Beautiful Outflow, Day 3: Along a Familiar Trace

August 21, 2011 by · Comments Off on Beautiful Outflow, Day 3: Along a Familiar Trace
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Limon to Sheridan Lake CO (again!)
18 June 11

SHORT: Observed high-based, outflow-dominant supercell with “cheezenado” near Kit Carson CO and deeply textured spectacle of structure. Pretty sunset near ITR.

LONG: This was the third straight day of outstanding outflow in the American Outback. We started the day in LAA, with a stop at Bent’s Fort along the way to our target area, which remained the LIC-PUB corridor as supposed the previous night. While the Fort was fun to visit and photograph again, we slept in too long, got there later than hoped (midday), and stayed long enough to miss the initiation and early stages of a supercell near LIC.

Roaring N out of Rocky Ford, we caught up to the thrice tornado-warned storm just S of LIC (it was, fortunately, rather slow moving up to that point). Despite its fine appearance on radar reflectivity for over an hour prior, early visuals suggested nothing even close to tornadic: a high based storm with a rather small, tilted updraft and opaque to translucent core. The temperature in that RFD was 56 deg F, not exactly priming the pump for tornado action given the lofty LCL of the storm.

We took a little bit of mainly sub-severe hail, from the trailing (rear-flank) precip area while turning around to jog S and E toward Hugo. A major core-dump just N of Hugo (as seen looking NE from just W of town) sent the storm on a southeastward, outflow-surfing odyssey that seemed quite familiar. Already, the irony wasn’t lost: the storm of interest was in the same general area, also high-based and apparently outflow-dominant, and headed roughly the same direction, as the supercell the afternoon before. Indeed, we would retrace much of the previous day’s familiar path.

One difference this day was that the storm legitimately threatened to produce something tornadic on two occasions–both when my phone’s signal-bar area was stamped “No Service.” [Thanks again, AT&T with your disingenuous “97% of the population” advertising.]

We pulled off US-287 near Wild Horse and drove a few miles up a dirt road for a better view, only to see that the terrain constantly was higher between us and the storm. As we got closer, a lowering I had seen for a few minutes in the distance became visible as a persistent, smooth, bowl-shaped (and sometimes fat-cone shaped) protuberance embedded in translucent rain. It was rotating–not very fast, but noticeably. As I got out to take this wide-angle shot, the lowering’s bottom became more rounded and higher, and it went away within a minute. I was imagining what a supercell like this could do with less outflow, lower cloud base and more inflow-layer moisture.

Meanwhile the already-nice structure just kept getting more and more textured and beautiful (looking NW from near Kit Carson). The sharply defined, undular raggedness of the bottom of each cloud-base terrace gave me the impression of looking upward from beneath at a boiling liquid surface.

::::: Begin meteorological interpretation :::::
In a way, though the causative processes are much different, the convective principle is quite similar, when you consider the “liquid surface” analogy as a reverse counterpart of the CCL or LCL. In boiling water, the liqud turns to vapor. At the cloud’s LCL or CCL, the vapor condenses to droplets. Amidst a very broadly intense updraft, little bitty parcels neighboring each other are reaching their condensation pressure fast, but at slightly different elevations, giving the underside of the cloud mass such a rough, sandpaper-like appearance. The difference in condensation level from any one of the “mini-parcels” to another probably is related to a combination of slight variations of pressure, temperature and/or humidity in each one, before and during its ascent. This contrasts with the laminar (smooth) bases we often see in supercells, where the vertical pressure-gradient force compels a sheet of air to rise along a gently sloping path (along an isentrope) to a less locally-variable LCL, then ultimately to its higher LFC, where now unshackled from CINH, it really goes ballistic and rockets upward at speeds even faster than CAPE alone can support. In this specimen, LCL and LFC were either roughly the same level, or LFC was lower (free convection occurring before saturation).
::::: End meteorological interpretation :::::

Back to the chase… This stunning view (17 mm wide-angle), looking W from 6 W of Cheyenne Wells back toward Kit Carson, compelled us to stop for a spell, knowing that the forward-flank core would move overhead and force a southward turn of our own soon. Little did I know that this most unlikely-looking of high-based High Plains storms was about to produce a tornado.

See the precip-filled occlusion slot in the lower middle of the last photo? A few minutes later, as I was gawking and babbling with semi-coherent admiration at the sky-filling structure, I heard Elke yell, “I think there’s a tornado in there!”

Me: “In where? No way!”

Elke: “Right there!”

Me: “Right where?”

Elke: “In there!”

Me: “In WHERE???”

Elke: “In the rain! Behind the updraft!”

Me (fumbling with camera gear): “Come on, from that storm? There ain’t no…hmm, wait a minute. Holy $%#^, that is a funnel in there. Get on there, stupid zoom lens. Dust! I think it might be a tornado!”

As usual, she was right. At least this time, she didn’t have a road atlas with which to hit me. 🙂

It was short-lived (~3 minutes), a long, slim, very stretchy condensation tube that began to break up even as I finally got the zoom lens attached and snapped the photo. The enhanced crop shows some of the dust it had spun up from the dry fields beneath. Other observers who were closer to the cheezenado’s location (SE of Kit Carson) also pegged it on a couple of SpotterNetwork icons, as I saw later once regaining data coverage. It was a flimsy excuse for one, but still, WFO GLD’s first tornado of the season. [The reports on the day’s rough log actually were of that one event, seen/reported from different places.]

