Tornadoes need the dry air of the Rockies, the moist air of the Gulf of Mexico, loft and wind shear to form the destructive funnels of their 10-minute lifespan.

Colorado ranks 15th in the nation in the average number of tornados per year, with 22 - compared with Texas's 139, Oklahoma's 57 and Kansas' 55, according to the National Oceanic and Atmospheric Administration.

The state ranks 38th in tornado deaths.

"We have a lot of tornadoes that rank on the lower end of the scale in terms of violence," said Tom Schlatter, a meteorologist with the Cooperative Institute for Research in Environmental Sciences in Boulder.

March tornadoes are very rare for Colorado - the plains have a 2 percent chance of a tornado this month. Of Prowers County's 1,850 violent storm events over the past 12 years, just eight happened in March, the National Weather Service said.

Nonetheless, weather conditions Wednesday were ideal for tornado formation, said John McGinley, a branch chief with NOAA's Earth Systems Research Lab in Boulder.

"It was a pretty tremendous day," McGinley said. "It was clear we had a fairly strong trough aloft, moving across the Rockies."

The Rockies' dry air met up with moist air moving northward from the Gulf of Mexico - the same conditions that created the state's Dec. 21 blizzard.

This time, though, the air from the Rockies wasn't only dry, but unseasonably warm - more like a May day.

And the air from the Gulf was very moist, creating tremendous instability as the systems collided.

"When these two air streams met, there was tremendous convergence," Schlatter said. "There was no place (for the air) to go but up."

That upward turn, together with the extreme instability of the warring systems, caused the rotation that begins so many destructive weather events.

About 5 p.m. Wednesday, when the sun's heat was at its maximum, exacerbating the temperature instability, dozens of storms, each a few miles wide, began to rotate.

"A lot of the storms Wednesday did nothing," McGinley said. "They just looked very vicious."

But some drew in updraft winds, spinning faster and faster, stretching out a column of rotating wind, causing what's called a mesocyclone.

"There were tons of tornadoes Wednesday," McGinley said.