The Cerulean Arc

I chased some stunning high-based storms with brief supercell structure in southern Arizona earlier this week.

A trough moving in from California was forecast to take on a negative tilt as it drifted into Arizona. Dynamics would be favorable for severe storms with 40-50 kts of shear, positive vorticity around the base of the trough, and some chances for winds sufficiently veering with height to support multicell and weak supercell structure. The SPC forecaster commented that the NAM was handling parameters nicely, so I gave it more attention for my initial plan than the RUC and GFS. It forecast a tongue of modest instability (500-750 j/kg MLCAPE) moving eastward from Yuma through the central deserts and then lava-lamping a blob of CAPE northward through the Phoenix area by late afternoon/evening.

I was initially tempted to head west, toward Kingman that morning. Ongoing convection associated with another field of instability was being spurred by a streak of upper air support. It didn't help that Flagstaff NWS was discussing the remote possibility of an isolated tornado for the northern Arizona forecast area. The Phoenix forecast for southern Arizona conceded the possibility of brief supercell structures, but didn't go so far as to leave the tornado possibility on the table. Still, the best combination of instability and jet streak dynamics seemed poised to effect southern Arizona more favorably than elsewhere. I also wanted to play in some terrain that had better visibility. So that's where I headed. I planned my first stop for Wickenberg to sidle closer to the front and then have a good road option to the southeast as I watched how convection developed.

By 10:30AM as I was nearing Cordes Junction I could see storms already blossoming south of Wickenburg along the cold front. I chastised myself for getting a late start and possibly missing an early show. But better dynamics were still hours away, so I pushed the frustration aside. As I approached Wickenburg along Rt. 74, a gap in the hills allowed a brief birds-eye view of one of the early storms pushing out an arcing ring of dust--one of many I'd get to sample through the day.

Storms erupting southwest of Wickenburg.

As I sat at the intersection of Rt. 74 and 60 checking radar and satellite, I was dodging ongoing feelings of self-doubt. Convection in northwest Arizona was doing very well for so early in the day while storms popping up in southwest Arizona were blooming and dying in short order, shooting thin anvils eastward in spurts. I was starting to worry that the atmosphere was going to get tapped of whatever available moisture there was, and the show in the north might be the only real play for the day. Still, I decided that as long as I was part-way there, I might as well commit the rest of the way to my southern target. So I cruised the rest of the way past Laveen, and south of South Mountain. Along the way, the storms pulsing along the cold front were really starting to push the dirt around. Much of my drive south ran me right through the diffuse wall of a dusty gust front.

Driving along the dusty gust front south of Laveen, AZ.

I parked the car off the road in the scrubby wastes northeast of Estrella Mountain (appears to be a perfect spot for disposing of contraband and bodies) and watched the merging arcs of dust pushed westward. A strong storm peeling away from Ajo dissipated as it approached and ran into a sad capping problem that was centered pretty much over my head. I held onto hope that the cap would erode as the dust cleared out and the surface heated back up. But the surrounding environment continued to be harsh on convection. One sad little cell pushed up over the mountain, but then faded into a mist.

Dying storm pushes another arc of dust eastward as it drifts over Estrella Mountain.

A weak cell makes it over the ridge and manages to develop a tiny little base.

The same cell now fades into a hazy mist.

Another batch of convection brewed back up over Ajo and then split as it moved over Interstate 8. The right mover looked really good, and I quickly headed south toward Maricopa to intercept it. As I rounded the east side of Estrella Mountain, I could see the dark core of the storm pushing up against the ridge. I soon caught a glimpse of the rain free base and a distinct lowering. Maricopa Road was thick with 75 mph rush-hour traffic, and I had a challenge finding a place to pull off safely. Casa Blanca Rd. did the trick. Although the storm had dwindled to a fraction of its former bulk, it still had a very nice show to put on. I spent the next several minutes photographing and filming a beautiful wall cloud being sculpted out of the storm's base.

Persistent lowering beneath the rain free base.

Panorama of storm and surroundings as wall cloud takes shape.

