smart, along with his brother and some meteorologist friends, chased storms for 15 days before the captured the breathtaking moment.

'The tornado was slowly getting bigger as it picked up the dust and soil from the ground on the farmland,' Smart said.

'It wasn't moving very fast, so we kept getting closer as it tracked next to the home as you can see in the image.

'Driving down a Colorado dirt road, we were lucky enough to be on the west of the tornado, so it was front lit. This really helped to get great detail out of the image and the perfect light for the sky and foreground.'