Tag: weather

Yet another tornado for Northern Arizona

Last week another tornado moved across northern Arizona. The damage produced by this tornado was confined to a small area and was nothing like the tornado outbreak of 06 October 2010.

What makes this tornado interesting is where it occurred. The tornado formed just west of the San Francisco Peaks and then moved up the west flank of Humphreys Peak. Damage was isolated along the early portion of the path at around 9000 feet. As it moved up the mountain, damage increased in intensity and coverage with the peak damage occurring near 9800 feet. Farther up the mountain isolated damage continued until the tornado dissipated near 10500 feet.

The worst damage occurred as the tornado crossed the Humphreys Trail just a short distance from the trail register. In the first few days after the event travel along this section of the trail can best be characterized as challenging. Climbing over and under downed trees — and around others — certainly slows the hiking pace.

Somewhere under all those trees is the Humphreys Trail.
Somewhere under all those trees is the Humphreys Trail.

This is not the highest elevation tornado of record. That belongs to a tornado that occurred in the Sierra Nevada mountains a few years ago with evidence of damage at elevations above 12000 feet.

The  limited damage inflicted upon the mountain might never have been noticed if it had not passed over a heavily used hiking trail. Now that’s serendipity. Or bad luck.

Nobody saw the tornado so all we have to go on is the radar data. And according to that information the event occurred between 5:25 and 5:35 pm on 14 September 2011.

Lightning and Mammatus: The beauty of thunderstorms

The North American Monsoon is bringing thunderstorms to the southwest United States including northern Arizona. You would think that with almost daily thunderstorms it would be easy to shoot great images of lightning and thunderstorms. Well, not always…

One of the characteristics of the rainy season in the higher elevations of northern Arizona is that as the storms develop in the late morning or early afternoon it quickly becomes overcast so that it is difficult to see the individual storms. It is equally difficult to photograph lightning because it is often raining over large areas obscuring the view of the lightning.

Lightning in Sunset Crater National Monument.
Lightning in Sunset Crater National Monument.

So I was particularly pleased when we had two days in a row in which I was able to photograph lightning and actually see the thunderstorms. The lightning was photographed in Sunset Crater National Monument overlooking the Bonito Lava Flow; the mountain that it is striking is O’Leary Peak. There is a fire lookout station at the summit of the peak and I’m certain they get their fair share of close bolts.

Sunset colors on an Arizona thunderstorm.
Sunset colors on an Arizona thunderstorm.

The following day proved equally photogenic. This thunderstorm was photographed in late afternoon and is quite dramatic with mammatus clouds visible from the anvil region of the storm.

If only everyday was as photogenic as these two.

Early winter ice and snow in Pumphouse Wash

Not too far south of Flagstaff lies Pumphouse Wash, a beautiful and narrow canyon that cuts through the Kaibab limestone and Coconino sandstone. The canyon drains from the upper elevations of the Mogollon Rim into the headwaters of Oak Creek. Most of the time Pumphouse Wash is dry with occasional pools but it can run very full during the spring snow melt and after heavy summer thunderstorms.

Shortly after a light snowfall in late November I took a walk up the wash hoping for some interesting photographic possibilities with snow and ice. I wasn’t disappointed. The first image shows a small pothole scoured by the erosive actions of the occasional flood waters. It was filled nearly to the brim with rain and snow melt, perfectly blended with leaves and pine needles, and then frozen in time.

A mixture of rain and snow melt with leaves and pine needles all frozen in time.
A mixture of rain and snow melt with leaves and pine needles all frozen in time.

Elsewhere in the canyon a sycamore tree had shed its leaves among the boulders of the wash and upon these leaves some snow was still in place.

Snow atop fallen sycamore leaves in Pumphouse Wash.
Snow atop fallen sycamore leaves in Pumphouse Wash.

Although it was a sunny day in northern Arizona very little of that sun was able to penetrate into the confined narrows of Pumphouse Wash. And I had the canyon to myself that day.

White Sands Reflected in Pools of Water

We recently took a trip to White Sands National Monument in New Mexico. The weather forecast that day called for increasing clouds and a chance of thunderstorms — some possibly severe — by late afternoon. Normally, this would be a deterrent to those wishing to visit this wonderful place but since I enjoy photographing thunderstorms and severe weather this was an opportunity not to be missed.

Rainbow over White Sands National Monument.
Rainbow over White Sands National Monument.

We arrived at WSNM in mid-afternoon and the clouds were beginning to fill the sky. We were soon rewarded with a rainbow stretching across the parabolic dunes on the edge of the dune fields. As that first storm moved away, other storms began to develop back to the west. I set up the camera to take lightning photographs and was rewarded with a couple of pretty good shots.

Late afternoon cloud-to-ground lightning over White Sands National Monument.
Late afternoon cloud-to-ground lightning over White Sands National Monument.

But the really wonderful part came the next morning. Those afternoon thunderstorms continued through the evening and into the night and produced about one and a half inches of rain across the sands. And in the bright blue sky of the following morning we found shallow lakes of up to a few inches deep scattered across the sands as a result of the heavy rainfall. The reflections of the sand dunes and other vegetation in these ephemeral lakes was simply delightful.

Reflections in the shallow lakes produced by heavy rainfall across White Sands National Monument.
Reflections in the shallow lakes produced by heavy rainfall across White Sands National Monument.

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.