By late morning it was evident that convection was going to be interesting. Updrafts were quite vigorous and there was pileus atop many updrafts.
I thought about photographing storms but got sidetracked. Then I heard the first Severe Thunderstorm Warning on NOAA Weather Radio. Less than an hour later a Tornado Warning was issued.
I looked at the radar data for the warned storm but was unable to see a clearly defined mesocyclone or tornado vortex signature (TVS). As it turns out, this was a non-supercell tornado (NST), sometimes called a landspout—and landspouts are often difficult to detect by radar.
This warning finally got my attention. A short while later, I headed out the door to see if any other storms would be as interesting as this one. I drove east towards some existing convection near and north of Winslow—stopping frequently to take photographs.
New storms then began to form back to the west and I set my sights on these. By this time, I had moved back west to the Two Guns exit on Interstate 40. Two Guns is now a ghost town and there are several old and interesting buildings in the area. I set up so that I could photograph both the old buildings and the storm. That worked out well.
Then it was time to move to the north side of I-40 so I could get some photos without any buildings in the way. You know—just in case a tornado formed.
No tornadoes were observed although for a brief period the visual appearance and radar depiction suggested that the storm was developing supercell characteristics and had some rotation.
I shot both still images and video. Unfortunately, the dynamic range from the brilliantly lit updraft to the dark shadowy areas elsewhere was too much for the video and portions of the updraft were overexposed.
Still, the video shows some interesting evolution. Thirty minutes (1711–1741 MST) of raw video was compressed into ~18 seconds.
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.
A previous post displayed photographs of storms and weather that occurred during July of this year’s North American Monsoon. Here are photographs from August (plus the first day of September).
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.
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.