Beautiful Sunset Followed by Snow

A strong storm system approached the southwest yesterday and moved through the state overnight. Ahead of the storm, clouds began to increase just before sunset and I found myself at the Mormon Lake overlook. The cumulus clouds were fairly shallow so that the sunlight hitting the tops of the clouds was scattered downward and provided some diffuse lighting and color to the cloud bases.

The setting sun faintly illuminates the meadows of Mormon Lake and provides some color to the field of cumulus clouds.
The setting sun faintly illuminates the meadows of Mormon Lake and provides some color to the field of cumulus clouds.
A few minutes later and the sun is now illuminating the bases of the clouds.
A few minutes later and the sun is now illuminating the bases of the clouds.

There was also a thin gap between the clouds and the ground allowing for just a few minutes of direct sunlight.

Here are a few photographs of the sunset and clouds along with some sunlight spilling across the currently dry lakebed of Mormon Lake.

Band of showers and thunderstorms associated with the advancing cold front.
Band of showers and thunderstorms associated with the advancing cold front.

As the storm and cold front approached showers and thunderstorms quickly developed with a line of strong thunderstorms developing about an hour after sunset. There was quite a bit of lightning as the line of storms moved across the area. The sound of rain faded as it was replaced by snow falling in the wake of the front.

New-fallen snow lies on this cinquefoil plant.
New-fallen snow lies on this cinquefoil plant.

In the morning there was snow covering the ground. Measurements were difficult as strong winds during the night had blown the snow such that some areas had a few inches and other areas were bare.

The snow juxtaposed with autumn colors was very pretty but my favorite photograph was the snow on this cinquefoil that still has some flowers.

Late September Storms in Flagstaff and Sedona

Late September provided a chance to photograph storms associated with the passage of an upper-level trough crossing the southwest. Ahead of the trough would be moderate-to-strong upper level winds along with deep-layer shear. So there was a possibility of a few strong thunderstorms that might develop supercellular characteristics. As well, there would likely be a line of storms that formed on the surface cold front pushing southeastward across the state.

Shelf cloud associated with an outflow boundary from a cluster of thunderstorms moving over the San Francisco Peaks.
Shelf cloud associated with an outflow boundary from a cluster of thunderstorms moving over the San Francisco Peaks.

The plan was to head north to Cameron, Arizona, then slowly work back to the south as the line of storms moved across the area. I went to Cameron but the storms to the west and northwest were already weakening while storms farther to the southwest were strengthening. So — back south I went with stops at Wupatki NM and Sunset Crater NM while watching the storms. A cluster of storms developed north of the San Francisco Peaks and eventually pushed a strong outflow across the mountains. The leading edge of this outflow had an interesting cloud structure and was briefly very photogenic.

Sunset colors on the clouds at Fort Tuthill County Park.
Sunset colors on the clouds at Fort Tuthill County Park.

After a few photos, I continued moving across Flagstaff on my way home. Suddenly, the sun dropped low enough to get below the clouds and for a few minutes there was great sunset light on the bottom of the clouds. I shot a few photos at Fort Tuthill County Park with the undersides of the clouds full of sunset colors. And, then just a few minutes later it was over and the light was gone.

So I could have just stayed at home and gone out shooting at the last minute of daylight.

Late afternoon sun lights up a distant thunderstorm and the Red Rocks of Sedona.
Late afternoon sun lights up a distant thunderstorm and the Red Rocks of Sedona.
The setting sun and crepuscular rays.
The setting sun and crepuscular rays.

The next day showed potential for a few interesting storms south of Flagstaff. I headed to Sedona and spent a few hours photographing storms.

The setting sun with crepuscalur rays was pretty nice.

Edit: corrected typo in photo caption.

 

Thunderstorms and Tornadoes in Arizona

A potent weather system moved across Arizona on Tuesday, October 5, 2021, and produced a variety of weather including tornadoes, large hail, heavy rain, and flooding. This system was well forecasted and the various models did a very good job depicting the possibilities.

Radar-estimated rainfall amounts across Arizona on Tuesday morning.
Radar-estimated rainfall amounts across Arizona on Tuesday morning.

Areas of moderate rain moved across Arizona in the pre-dawn hours with many locations receiving more and one inch of rain by sunrise.

There had been some expectations that the severe weather would commence before sunrise owing to the favorable vertical wind profiles. Both the low-level shear and deep-layer shear supported organized thunderstorms with the possibilities of rotating supercells and even tornadoes. That scenario did not manifest probably because the widespread overnight rain cooled the boundary layer enough to inhibit strong thunderstorm development

The forecast models also suggested a second period of severe weather was possible in the afternoon as temperatures warmed and buoyant instability increased across the area.

