Monday, August 05, 2013

Raining Cats and Dogs...and Lies

A lot of movie buzz this summer has centered on SyFy’s I-don’t-even-know-what-to-call-it film Sharknado. And although it probably left a great many thinking “we’re gonna need a bigger plot,” I’m not actually here to criticize its style. (There’s no point; the movie wasn’t supposed to be serious, I don’t think.) I am, however, here to comment on the obvious: the plausibility of a real-life sharknado.

Obviously, sharknadoes are nothing more than a fish tale. (At least, I hope that’s obvious.) But that is not to say that weather and the animal kingdom can’t collide. In fact, animals much smaller than sharks sometimes do become part of the weather.

Though it was no tornado, in March of 2006, a supercell in southern Texas ingested thousands of bats into its updraft as a consequence of having formed in the early evening, when bats are coming out for food, in a region where there happens to be many bat caves.

The radar actually picked up the plumes of bats rather well:

As far as I know, no one in this rural area reported seeing bats fall from the sky, but it’s at least plausible that a few of the many that were drawn in by the storm’s inflow came down with hail and heavy rain in the storm’s downdraft.

SPC’s “Cool Images” page has a write-up on the event with links to more images.

But if when it comes to animals raining from the sky you want hard evidence, look to the squishy situation in Serbia, where supposedly frogs rained from the sky in the village of Odzaci in June of 2005. All of the mentions of this event that I could find online sourced the same Serbian newspaper, the Belgrade daily Blic, which is apparently a tabloid.

Meanwhile, more reputable sources have reported fish falling from a thunderstorm in the northern Australian town of Lajamanu as recently as February of 2010.

Although uncommon, it is possible for strong winds in a thunderstorm or tornado to empty a small pond and lift whatever is living in that pond along with the water into the storm.

So while sharknadoes only exist in moviemaker’s imaginations, it is at least possible that other types of animal-prefix-nadoes could happen.

But what about movies that have at least tried to be serious about referencing or including weather in their plot lines?

One film that comes to mind is The Perfect Storm. It is based on the real-life “perfect storm,” a conglomerate of Hurricane Grace and another extratropical Low that drifted off the New England coast for several days in October of 1991.

The film’s climax occurs when the Andrea Gail is swallowed by one enormously large wave. While I don’t believe anyone knows for sure exactly what happened in the final moments of the Andrea Gail, such a wave is at least plausible, despite Gracie never being a major hurricane.

Wave size is a function of the size of a storm’s wind field more than it is of the actual wind speed itself. The duration of wind in one place also adds to wave height as the water below the storm continues to accumulate kinetic energy in the same place. So the perfect storm, which was large and slow-moving, could very well have produced a wave that large.

And while The Perfect Storm may be the high point in our discussion of movies’ weather accuracy, The Day After Tomorrow featured one scene that at least wasn’t as completely off base as Sharknado.

That said, it’s still pretty out there.

The scene where multiple tornadoes strike Los Angeles holds onto a shred of truth in that it is possible for multiple tornadoes to strike in one area. Sometimes this occurs when a violent tornado undergoes “vortex breakdown,” resulting in one circulation with multiple vortices. Other times, this happens when a very strong tornado’s parent mesocyclone is so strong that its boundary with the ambient environment causes an anticyclonic (meaning it spins clockwise, in the Northern Hemisphere) satellite tornado to form and rotate around the main tornado.

However, this scene clearly depicts multiple separate tornadoes in the same area, which is not one of the above two scenarios.

Then of course there’s the obvious fact that Los Angeles essentially never has the conditions necessary for supercells to form. But I suppose the odds of multiple tornadoes striking the city are still better than the odds of even one sharknado hitting L.A.

But even in a place supercells are likely form, like Oklahoma, movie-makers still manage to screw things up. I could write an entire article just on what Twister got wrong, but for now, all I’ll say is that by definition it impossible to rate tornadoes on the Fujita Scale while they are happening. So when the gang, eating at Meg’s, discusses how the tornado they just saw was a strong F2, or maybe an F3, that’s more crow than a supercell full of bats.
The bottom line? It’s almost always better to be skeptical of Hollywood meteorology.