RFD begins to sculpt the wall cloud.

Closer view of wall cloud.

Wall cloud tries to pull in a little bob-tail on the right edge, while beginning to recede back into the base. RFD is cascading nicely down the left/south side.

After dropping into a nice, morphing cylinder, with a bit of RFD cascading down its south edge, it merged back into the base for a few minutes. As the storm moved further north, the base tightened up into a stunning barber pole with another, furry wall trying to form beneath.

The base of the storm tightens back up, developing barber pole structure.

By this time, another cell to my south started raining on me and feeding my target storm some cool, misty air. As I rushed northward to to get out of the rain, the storm base began to erode into a tattered claw, painted across a dusty, desert landscape. I hated not having a good place to pull over and capture the amazing sight to my left. To make the best of it, I rolled down the window, and snapped several uncomposed shots while concentrating on the road ahead of me, hoping one or two of them would frame it nicely. Fortunately that worked, and I came away with a couple in that series that I actually liked.

Panorama of storm base and surroundings as another storm to the south begins to rain on the parade.

The swirling storm base begins to tatter and erode as it chews on more stable inflow.

Last hurrah before traffic, stop lights, and curtains of rain let it pull away into Chandler, Mesa and points beyond. Note the stubby little tail hiding in the rags.

Before leaving that morning, I tried to sober myself with some rough odds:

• 80% chance of seeing some storms.
• 30% chance of getting a good look at a severe or otherwise interesting storm
• 10% chance of intercepting a storm with supercell structure
• 5% chance of a wall cloud
• <1% chance of seeing a funnel or better

Four out of five's not bad, I figure! I was pretty happy with how things went as I spent the next 160 miles driving back up the mountain in pouring rain. Although the Maricopa storm possessed some key elements, I'm not sure I would call it a supercell--maybe a 'marginal' or 'brief' supercell. After reviewing the time lapse video, it did show rotation in the updraft, but it was not vigorous and had a very small radar signature by the time I intercepted it. In hindsight, I think that outflow from the earlier convection was what was killing the storms that I hoped would "come to me". I should have taken the extra driving hit and headed further south to Interstate 8 to catch a more pure fetch of moist southerly air where the convection was happier.

Taking a queue from Skip Talbot--

Lessons Learned

• Don't let the early show distract you from the main play for the day.
• Do factor in the atmospheric consequences of the early show when positioning for the main play.
• Clean dust off my camera's sensor--cleaning the blobs out of the images later is a pain in the rear.
• Southern Arizona has better chase terrain and visibility than the mountains of northern Arizona...but the road network still stinks compared to the plains.
• Invest in a swatch of black velvet for the dashboard. Positioning the video camera on a huge, dark jacket to hide dashboard-window reflections is an obnoxious balancing act.
• Blindly shooting photos out the side window can actually work if you have no other options.
• Even at low speed, cruise control on my car is a force of evil when it encounters flooded highway ruts.
• September/October in Arizona is my new second-chance chase season.

The second week of September has been a great week for organized storms in Arizona. A cutoff low developed over southern California, and has been drawing up moisture for several days and providing decent shear aloft. Lower level winds haven't been very strong and veering with height in the first kilometer not very promising. However, bulk shear from 30-40 knots, cooling and diffluence aloft, and ample moisture led to strong storms and support for occasional supercells.

Supercell thunderstorms are not common in Arizona, but after missing the storms that led to last year's Arizona tornado outbreak, I've been keeping an eye out for California cutoff lows. Being at the right place at the right time to view and film a rare Arizona tornado is so close to being unrealistic, that I'm not too anxious about it. However, catching an Arizona supercell seemed doable and would be a very nice gem to collect.

