Fog and Atmospheric Optics

Fog with a Glory, Brocken spectre, and two segments of a fogbow.

In the wake of a departing low pressure system I expected that there might be areas of dense fog in the morning. I awoke well before sunrise to look at satellite images to see if fog was developing. And, yes, there were some hints that fog was present. Good!

GOES-16 IR satellite image from ~5 a.m. showing large areas of fog across northern Arizona.
GOES-16 IR satellite image from ~5 a.m. showing large areas of fog across northern Arizona.

I left the house around 6 a.m. and headed east on Lake Mary Road. A few miles outside of town I ran into fog. Visibility dropped quickly to around 1/4 mile. Drive carefully!

My destination was the Mormon Lake Overlook. I had some success last winter at this site with a similar fog situation. As I approached the overlook the fog lifted becoming a low cloud deck above me. Hmmmm….not quite what I wanted. Ahead, I could see the edge of the cloud/fog. As I made the final approach to the overlook the road gained a bit of elevation and, suddenly, I was above the cloud/fog deck. Wonderful.

The sun had not yet risen but it was light enough to see that there was a shallow layer of fog covering the Mormon Lake basin. Moments later the sun began to rise through the dense fog.

Sunrise through the fog.
Sunrise through the fog.
Layers of fog at sunrise.
Layers of fog at sunrise.

With the sunrise a Glory and Brocken spectre became visible. Moments later, two short segments of a fog bow appeared. Also visible is a shadow of the overlook.

Fog with a Glory, Brocken spectre, and two segments of a fogbow.
Fog with a Glory, Brocken spectre, and two segments of a fogbow.
Fog begins to dissipate across the Mormon Lake basin.
Fog begins to dissipate across the Mormon Lake basin.

As the fog began to dissipate over Mormon Lake, I headed towards Anderson Mesa Station (home to several telescopes) because it is high enough to be above the fog. But first, along the way, the road dropped down into the fog and I saw this fog bow.

Fogbow near Lake Mary.
Fogbow near Lake Mary.

Finally, atop Anderson Mesa I once again was above the fog and able to photograph a Glory—this time projected onto trees with autumn colors.

Another glory and Brocken spectre projected onto fall foliage.
Another glory and Brocken spectre projected onto fall foliage.

Finally, here is a time-lapse of the fog over Mormon Lake that includes the Glory and the right-hand side of the fog bow.

Edit: Replaced GOES-16 visibile image with IR image.

Severe Thunderstorms Near Two Guns

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 convection forming to the WNW of Two Guns, Arizona. (1651 MST 21 October 2018. )
New convection forming to the WNW of Two Guns, Arizona. (1651 MST 21 October 2018. )

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.

Strong thunderstorm N of Two Guns, AZ. (1707 MST 21 October 2018)
Strong thunderstorm N of Two Guns, AZ. (1707 MST 21 October 2018)

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.

Supercell thunderstorm north of Two Guns, AZ. (1714 MST 21 October 2018)
Supercell thunderstorm north of Two Guns, AZ. (1714 MST 21 October 2018)

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.

As the storm moves to the ENE light from the setting sun illuminates the foreground. (1725 MST 21 October 2018)
As the storm moves to the ENE light from the setting sun illuminates the foreground. (1725 MST 21 October 2018)
Sunset colors illuminate the storm as it moves to the ENE. (1729 MST 21 October 2018)
Sunset colors illuminate the storm as it moves to the ENE. (1729 MST 21 October 2018)
Sunset colors. (1733 MST 21 October 2018)
Sunset colors. (1733 MST 21 October 2018)
Cumulus convection takes on pastel colors as the sun sets. (1742 MST 21 October 2018)
Cumulus convection takes on pastel colors as the sun sets. (1742 MST 21 October 2018)

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.

 

A look at Comet 21P/Giacobini-Zinner

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.

First attempt at Comet 21P/Giacobini-Zinner.
First attempt at Comet 21P/Giacobini-Zinner.

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.

Comet 21P/Giacobini-Zinner.
Comet 21P/Giacobini-Zinner.

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.

Comet 21P/Giacobini-Zinner.
Comet 21P/Giacobini-Zinner.

