Tornado outbreak in northern Arizona

While tornadoes are not as common in Arizona as in, say, the mid-western United States, neither are they rare. In an average year, about six tornadoes are reported in Arizona. It’s a near certainty that this number is an undercount of the actual number of tornadoes that occur. Because much of Arizona is sparsely populated, it’s possible — likely, even — that many tornadoes are not seen and thus, not reported.

So, while it may seem like the tornado outbreak in northern Arizona that occurred on October 6, 2010, was an extreme event, we can not be certain that it was. We can only be certain that it was one of the most extreme “reported” events.

At least eight tornadoes have been confirmed. Based on a review of the Doppler weather radar data there is a reasonable probability that additional tornadoes occurred in the vast Ponderosa forests of northern Arizona and the damage paths have not yet been noted and surveyed. While conducting a formal damage survey on October 7 and 8 for two of the already confirmed tornadoes, we found additional tornado damage paths that had not yet been previously identified.

Recent research has identified a repeatable weather pattern that is responsible for a significant fraction of tornadoes in northern Arizona. As that weather pattern began to develop, warning forecasters began to carefully monitor Doppler radar looking for signatures of severe thunderstorms. And when these signatures appeared, they quickly issued Tornado Warnings. It is almost certain that these warnings minimized injuries in the paths of these tornadoes.

Damages homes from the Bellemont, Arizona, tornadoes on October 6, 2010.
Damaged homes from the Bellemont, Arizona, tornadoes on October 6, 2010.

Flattened forest of Ponderosa Pine in northern Arizona from the tornadoes on October 6, 2010.
Flattened forest of Ponderosa Pine in northern Arizona from the tornadoes on October 6, 2010.
Forest Service crews quickly cleared treefall from Forest roads.
Forest Service crews quickly cleared treefall from Forest roads.

Some of the research on tornadoes in northern Arizona can be found at these links sponsored by the American Meteorological Society:

Blanchard, D.O., 2006: A cool season severe weather episode in northern Arizona. Preprints 23nd Conference on Severe Local Storms, St. Louis, MO., Amer. Meteor. Soc.

Blanchard, D.O., 2008: Synoptic environments associated with tornadoes in northern Arizona. Preprints 24th Conference on Severe Local Storms, Savannah, GA., Amer. Meteor. Soc.

Blanchard, D.O, 2010: Forest damage associated with tornadoes in northern Arizona. Preprint 25th Conference on Severe Local Storms, Denver, CO, Amer. Meteor. Soc.

High-altitude desert camping

Back in August we took a vacation to California to do some mountain biking. On the first day, we travelled across Arizona and Nevada at a leisurely pace. It was our goal to reach some national forest lands and find a Forest Service campground for the night. Didn’t work out that way. We ran out of daylight long before we reached any forest lands so as twilight was settling in we started driving down secondary roads and then dirt roads until we were able to set up a quick campsite for the night.

The spot we chose was far enough from the highway and other roads that we heard and saw no traffic and we felt like we were in the middle of nowhere. To our west were the White Mountains and Boundary Peak, the highest mountain in Nevada. To our south was the small community of Fish Lake Valley. What a beautiful location!

For the remainder of the trip we stayed in busy Forest Service campgrounds or motels. None of them can compare with the delightful solitude of this location.

Time to get up! Dawn of a new day in the high deserts of western Nevada.
Time to get up! Dawn of a new day in the high deserts of western Nevada.
High desert camping in Nevada with early morning light on the White Mountains to our west
High desert camping in Nevada with early morning light on the White Mountains to our west
Early morning light on the White Mountains in Nevada.
Early morning light on the White Mountains in Nevada.

In another post I’ll talk about the highlights of that trip.

Late summer rain showers and rainbow

The past few weeks have produced some very fine late summer weather across northern Arizona. Warm days…cool nights…light winds…and clear blue skies day after day.

But that gets boring after awhile so I was happy that we had a change of weather this week. Copious amounts of tropical moisture have surged northward across Arizona just as a weak Pacific weather system and cool front swept eastward across the state. The result was a night and day with on-again, off-again rain showers and a few thunderstorms.

Rainbow and anti-crepuscalar rays over northern Arizona.
Rainbow and anti-crepuscalar rays over northern Arizona.

Late in the day the clouds were pushing to the east and the sun was beginning to shine in the west producing the right conditions for a rainbow and for anti-crepuscular rays. AC rays are those alternating bands of light and dark seen in the opposite direction of the sun. The Atmospheric Optics web pages describe these and many more optical phenomena.

Rainbow over the San Francisco Peaks.
Rainbow over the San Francisco Peaks.

This was only a partial rainbow and the other end was located in the midst of the San Francisco Peaks north of Flagstaff.

A very nice end to an interesting weather day.

International Space Station transit at twilight

The other day the International Space Station (ISS) made a transit of the western sky during twilight. Low on the horizon was the planet Venus with the ISS streaking across the sky above. I’ve been shooting images of the ISS for a year or two but think this is one of the best. It works for a number of reasons. One is the bright twilight on the horizon deepening into dark night sky above. The planet Venus — and its reflection in the water — add a counterpoint.

To create this image I set the camera on continuous shoot and then used the remote release to start. The images are ISO 200, f/4.0, 28mm wide angle lens, and 10s exposures. Five images were taken so this is 50 seconds of transit.

I opened all five images in Photoshop with each image a layer. Because 50 seconds is long enough for stars to leave trails across the sky — even with a wide angle — I wanted to only use one sky layer. In the other four layers I masked the stars and sky and left only the track of the ISS. The result is sharp points for the stars and Venus and a smooth track for the ISS.

Twilight transit of the International Space Station (ISS).
Twilight transit of the International Space Station (ISS).

To get daily updates on transit times of the ISS — and other space satellites — I use the following two web sites:

Spaceweather.com (http://www.spaceweather.com)

Heavens-Above.com (http://www.heavens-above.com)

Perseid meteor shower

Did you get a chance to view the Perseid meteor shower this year? It peaked on the evening of August 12-13 but meteors were visible for many days preceding the peak. With the moon just a few days past new and setting early the skies were very dark for optimal viewing. A maximum rate of more than 100 meteors per hour has been reported with this years event. This compares with a more typical maximum rate of about 50-80 per hour. So this was a better than average event with higher numbers as well as very dark skies.

Triple planetary conjunction of Venus, Mars, and Saturn along with the crescent moon.
Triple planetary conjunction of Venus, Mars, and Saturn along with the crescent moon.

But to make things even better there was a three-way planetary conjunction taking place at the same time. In the western sky after sunset an observer could see the planets Venus, Mars, and Saturn close together along with the crescent moon.

For the meteors, I used a 28mm wide angle lens, ISO 3200, f/4.0, and 30s exposures. I set the camera to continuous shooting mode and let it run until the card filled a few hours later. I then reclined on a lounge chair with a sleeping bag draped over me.

Two Perseid meteors streak across the early morning sky a few days before the peak.
Two Perseid meteors streak across the early morning sky a few days before the peak.
Perseid meteor passes by the constellation Pleiades.
Perseid meteor passes by the constellation Pleiades.
Perseid meteor streaks across the Milky Way with the San Francisco Peaks on the horizon.
Perseid meteor streaks across the Milky Way with the San Francisco Peaks on the horizon.

Even though I saw a large number of meteors with my eyes — and some of them were spectacular long-path events with residual debris trails — the camera captured far fewer because the field of view of even a wide angle is not wide enough to view the entire sky