I've had my cameras ready in the car and kept an eye on radar in hopes of catching a good storm. I made a couple local chases the week before, caught some broad rotation in one storm and brief barber pole structure in another, but not much else. Then on the afternoon of September 13, I noticed weak, but sustained, rotation on a couple storms on doppler radar. I headed outside to get a look and to the north I saw a robust storm perched over the San Francisco Peaks. The rain free base sported a zone of rising scud, and I was surprised to see what appeared to be a wet RFD slot slicing into it. As the razor edged rain band pushed in, the rising scud quickly congealed into a wall cloud with a laminar profile and nice rising motion. All I had was my cell phone, so I had to suffice with a couple low-quality photos.

RFD and brief wall cloud southwest of San Francisco Peaks about 2:30 PM

Move mouse over image to view labels. Click for larger version.

RFD and wall cloud progressing

Hoping it would hold together, I quickly ran to my car to grab my cameras. By the time I got back to a good clearing in the trees, the original updraft cycle had eased off and the wall cloud had broken up. I was pretty disappointed, but the storm still looked strong, so I found a new vantage point along a stairway leading to the roof of my office building. I set the video camera up for a time lapse while shooting still photos as the storm cycled two more times.

Storm base moving over Schultz Pass

Panorama showing storm structure 3:00 PM

Move mouse over image to view labels. Click for larger version.

While shooting photos, I called my wife while she was running errands about a mile further north, closer to the rain free base. Besides describing a wicked looking storm and an occasional spray of hail, she mentioned the warm inflow that was feeding it.

The videos below show a time lapse view of the storm. I suggest clicking through to Youtube and viewing in high res

By now, a flanking line and gust front had developed along the storms southwest flank, and there appeared to be an inflow tail stretching eastward behind Mt. Elden. One area of rotation drifted eastward through Shultz Pass and dropped a broad, tattered wall cloud. This area seemed to be occluding while new circulation was trying to develop just south of it on the other side of the RFD gust front.

This second video shows detail in the wall cloud, including an interesting, conical structure drifting through it. The structure persisted for about 40 seconds. Although I wonder if it was an embedded funnel, I can't be sure--I can't discern motion in the dark silhouette.

Wall cloud drifting behind Mt. Elden.

Suspected funnel embedded in wall cloud.

Move mouse over image to view labels. Click for larger version.

Storm structure as new base forms.

The new area of rotation began to pull in rising scud and even started to form a tail cloud. It was definitely exciting to see it try to tighten up as rotation got faster, but it lost cohesion, and the storm pulled away to the northeast and out of view over the mountain.

RFD gust front makes a strong push.

Tail cloud begins to feed into new lowering.

RFD Slot.

This cycling supercell was a real treat to view. While I imagine it would be a disappointment by plains standards, it was pretty awesome as Arizona storms go. Unfortunately, the core was planted right over the Schultz Fire burn area and led to another round of serious flooding for neighborhoods downstream.

The station that recorded the radar images below is located to the southeast.

Base velocity at 2:30 PM showing 15 kt gate-to-gate shear during first wall cloud photos.

Base velocity at 3:00 PM showing 20 kt gate-to-gate shear in two locations during next sequence of photos.

Base reflectivity at 3:00 PM.

I got on the road Saturday afternoon, left Flagstaff, drove most of the night, and made it to eastern Nebraska by Sunday late afternoon.

I'll try to do a more detailed summary later with more photos. (I'm extremely worn out.)

After checking models and spc discussion each time I stopped to fuel up, I decided I would head to the warm front. Unfortunately, eastern Nebraska turned out to be a wasteland of uncooperative cloud streets. The cap wasn't budging there at all. I figured I was going to have a complete bust on my first day out. But then inhibition started to part in South Dakota, a few storms started to blossom. Most were too far to consider, but a small, fresh one was within reach, so I raced north. As I got closer, I realized the cap had clamped down and nothing was left but an orphan anvil.

I kept going north, just in case, and was suprised by a view of a new tower going up on the other side of the Missouri river, half-lit by the coppery light of the setting sun.

The new tower was farther north than I thought, and was moving north at about 25 knots. I decided not to keep chasing it in the dark, so I broke off, satisfied to see it sputter with lightning as it drifted away. At least I got a distant storm and some lightning for day 1.