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.

Arizona Monsoon Clouds—August 2018

The setting sun lights up rain curtains as a brilliant lightning bolt strikes behind Wukoki Pueblo in Wupatki National Monument.

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.

Outflow boundary and convection over Rogers Lake with the San Francisco Peaks in the distance.
Outflow boundary and convection over Rogers Lake with the San Francisco Peaks in the distance.
A distant cumulonimbus can be seen from the Doney Mountain Picnic Area near Wupatki National Monument.
A distant cumulonimbus can be seen from the Doney Mountain Picnic Area near Wupatki National Monument.
Thunderstorms move across Grand Canyon with low clouds clinging to the higher points and buttes.
Thunderstorms move across Grand Canyon with low clouds clinging to the higher points and buttes.

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.

A strong thunderstorm over the North Rim of Grand Canyon is reflected in a small pool of water.
A strong thunderstorm over the North Rim of Grand Canyon is reflected in a small pool of water.
A weak, late afternoon thunderstorm is backlit by the setting sun.
A weak, late afternoon thunderstorm is backlit by the setting sun.

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.

A long-lived cluster of thunderstorms east of Grand Canyon pushed a cool, moist outflow into the canyon producing areas of fog near the South Rim.
A long-lived cluster of thunderstorms east of Grand Canyon pushed a cool, moist outflow into the canyon producing areas of fog near the South Rim.
More fog in Grand Canyon.
More fog in Grand Canyon.

Smoke from the Obi Fire on the North Rim produced both amazing and dull conditions.

Smoke from the Obi Fire on the North Rim creates a colorful sunset.
Smoke from the Obi Fire on the North Rim creates a colorful sunset.
Smoke from the Obi Fire fills Grand Canyon and reduces visibility.
Smoke from the Obi Fire fills Grand Canyon and reduces visibility.

Sunset and Full Moon

Sunset after the storms can be amazing. And if there is a nearly full moon, things can get very interersting.

A backlit thunderstorm at sunset over Grand Canyon.
A backlit thunderstorm at sunset over Grand Canyon.
Post-sunset colors illuminate the underside of a dissipating shower.
Post-sunset colors illuminate the underside of a dissipating shower.
Dissipating cumulus clouds at sunset with O'Leary Peak in the distance.
Dissipating cumulus clouds at sunset with O’Leary Peak in the distance.
Dissipating showers are backlit by the setting sun.
Dissipating showers are backlit by the setting sun.
The nearly full moon illuminates the inner canyon as twilight fades behind a distant thunderstorm.
The nearly full moon illuminates the inner canyon as twilight fades behind a distant thunderstorm.
A dissipating thunderstorm anvil cloud is seen above pueblo ruins in Wupatki National Monument at sunset.
A dissipating thunderstorm anvil cloud is seen above pueblo ruins in Wupatki National Monument at sunset.

Rainbows

A double rainbow above Cathedral Rock in Sedona.
A double rainbow above Cathedral Rock in Sedona.
A rainbow, dissipating anvil, thunderstorm, and towering cumulus.
A rainbow, dissipating anvil, thunderstorm, and towering cumulus.

Lightning

And lightning…

An amazing anvil bolt...and too close!
An amazing anvil bolt…and too close!
Lightning west of Sedona, Arizona.
Lightning west of Sedona, Arizona.
Anvil bolt over Cathedral Rock. (It's out of focus—<u>you</u> try focusing in the dark!)
Anvil bolt over Cathedral Rock. (It’s out of focus—you try focusing in the dark!)
Lightning illuminates Grand Canyon at night.
Lightning illuminates Grand Canyon at night.
Lightning strikes the Moenkopi Plateau (composite image).
Lightning strikes the Moenkopi Plateau (composite image).
Several bolts strike behind Wukoki Pueblo in Wupatki National Monument.
Several bolts strike behind Wukoki Pueblo in Wupatki National Monument.
The setting sun lights up rain curtains as a brilliant lightning bolt strikes behind Wukoki Pueblo in Wupatki National Monument.
The setting sun lights up rain curtains as a brilliant lightning bolt strikes behind Wukoki Pueblo in Wupatki National Monument.

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.