Ever since I visited the local wind farm in 2007, I have been interested in wind turbines, despite their unproven problems. Last year, I blogged about the dangers of wind turbines in the paths of hurricanes. Today (hat tip to Michael Wade Moss) this video surfaced from the November 7 tornado outbreak in Oklahoma. Click here to start the video at the part where the tornado starts moving over the wind farm, or skip to 2:21 below.

This is something I've always been interested in seeing -- how a wind turbine would stand up to a twister. Basehunters was lucky to get this video. It doesn't appear to be a large, particularly strong vortex, but this tornado has not yet been rated on the EF Scale, according to the NWS. As Michael says in his blog, the turbines don't appear to be damaged, and I couldn't find any reports that they were, but I suspect there could be less obvious internal or external damage. Ironically, the November 7 tornadoes also destroyed a weather station in Oklahoma.

Wind turbines are suppose to brake their blades at the "cutoff speed" (usually 40 mph) or otherwise mitigate potential damage from high wind speeds. It's possible we're seeing that in the video (that's why some are spinning and others aren't, and they appear to turn into the wind). However, I would guess that those procedures are not tested for tornadoes.

As recently as May this year, no tornadoes were known to have ever hit a wind farm. This July, however, severe thunderstorms mangled wind turbines in Minnesota, according to public radio. The photo above is courtesy the Lincoln County, Minnesota Emergency Management Agency, who says 6 wind turbines were severely damaged.

Officially, there were storm reports from around the area, including winds up to 70 mph, but none mentioned the damage to the turbines specifically. The NWS has a photo of damaged grain bins near wind turbines, west of Lake Benton (circled in red below), but they don't mention the damage to the turbines.

Of this damage reports in general, they say "In addition to the two tornadoes, widespread wind damage of 80-100 mph caused significant damage between Wentworth, SD to Marshall, MN." So, it's likely this was straight-line wind damage. It's possible that those could be more dangerous than a tornado if they hit at a perpendicular angle to the blade field. Oddly enough, this storm report came out on five years earlier in the same county: June 24, 2006: "THUNDERSTORM WIND DAMAGE: BLADE OF WIND TURBINE SNAPPED OFF NEAR THE INTERSECTION OF US HIGHWAY 14 AND MN 271."

CAPTION: Me standing next to a wind turbine blade at the Allegheny Ridge Wind Farm in 2007.

MORE WEATHERMATRIX WIND FARM BLOGS:

- The Google Mid-Atlantic Wind Farm Vs. Hurricanes
- Weatherwise Mag Busts Wind Power Myths
- False Tornado Warnings From Wind Farms?
- Wind Power on the Outer Banks
- Photos: Visiting the Allegheny Ridge Wind Farm

Of course, stranger things have happened. Wind turbine damage in the U.K. in 2009 was initially blamed on a UFO, but later was reported to have been a mechanical failure. In other wind turbine news, a new kite-like turbine, which locates the highest winds more efficiently, has been proposed.

CAPTION: A rainbow is visible looking West from Palm Springs, Calif. on Monday, Jan. 28, 2008 next to an array of wind turbines. (AP Photo/Sandy Huffaker).

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