Sunset Convection and Lightning

It was a pleasant evening in Sedona watching thunderstorms as the sun sank lower in the western sky. It was mostly clear in that direction allowing sunlight to illuminate storms in the east. This is one of my favorite setups: clear in the west and stormy in the east.

Early evening sunlight illuminates thunderstorms and Cathedral Rock in Sedona.
Early evening sunlight illuminates thunderstorms and Cathedral Rock in Sedona.
Early evening sunlight illuminates thunderstorms.
Early evening sunlight illuminates thunderstorms.
Lightning from a distant storm after sunset.
Lightning from a distant storm after sunset.
Lightning from a distant storm after sunset.
Lightning from a distant storm after sunset.

The setting sun produced wonderful pastel colors on the clouds and occasionally illuminated the rock spires and buttresses in the middle distance. And after sunset, distant storms showed large anvils along with occasional bolts of lightning.

Lightning and shelf clouds


The past few days have produced interesting storms across northern Arizona.

An isolated thunderstorm develops at sunset.
An isolated thunderstorm develops at sunset.
Lightning illuminates an updraft.
Lightning illuminates an updraft.

An isolated storm developed around sunset and produced both wonderful colors and lightning. Most of the lightning, however, was on the other side of the updraft so the storm instead was lit from the inside like a lightbulb. The storm colors and lightning was nicely reflected in the waters of the Kachina Wetlands.

Low clouds from thunderstorms envelop the San Francisco Peaks.
Low clouds from thunderstorms envelop the San Francisco Peaks.
Outflow boundary and low clouds arrive in Sedona.
Outflow boundary and low clouds arrive in Sedona.
Lightning over the Mogollon Rim.
Lightning over the Mogollon Rim.

A few days later a large line of convective storms moved southwestward across the state and produced a haboob in the lower (and drier) elevations. As the leading edge of the rain-cooled air moved across the San Francisco peaks the clouds quickly enveloped the mountains. About an hour later, the shelf cloud arrived in Sedona and new storms began to develop.

 

Thunderstorms and Lightning

The North American Monsoon has been sputtering—for lack of a better term—the past week or two. We get a few days of storms followed by a hot and dry period. Finally, however, moisture is beginning to increase and we are seeing more storms. I have tried several times this year to get great photographs of storms and lightning but my success rate has been pretty low.

Here are a few photographs from the past week.

Clouds develop across the whole sky in Sedona.
Clouds develop across the whole sky in Sedona.
An outflow boundary arrives and thunderstorms develop within a few minutes.
An outflow boundary arrives and thunderstorms develop within a few minutes.
A distant thunderstorm seen from Wupatki National Monument.
A distant thunderstorm seen from Wupatki National Monument.
Mid-afternoon lightning near Mormon Lake.
Mid-afternoon lightning near Mormon Lake.

And, finally we have a time lapse of the same storm that produced the lightning above. The video is 200x real time; from the motion it can be seen that the storm has some slow rotation. This storm moved off the higher terrain and became severe as it neared the Camp Verde area.

The weather models have been consistent with forecasting a significant increase in storm activity next week.

Thundersnow!

Thundersnow. Just the sound of it is exciting—snow accompanied by thunder and lightning. Although it is fairly rare east of the Rocky Mountains it is a bit more common across the west.

And we had multiple rounds of thunderstorms producing snow yesterday (Saturday, 13 February 2021) in Flagstaff. It was pretty amazing to see heavy snow falling and then a sudden flash of lightning followed by the muffled sound of thunder a few seconds later.

Radar depiction of precipitation across northern Arizona at 1:51 P.M. on 13 February 2021. Note the small lightning symbols near Flagstaff showing locations of cloud-to-ground lightning.
Radar depiction of precipitation across northern Arizona at 1:51 P.M. on 13 February 2021. Note the small lightning symbols near Flagstaff showing locations of cloud-to-ground lightning.

There were several clusters of thunderstorms that moved across the area during the afternoon. None of these were recorded by the ASOS at KFLG—and it’s not obvious why they were missed. The ASOS certainly captured the start of snow and then the moderate (SN) and heavy snow (+SN). Perhaps the lightning was just far enough away to not register.

KFLG 132307Z VRB06G25KT M1/4SM +SN FZFG VV004 M01/M02 A2960 RMK AO2 P0006 T10111017
KFLG 132257Z 29009G27KT 260V340 1/4SM SN FZFG VV005 M01/M01 A2961 RMK AO2 PK WND 24031/2239 SLP027 P0007 T10061011
KFLG 132243Z 27012G31KT 1/4SM SN FG BKN008 OVC029 00/M01 A2959 RMK AO2 PK WND 24031/2239 P0004 T00001006

Here is a loop of the visible channel from the GOES-17 satellite. Superimposed on the clouds are color blobs showing Group Flash Count Density from the satellite lightning mapper. The next image shows lighting from surface-based lightning detectors and shows numerous cloud-to-ground strikes across northern Arizona.

 

Locations of cloud-to-ground lightning across northern Arizona on the afternoon of 13 February 2021.
Locations of cloud-to-ground lightning across northern Arizona on the afternoon of 13 February 2021.

Model-generated soundings from the HRRR showed that there was very slight convective instability with surface-based CAPE values of around 100 J/kg.

Model-derived sounding for Flagstaff at 20 UTC 13 February 2021 (1300 MST)
Model-derived sounding for Flagstaff at 20 UTC 13 February 2021 (1300 MST)

That is a shallow layer of instability and very weak instability—but was enough to generate thundersnow.