I fueled up again and did some supply shopping. Afterward, as I drove to a section of gravel roads south of Mitchell, SD to park for the night, I was overwhelmed by nonstop lightning behind me. I pulled over to figure out where it was coming from. Sprawled out to my west was a huge, sculpted shelf cloud, gaping with rain, wind and lightning--and it was visibly expanding in my direction. I didn't want to get the car golf-balled, so I raced down the dirt roads, going after a good north-south paved road. Along the way, I made some brief stops to photograph this majestic thing.

At one stop alongside a small lake, the sound of katydids, frogs and other nocturnal creatures blended in with the non-stop thunder of the approaching storm. It was wonderful. As I continued south and east, I realized the entire gust front was going to chase me into Missouri if I let it. So I hunkered down in a farm field access and embraced the drenching rain and unceasing lightning. It was an amazing way to end the day.

An active and horrific weather pattern laid siege to much of the eastern US this past April, while the bulk of the central plains remained untouched. May is here now, and it looks like the first round of activity for the plains is shaping up for early next week. Models are generally showing that an upper low will dig in across the western US while low level moisture surges northward across the plains and the midwest. At 4-6 days out, position of upper level support relative to surface boundaries and moisture is difficult to pin down, but severe weather seems likely at points across the plains during this period.

I'm planning to pack up and head east on I-40 Saturday afternoon or Sunday morning, depending on whether conditions Sunday afternoon look favorable for severe storms along the dryline. From there, we'll see how things shape up from Texas through Nebraska. I'm not sure that I want to get drawn as far northeast as Iowa, but if the setup looks really good...

What a strange weather day. I was aware of the potential for severe weather today, but since it was a work day I didn't give it too much thought the night before.

Then I awoke to the sounds of the emergency broadcast system issuing a tornado warning on the TV in the living room (where Harrison was enjoying some early morning cartoons).

I turned on the computer, pulled up local radar and saw a train of red tornado warning polygons piling up and following a line of storms just west of Flagstaff. So yeah, it was a work day, but 10 miles from town? I'd be a mess if I didn't at least try. I asked to take a few hours off at the office, and then headed west on I-40 to Bellemont.

I had no overall plan, it was spur of the moment, and I hadn't spent any time going over the synoptic situation or models. No mobile data either. I just figured, one tornado-warned storm after another was cooking northward and ending up between Bellemont and Flagstaff...I'd surely see at LEAST some interesting structure.

Wrong.

No understanding of the overall setup, no data, towering ponderosas packed against 90% of any given roadway, very low cloud bases, storms moving at 40 mph, and a sparse road network that forces you to commit with no options for fine-tuned adjustment made for endless frustration.

I spent most of the time in drenching rain and pea-sized hail or looking up at racing clouds from inside a canyon of trees. As I cruised along I-40, one cooperative gap in the trees gave me about a 3 second glimpse of a nicely flared rain free base on a storm that had been tornado-warned near Sedona. I wasn't able to re-acquire it. Just too much terrain. Hindsight: I should have worked south on I-17...once the storms started training eastward they lost their punch after moving north over the rim.

The Bellemont truck stop is situated in a nice, open prairie landscape, which provides a better visual if that's where a mesocyclone plans to traipse. Which, none did while I was sitting there without radar data.

If I had been there several hours earlier, it would have been a completely different situation. Severe storms are fascinating, but not when lives and livelihoods are threatened. One confirmed tornado, and likely some serious straight-line winds were unloaded and wreaked havoc with this little community between 6:00 and 7:30 this morning. As I drove around looking for an open vantage point to watch the incoming storms, DPS was everywhere. Several rail cars were laying on their sides, demolished semi frames were in the median of I-40, buildings had their roofs and siding peeled away, and an RV lot looked like gravity had suddenly shifted, toppling and bursting random campers open. Fortunately, there were no fatalities; however seven were injured.

So, yeah, I was frustrated by how the chase went, but how can that even compare to the frustration of having your home ravaged, pieces of your life blown off into the mountains, or someone you love having glass and debris picked out of them in the ER?

