Typhoon Haiyan became a category five storm before making landfall. Hurricanes of this magnitude are not uncommon in the western Pacific Ocean.
According to Colorado State University's hurricane expert, Dr. Phil Klotzbach, there were two main ingredients that led to the intensification of Typhoon Haiyan.
He said the storm tracked over an area of deep, warm water. That provided the storm with plenty of fuel for intensification.
Haiyan was also located in an area of very light, uniform winds.
"It also did not encounter much vertical wind shear, and that's the change of wind direction with height in the atmosphere. Tropical cyclones like to have as little of that change in wind direction as possible," said Klotzbach.
Developing in an area primed for intensification, Haiyan grew in strength and diameter. The size of the storm is what sets it apart from other category five hurricanes, as it was able to impact a larger area for a longer duration.
In comparison to the Atlantic Ocean, the Western Pacific is more conducive for hurricane intensification.
In the past 100 years, three hurricanes have made landfall in the United States as category five storms: the 1935 Labor Day Hurricane, Hurricane Camille of 1969 and Hurricane Andrew of 1992.
The most recent Atlantic Hurricane Season has been the quietest season since 1982 with only two hurricanes developing, explained Klotzback.
"If you look globally, I believe we're sitting at about 60 to 65-percent of a normal season, so it's been a fairly quiet year globally for tropical cyclones," he said.