Rare New River Tornado

This photo was taken September 23, around 1 pm, shortly before a rare meteorological event (click to enlarge). Our home town of New River, Arizona experienced its first tornado in the 20+ years we’ve lived here. Arizona ranks 13th in the continental United States for tornado frequency. From 1991–2010 we averaged only five per year. All occurred farther south in the state.

The photo shows what is called a shelf cloud. Follow that link to learn how they’re formed, and see a slideshow of one approaching New River from the south. They are fast-moving, ominous-looking, and almost always presage severe weather. The cloud was around 5 miles west of me when I shot this photo. 10 minutes later it had passed overhead and we were getting heavy rain.

Around this same time, area resident Fredda Psaltis captured the tornado on video. My thanks, Fredda, for sharing it on your Facebook page! And thanks for braving the storm to get that video. The strength of the wind is evident from the audio. I didn’t personally see this funnel. It was behind a mountain from my point of view, but I did see the shelf cloud that spawned it.

You can see the tornado was short-lived and not that violent. It caused no structural damage, but did scatter some trash and dust. Frankly, I’ve seen larger dust devils, but they’re a totally different phenomenon. Dust devils form from the ground up — tornadoes from the top down.

Compared to the Great Plains, Arizona doesn’t often have the meteorological conditions conducive to tornado formation: a mass of unstable humid air colliding with a mass of cooler dry air. Further, New River is in the foothills of the Colorado Plateau, near an escarpment along its southern boundary known as the Mogollon Rim. Although tornadoes can form in the mountains, they’re less likely when air flow toward the base of the funnel is disrupted by elevation changes.

This is not to say we don’t have violent weather — it’s just less frequent at our location. And when we do, the surrounding hills sometimes create a Venturi effect that adds 10-15 kph (6–10 mph) to whatever winds are being reported at lower elevations. During a monsoon storm 10 years ago my weather station measured a peak wind gust of 116 kph (72 mph).

Are you seeing any unusual weather at your location? If so, I’d like to hear about it. Photos or videos aren’t necessary, but provide valuable documentation. Climate change manifests in many forms and Sky Lights is the perfect venue for reporting its local effects.

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