The storm system that wreaked havoc across Orange County on Friday afternoon may have sounded like a tornado and felt like a hurricane, but in fact it was neither.
It was, in the peculiar vernacular of meteorology, an "extra-tropical cyclone" that packed neither hurricane-force winds nor tornadolike funnel clouds. Still, it was not something to be taken lightly.
"As we've seen, these things can cause damage," said Dan Bowman, a meteorologist for WeatherData, a weather-consulting firm that provides forecasts to The Times. "Especially when you get high winds, you can expect trouble."
The storm, which swept across Orange County and the Southland with a vengeance Friday evening, had moved out of the area and was over New Mexico by early Saturday. But forecasters said its tail winds could bring some light showers to the Southland late today.
To understand what happened and why, WeatherData's Bowman explained, it is necessary to understand the workings of an extra-tropical cyclone.
First, these types of cyclones rarely pack winds as strong as hurricanes, and they rarely if ever spawn funnel clouds and tornadoes.
"All it is is a low-pressure system that developed outside of the tropics, in this case just off the West Coast," he said. "It strengthened as it moved in, pulling a lot of wind into it. We had predicted the rain, but not the winds.
"It's like pulling the plug of a bathtub drain and all the water swirls down the drain. But in this case, it is air that is being drawn into the center of the storm. That's similar to a hurricane, but hurricanes develop over warm water, and this one didn't. That's why it's a cyclone and not a hurricane."
What was unusual Friday, Bowman said, was the strength of the storm once it hit the coast.
"We couldn't predict just how much this storm was going to intensify right before hitting Southern California, and it did intensify greatly," he said.
Winds were gusting up to 55 m.p.h. in Newport Beach, far shy of minimal hurricane strength of 73 m.p.h. but well within tropical storm strength. But in other areas, the winds were much weaker.
"That's because of all the mountains and valleys and the different terrain you have across Southern California," he said. "That can affect wind speed. It just happened that some areas got strong winds and others didn't. Obviously, places closer to the coast, where there is less friction to interfere with the storm system, had stronger winds.
"The mountains and hills tend to break up the wind and disturb the wind flow."
Although not rare, Bowman said, extra-tropical cyclones do not normally develop as far south as Southern California.
"You mainly see them in Northern California, Oregon and Washington," he said. "They are not uncommon, but you don't see a lot of them."
Bowman said he understood the suspicion of some residents that they had been hit by a tornado or hurricane.
"Wind is wind, and when it's really blowing it doesn't matter what you call it," he said. "And if that storm had produced 74 m.p.h. winds we could have said it produced hurricane-strength winds, but in truth it wasn't a hurricane. And no, there weren't any tornadoes."