Anyway, a very strange weather day. See below for some photos.

Last month while running an errand for work, I noticed a thin funnel hanging below a developing storm base. Of course I didn't have my camera with me, but I did have my cell phone. I finally remembered it was hanging out on my phone today, so here is the photo.

Shear funnel. Flagstaff, AZ. August 16, 2010

Click here for a 3 frame animation.

Next month, we'll be doing some rock hounding in Iron County, Utah. When we were there last year, we spent just a couple hours at some mine dumps west of Cedar City and found some great specimens...several of these turned out to be fluorescent under a standard black light (long wave UV). Since I really want to track down some more of these awesome rocks, I ordered a couple portable UV lamps to bring with us. The first one arrived a few days ago--a 4 watt short wave UV lamp. I hadn't seen any of our collection under short wave UV yet, so I got busy shining it on everything we had. I was excited to see that this lamp nearly doubled the number of fluorescents we have--and some of them are stunning!

A four watt lamp is very low power, but it's enough to examine things (and was all I could afford for the time being). I won't be able to stalk around after dark and shine it on a massive hill of mine tailings and see anything, but it works well enough that I should be able to throw a black tarp over myself and get in close to see if anything lights up.

Here are the photos of our current fluorescent collection. It contains rocks from the Comstock Mine Dump, Iron County, UT; Chalcedony from Brian Head, UT; Rocks from north of La Madera, NM; Petrified Wood from Hurricane Mesa, UT; and some small, bright red specimens from south of Cleator, AZ. Click to view larger versions of the images (the larger ones are better).

Click this link to view large rollover graphic showing all 3 images aligned (550K).

White Light

Long Wave Ultraviolet

Short Wave Ultraviolet

It's been a busy weekend for the hotshots around Flagstaff.

Schultz Fire - June 20, 2010

This one gave me a fright when I opened the kitchen window on the north side of our house this afternoon. For a couple seconds I thought that our summer monsoon had gotten a very unexpected start, but then I noticed the yellow and brown coloration and gasped at how close and large it was. The updraft was strong enough that it was pushing up a hedge of white pyrocumulus along the roiling top of the smoke column. Rather than clog up Highway 89 any further, we headed east along old Rt. 66 to get a vantage point near the Walnut Canyon overpass. We pulled of the road and watched the slurry bombers and helicopters drifted across the angry wall of smoke. I spent a few minutes shooting a time lapse of the breathing cloud of blue and brown smoke. Be sure to click the images for larger versions.

Schultz Fire erupts behind our house.

Schultz Fire Panorama from Rt. 66.

Close view of the base of the Schultz Fire.

Time lapse of the Schultz Fire. Select the 480px size for the best quality.

Hardy Fire - June 19, 2010

This one started yesterday, Saturday June 19, on the south side of town where it forced the evacuation of Little America Hotel and a few surrounding homes. I first noticed some white whisps of smoke shortly after lunchtime and within a couple hours it was shooting up a fierce smoke column. I drove to one of our office locations on 4th street to get some photos of the air tankers and helicopters orbiting the blaze. Click images for large versions.

Air tanker crosses the Hardy Fire.

Close view of Hardy Fire air tanker.

Wildfire copter maneuvers around the Hardy Fire.

Taking a Great Plains storm chase trip is something I've wanted to do for a long time. For the past couple years, I've been learning and practicing severe weather forecasting, and running some real-time virtual chases, but nothing can compare to getting on the road and actually doing it. So as May approached, I started keeping my eyes peeled for a good weekend setup.

Over the weekend of May 15/16, I noticed conditions favorable for severe weather might be shaping up for the following weekend, May 22/23. Low pressure was forecast to set up over the western US and spend several days sending impulses along very moist air across the central US. Upper air support, speed and directional shear all looked like they would provide support for tornadic supercells in varying locations.

