It has been a dry October and the last measurable precipitation at the Flagstaff airport was September 26 until rain and snow fell on Sunday, October 27.
Forecast models had been showing a slight chance of rain and/or snow with the passage of a cold front but precipitation amounts were light. The GEFS plumes showed generally less than 0.03 inches. The airport actually measured a bit more than that as 0.05″ of rain fell with a trace of snow.
Overall, not a bad forecast. So I was not surprised that rain and some snow arrived with the cold front. I was surprised that it was accompanied by thunder and lightning.
It’s always interesting to observe Thundersnow!
A look at the lightning map shows that the only place where there was cloud-to-ground lightning was in the vicinity of Flagstaff.
It’s been an unusual monsoon season across Arizona this year. After both a wet winter and wet spring—with above normal precipitation amounts all the way into the month of May—things went dry. The North American Monsoon started late this year with the first significant rainfall not arriving until the second half of July. This was unfortunate as the dryness partially contributed to a very damaging wildfire (Museum Fire) burning across portions of the San Francisco Peaks.
Just a few days later, the rains finally arrived. And, then, they stopped again. And it has been that way much of this monsoon season. A few days of rain, then a week or more of dry weather. A normal pattern would have rain falling perhaps four days out of seven for a two-month period. Folks around here have dubbed this monsoon the “nonsoon”.
And, of course, with the lack of moisture and thunderstorms opportunities for photographing storms, heavy rain, lightning, and sunsets has been a challenge. But it only takes one great photograph to make it a successful season. I’m still trying to get that photograph.
Here are some of the more interesting photographs from this “nonsoon monsoon” season.
In celebration of this legacy national park’s centennial, the work of some of the country’s most talented photographers is paired with essays by canyon veteran Scott Thybony in a love letter to an irreplaceable place. Like candles on a birthday cake, 100 breathtaking photographs capture the deep and abiding appeal of Grand Canyon—as Thybony so eloquently writes, its “pure geometry of earth and sky.” This book is truly the “collector’s item” for Grand Canyon National Park’s centennial year!
I’m pleased to note that three of my photographs were selected for inclusion in this book.
The first image is an example of not giving up. I was packing up my gear to leave Lipan Point and drive home when a small cumulus appeared. I stopped what I was doing and watched it for awhile and realized that it might become a thunderstorm. So I unpacked the gear and set it up again and waited. The sun went down and then the storm started to produce lightning. And I got this shot of lightning exiting from the top of the storm, heading down in the clear and then going through a layer of low clouds before hitting and illuminating the ground.
The following two images were shot the same day. Thunderstorms were slow to develop but there was this interesting band of clouds just above the horizon. I waited until the sun was behind the clouds and the result was these beautiful beams of light and shadow spreading across the canyon.
Finally, after the sun had set thunderstorms developed across the North Rim of Grand Canyon. There was still plenty of twilight to backlight the storms and to produced some reflected light in the canyon.
“Leave it as it is. Man cannot improve on it, not a bit. The ages have been at work on it and man can only mar it.”
You cannot see the Grand Canyon in one view, as if it were a changeless spectacle from which a curtain might be lifted, but to see it, you have to toil from month to month through its labyrinths.
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.