Severe thunderstorm with a Three-Body Scatter Signature (TBSS; also known as a "hail spike").
Severe thunderstorm with a Three-Body Scatter Signature (TBSS; also known as a “hail spike”).
Severe thunderstorm with a hook echo (left) and strong velocity couplet (right). The box indicates that a Severe Thunderstorm Warning is in effect for this storm.
Severe thunderstorm with a hook echo (left) and strong velocity couplet (right). The box indicates that a Severe Thunderstorm Warning is in effect for this storm.
Severe thunderstorm continues to show a hook echo (left); on the right is Correlation Coefficient where low values may indicate tornadic debris. The warning has been upgraded to a Tornado Warning.
Severe thunderstorm continues to show a hook echo (left); on the right is Correlation Coefficient where low values may indicate tornadic debris. The warning has been upgraded to a Tornado Warning.

Strong thunderstorms developed across the desert regions of central and southern Arizona in the afternoon. These moved quickly to the northeast and into the higher terrain of the Mogollon Rim and Tonto Rim. At least two of these thunderstorms began to acquire supercellular characteristics and began to show rotation signatures in the Dopper radar data. By mid afternoon, one storm had developed a well-defined hook echo and velocity couplet. This storm was already producing strong winds and hail and a Severe Thunderstorm Warning (SVR) was already in effect. As the rotation rapidly intensified, the SVR was replaced with a Tornado Warning (TOR). Polarimetric Dopper radar data indicated low values of Correlation Coefficient (CC). This often accompanies tornadic debris lofted into the air. This was clearly a dangerous storm and the TOR was justified.

Multi-Radar Multi-Sensor (MRMS) depiction of large hail swaths.
Multi-Radar Multi-Sensor (MRMS) depiction of large hail swaths.
MRMS rotation tracks associated with the tornado.
MRMS rotation tracks associated with the tornado.

Eventually, the rotation weakened but the storm was still producing large hail as it moved northeastwards. Other storms also produced large hail. The Multiple Radar Multiple Sensors (MRMS) data shows these long swaths of large hail across portions of Arizona.

Forecasters from the National Weather Service offices in Arizona did a great job of anticipating this severe weather event and issuing timely warnings.

Lightning and Rainbows

Twilight lightning over Kendrick Park. The north flanks of Kendrick Peak are illuminated by the bolt.


We are in the midst of the “Transition Season” where the summer monsoon pattern fades away and the mid-latitude westerlies and low pressure systems move across the area. Another of these events is in progress as a weak closed-low moves across the southwest bringing showers and thunderstorms to the area.

Thunderstorms begin to develop over the San Francisco Peaks.
Thunderstorms begin to develop over the San Francisco Peaks.

Saturday afternoon we set out for the north side of the San Francisco Peaks hoping that thunderstorms would form over the higher terrain and then move northwestward across Kendrick Park. A few storms did form over the peaks and some of them were briefly photogenic but there was very little in the way of lightning. Eventually, approaching rain chased us from Kendrick Park to the northwest where we set up near Slate Mountain in a large meadow with good views of the peaks.

Distant lightning under the rainbow.
Distant lightning under the rainbow.
A multi-pronged lightning strike under the rainbow.
A multi-pronged lightning strike under the rainbow.
Twilight lightning over Kendrick Park.
Twilight lightning over Kendrick Park.
Twilight lightning over Kendrick Park. The north flanks of Kendrick Peak are illuminated by the bolt.
Twilight lightning over Kendrick Park. The north flanks of Kendrick Peak are illuminated by the bolt.
Twilight lightning over Kendrick Park. The north flanks of Kendrick Peak are illuminated by the bolt.
Twilight lightning over Kendrick Park. The north flanks of Kendrick Peak are illuminated by the bolt.

These slow-moving storms continued to move towards the northwest and this time we got lightning and rainbows—and rainbows with lightning. As the sun dropped lower in the west the rainbow quickly faded and rain was again approaching our location. We retreated back to Kendrick Park—this time with the thunderstorms located to our northwest with light from the setting sun still illuminating some clouds. Lightning stikes were frequent and close enough to fill the field of view of the 17-mm focal length lens. Several of these lightning bolts struck the northern flanks of Kendrick Peak. About a half-hour after sunset it was over and the storms quickly dissipated.

Another fun day of storms and lightning.

250-mb height/winds at 0000 UTC 26 September 2021.
250-mb height/winds at 0000 UTC 26 September 2021.
24-hour lightning plot with a lightning cluster near the San Francisco Peaks.
24-hour lightning plot with a lightning cluster near the San Francisco Peaks.