As the week progressed, the GFS and eventually NAM forecast models continued to confirm this set-up, while timing and locations fluctuated from day to day. I got the o.k. to take Friday and Monday as vacation days, and planned to head for the Colorado/Wyoming/Nebraska borders on Friday, South Dakota/Nebraska on Saturday, and somewhere along the dryline from Nebraska to Oklahoma on Sunday. To get the best chance for current data on the road, I activated wireless broadband access with Verizon and got my forecast, satellite and radar links set up on the MacBook.

Giselle said she would like to join me, and the two of us took off Thursday night for what turned out to be a fantastic road trip. She ran the laptop and shot video so I could drive and snag photos.

Click the links below for photos, video and details from each day:

• 
  May 21 - Lingle-Lusk, Wyoming - Funnel Cloud, quarter-sized hail
• 
  May 22 - Bowdle, South Dakota - 3 Tornadoes cycling from a single, intense mesocyclone
• 
  May 23 - McDonald, Kansas - Marble-sized hail and nighttime tornado-warned supercell light show
• 
  May 24 - Goodland, Kansas - Quarter-sized hail and mid-level shear funnel

Chase Vacation Reports

• Chase Vacation Summary
• Chase Day 1 - Lingle-Lusk, Wyoming
• Chase Day 2 - Bowdle, South Dakota
• Chase Day 3 - Northwest Kansas
• Chase Day 4 - Goodland, Kansas

On Thursday night, May 20, we took I-40 from Flagstaff to Albuquerque and then headed north on I-25. We grabbed sleep at rest stops and off ramps along the way. By noon, we were bogged down in traffic in the heart of Denver (what a mess). I figure we lost about an hour trying to pierce the heart of the city instead of taking one of the outside routes.

North of the city, we had a bite to eat at Wendy's while strongly sheared cumulus tried to pierce the CAP along the front range. The tough part was trying to decide where initiation would take off. Decent CAPE, shear, and a frontal boundary were setting up in southeast Wyoming, so we got back on I-25 and headed north. As we approached Cheyenne, Wyoming, radar showed cells getting healthy along I-25, further north near Wheatland. One cell pulled its act together and started peeling away to the east-northeast. In an attempt to parallel and get ahead from the south, we broke northeast on Hwy 85 toward Torrington and Lingle.

As we approached Torrington, the supercell dominated the sky to the north like a great hen roosting over her clutch with features gradually resolving along the base.

As we entered Torrington and headed toward Lingle on US-85, trees and buildings demolished our view, however, upon clearing some trees about 00Z, we got a sudden and stunning view of a wall cloud and what appeared to be a funnel silhouetted to the northwest. When in silhouette, it's not possible to determine rotation, so at the time, all we could do was film it and see if we could catch up.

Video frame grabs:

The SPC report later confirmed two tornado touchdowns northwest of Lingle at 23:55Z and 00:01Z. So I'm confident that the feature we saw was indeed a funnel--whether it was a tornado at the time we saw and filmed it, I couldn't say.

We took US-85 north of Lingle, and caught fractured glimpses of the disintegrating wall cloud between otherwise stunning, hilly terrain. When we finally caught up to it, the wall cloud was gone, although the base was still slowly rotating. A deep, turquoise light emerged from within.

Road options were seriously limited, so we couldn't follow this one as it tracked to the northeast. So we continued north on US-85 as other storms erupted.

North of Lusk on US-85, we drove beneath an enormous, beautifully lit shelf cloud.

Click to view panorama (Quicktime required).

This time lapse video shows motion of the shelf cloud and lowered inflow base:

Illumination beneath this storm was surreal and bathed the Wyoming landscape with a dream-like light.

After nightfall, we spent some time in Lusk, looking for a good place to stay the night and getting pelted with nickel and some quarter sized hail. Every room in Lusk was taken, so we drove on to Chadron, Nebraska and tried to rest up for our next day in South Dakota.

SPC Report for May 21, 2010

Chase Vacation Reports

• Chase Vacation Summary
• Chase Day 1 - Lingle-Lusk, Wyoming
• Chase Day 2 - Bowdle, South Dakota
• Chase Day 3 - Northwest Kansas
• Chase Day 4 - Goodland, Kansas