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.
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
Cumulonimbus over Hart Prairie.
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.
We left Flagstaff yesterday and spent the night in Albuquerque and today we will drive the rest of the way to Denver. We will be spending two weeks in Denver visiting family and friends—and will do a bit of storm chasing if the right conditions present themselves.
We had dinner last night at the Owl Cafe—a Route 66-style diner. We’ve been here before and like the decor. The food isn’t too bad, either.
The drive from Albuquerque to Denver was interesting as we were in a post-frontal airmass and the clouds had these abstract undulations. We stopped a few times for photos along US 84 in eastern New Mexico.
And so it begins. The North American Monsoon has begun with many thunderstorms but not much rain. As a result, lightning-sparked wildfires are a possibility.
Just by chance, I was heading out towards Mormon Lake this morning to capture images of the building thunderstorms over the San Francisco Peaks. I had noticed that the early buildups had some interesting structure—a combination of convective vertical growth as well as some laminar wave clouds.
As I drove towards Upper Lake Mary I saw a small plume of smoke from a wildfire. Moments later, I spotted a helicopter dropping water on the fire.
Fortunately, the fire was a very short distance from the lake allowing multiple passes in quick succession.
The recent increase in moisture and a slight cooling of temperatures that we’ve experienced over the past few days will result in good chances of quickly containing this wildfire.
The lightning map for 07 July 2018 shows plenty of lightning across the higher terrain—so it’s likely this fire was caused by lightning.