The first snowfall and probably the last wildflowers of the season.
Comet 21P/Giacobini-Zinner is a periodic comet with an orbital period of 6.6 years. It made its closest approach to Earth on September 10–11 when it was ~58 million kilometers distant. At that time it brightened to around magnitude 7—which is still too dim to be an unaided eye object. Binoculars, telescopes, or long-exposure photography is still necessary.
My first attempt to capture images was on September 15 when the comet passed in front of M35. Oddly enough, I was unable to clearly see the comet because of the large number of stars in the star cluster.
My second attempt was a few days later (September 18) after it had moved away from M35. This was a better setup. But my imaging wasn’t great. Perhaps the sky wasn’t as clear as I thought it was or my technique isn’t as good as I think it is. Either way, the results aren’t as sharp and clear as I hoped.
Still, it was fun—especially the second attempt. After setting up the tripod, aligning the equatorial mount, and getting [almost] sharp focus I let the camera run for over an hour taking 120 second exposures (followed by 120 seconds of Long Exposure Noise Reduction, LENR).
I was surprised (but should not have been) at how much movement there was in the position of the comet in just a bit over an hour. The video covers the time period from 0320 to 0431 MST.
I also used Deep Sky Stacker (DSS) to stack the individual images in which the software keeps the comet sharp while the stars have trails. Because of the 2-minute gaps between images, there are also gaps in the star trails.
During the 1-hour period in which the camera was on “autopilot” I was able to lie back and stare up at the sky. I saw about two dozen meteors during that period and many of them seemed to have origins near the constellation Orion. The Orionid meteor shower doesn’t peak for another several weeks (active from September 23rd to November 27th with a peak on October 21–22) but it’s possible these were early arrivals of that meteor shower.
Cumulus and Cumulonimbus
A search for wildflowers and thunderstorms brought me to Rogers Lake west of Flagstaff. It’s a lake only ephemerally during springs with heavy snow runoff. But it makes a grand place for photographs when a wide-open vista is desired. Earlier convective storms were pushing an outflow boundary southward with new convection developing on the boundary.
There was just enough vertical wind shear on this day to allow some storms to briefly exhibit supercell characteristics and deviate to the right —which brought this thunderstorm near the edge of the North Rim of Grand Canyon.
Fog and Smoke
Sometimes the unexpected can be magical. When fog forms in Grand Canyon the visitors may be disappointed but there is the potential for amazing photographs.
Smoke from the Obi Fire on the North Rim produced both amazing and dull conditions.
Sunset and Full Moon
Sunset after the storms can be amazing. And if there is a nearly full moon, things can get very interersting.
It’s early September and the summer monsoon pattern is beginning to fade away. Soon it will be time to start thinking about autumn colors on the peaks.
September 1 marks the first day of “meteorological autumn” and it started out with a severe weather event across portions of northern Arizona. Severe storms are more likely during what is often called the “transition season” as we make the switch from the North American Monsoon weather pattern into a fall pattern.
In the transition season the westerlies begin to push southward again as the large area of high pressure over the southwest weakens. Disturbances in the westerlies along with stronger jet-level winds can combine with copious amounts of residual tropical moisture to bring severe thunderstorms to the area.
A short-wave trough and moderate jet stream were present across Arizona at 1200 UTC 01 September. Monsoon moisture was also present. The first hint that something was up was the development of thunderstorms—some severe—before sunrise. This patch of storms moved to the east and northeast and, in its wake, left a pool of cooler air across northeastern Arizona along with an outflow boundary. Outflow boundaries can often play an important role in subsequent convection with increased severity and rotation as the storm moves across the boundary. (Maddox et al. 1980; Rasmussen et al. 1998)
Afternoon runs of the HRRR model showed storms developing along an east-west line across northern Arizona and that some of these would interact with that boundary, become severe and turn to the right moving southeast. And that’s pretty much what happened. Score one for the HRRR model.
Other storms produced very large hail with a report of 2.75″ hail in Holbrook and another of 2.00″ near Tolani Lake.
I was watching and photographing these storms from the southern portions of Wupatki National Monument. There was explosive vertical growth in these storms along with some generally unorganized rotation. The storm also developed a rear-flank downdraft. And I was able to hear the “hail roar” (i.e., a roaring sound that originates in the storm cloud caused by large hailstones hitting the ground or colliding in mid-air). I’ve occasionally heard hail roar in High Plains storms but never in Arizona.
Behind the storm, cold outflow dominated and low clouds and fog quickly developed across the low hills of Wupatki National Monument. A broad area of mammatus clouds was also present.
And the lightning was impressive.
The North American Monsoon arrived in northern Arizona during the first week of July—which is an average start date. Within just a few days, we quickly transitioned from Extreme Fire Danger to High—and within a week or two—to Moderate.
Summer monsoon season is my second storm chase season—the first is in late spring across the High Plains. Second season is more about lightning, clouds with dramatic scenery, and colors at sunset. This July has been a bit more challenging than other seasons but still successful.
Here are some photographs of storms and storm-related activity during July 2018.
Early stage Cumulonimbus
Outflow boundaries and arcus clouds
This complex of storms was moving westward across Wupatki National Monument. I had originally planned to photograph the system from the Doney Mtn. Picnic Area but the system arrived at that location before I did. So I retreated back to US-89 and the entrance to the Monument. Both of these images are panoramas that span the northeast through south. The San Francisco Peaks can be seen at the far right of both images.
Rainbows (and maybe a tornado?)
As convection approached a rainbow developed and I was busy trying to reset the camera to capture the full bow. Only later, when examing the images, did I notice what might be a vortex bisecting the rainbow. Because I did not see it in real time I cannot say whether there was any rotation. It may just be a random bit of cloud debris.
The best part of the thunderstorm season is trying to capture lightning. It’s more than just getting a photograph of lightning—it’s important to get lightning in an interesting location.
Sometimes I chase storms—other times they chase me. We were mountain biking on Observatory Mesa when this thunderstorm developed and enveloped the San Francisco Peaks. It was definitely time to turn around.
Sunset after the storm
And, of course, sunset after the storms can be pretty amazing,
Reflections in pools of water can produce interesting images. Several days of heavy rain resulted in ponds of water at Crescent Moon Picnic Area.
As is typical, rainfall amounts can vary widely over even just a few miles. Here is a map showing the rain gauge amounts for July on the east side of the San Francisco Peaks southward through Flagstaff and beyond. Amounts range from 2.5 to 14.5 inches.
August continues to bring thunderstorms, lightning, and flooding to northern Arizona.