As we dropped S out of the Wells, the brief spin-up soon became almost a forgotten sidebar in the face of one of the most fantastic and bizarre visual appearances I’ve seen from any storm. At that point, other cells were merging into its back side, with an initially separate storm base visible in the more distant W.

The supercell quickly was evolving into a small forward-propagating MCS, ralphing even more outflow. The resultant, bigger storm cluster formed a pretty, tiered shelf on its E edge (looking NE). Back to the WNW of us, an outflow-undercut but visibly rotating convective column briefly formed and poked into the ambient cloud base, adding more morphological weirdness to the whole event. The earlier “rear” storm, visible in the last shot, also was growing bigger, getting closer and becoming outflow-driven.

Pulling into the same Sheridan Lake petrol station where we had been the day before, I fueled up and spoke with some familiar faces behind the counter. “We’re back, and we brought another storm with us!”

I also chatted with Chris Weiss of TTU, whose Sticknet teams I had seen deploying their wares along US-385 as part of some sort of outflow-measuring experiment. [They had arrived at the storm right after the cheezenado and didn’t know about it.] That bunch should have acquired a great dataset; for the gust front soon barged through town unabated and well ahead of the main core, which itself turned left and barely missed to our E.

A few minutes later, a very concentrated and suspicious-looking, but non-rotating, dust bomb rose to the SE. Plow wind! The dust plume fanned out, advected away and eventually dispersed, as we turned back N for the 63-mile drive to ITR and a favorite motel there.

Along the way, several elevated and very high-based storms formed atop the cold pool from the earlier complex, including this one just S of ITR. South of town, we enjoyed a splendid sunset sky while parked in between wet plowed fields, and while talking to Rich T on the phone. He had seen his first tornado of the year that day–400 miles to our SE, along the OK/KS line W of BVO. We were glad for that too, as his chase fortunes this year had been awful so far.

After three days of beautiful outflow, we were ready for some meaty supercell action as portended by richer moisture and stronger shear forecast for the next day.

Second Dose of Beautiful Outflow Dominance

August 20, 2011 by · Comments Off on Second Dose of Beautiful Outflow Dominance
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Limon to Sheridan Lake and Lamar CO
17 June 11

SHORT: Intercepted two supercells that quickly became outflow-dominant in east-central CO. Picturesque structure. Nighttime lighting, mammatus and moonrise show near Lamar CO.

LONG: Starting at the laundromat in Yuma, we headed S at midday toward a forecast initiation area near the Palmer Divide, which by the time we hot the open plains S of town, already bubbled with tall convective towers. As in the previous day, I was concerned that storms would go too soon and create a big outflow surge; but instead they percolated for some time, struggling to organize as we approached LIC. There, we sat under the NE edge of a high-based, fuzzy, virga-spraying line of cells, none particularly impressive for about an hour.

Finally, as so often happens on these highest of the High Plains, a few distinct updraft bases materialized from the mush, one of more of which I guessed would evolve into a supercell, given both the favorable deep-layer shear and increasing low-level moisture content with time. When some of the virga started to reach ground as rain in LIC, we zipped several miles S of town then W a mile on a dead-end dirt road to watch the action unfold, while remaining in at least marginal phone-data coverage of LIC’s cellular towers. Turns out we didn’t need the data…as often is true out there, the eyes have it.

Two supercells developed essentially in sync — one to our somewhat distant W beyond Simla, the other to our NW between Matheson and LIC.

The closer storm evolved fast, and in fascinating ways. The initially broad, high updraft base in the last photo lowered somewhat, with a broad, ragged cigar of scud materializing beneath as the updraft began to process rain-cooled air from the neighboring parts of the forward-flank core. Notice, in the last photo, the lower-middle part of the scud bank seems to be rising off the ground. In fact, it not only was rising, but weakly rotating–before the broader scud stogie ever attached to the parent storm’s cloud base: a “scudnado” indeed! The scud mass kept growing and rising, becoming part of the storm’s updraft base and lowering it tremendously. This is a classic example of a storm modifying its own thermodynamic environment to ratchet down its own LCL!

Meanwhile, we saw intermittent chunks of ground-based scud, rising and slowly rotating. Nothing appeared too threatening from the standpoint of developing a real tornado, but it certainly kept my attention, in case the circulation ever started to tighten up to ominous levels. Some of them certainly had that look (zoom lens and enhanced digital zoom). I was pleasantly surprised and glad to see that nobody called these in as tornadoes, knowing that a lot of chasers were roaming about the area (based on Spotter Network icons). Another example a few moments later: (zoom lens and enhanced digital zoom).

The first supercell moved ENE over the LIC to our N, and gusted out. That turned our attention to the second (western or “Simla”) storm, which had sported intermittent, mostly non-rotating and ragged lowerings so far. A large, weakly rotating and precip-wrapping wall cloud developed as the storm drew closer, thanks to a a big mass of rain-cooled air entrained into the main updraft region. The supercell turned hard right, heading ESE and bearing the forward-flank core on course for the location where we comfortably had parked for about an hour. Time to head S again…

N of Punkin Center, we stopped to the updraft’s E again, this time for a short spell to photograph some beautiful clean-air storm structure. The supercell grew ever more outflow-dominant by the minute and accelerated its forward speed, so we couldn’t stay long. One more shot of the striking form of the storm, a marvelously textured swirl of gray shades and turquoise looming across the western sky, and it was time to bail over toward Aroya to open up some room between the storm and us. Along the way, its gust front briefly passed to the NE and to the N.

Approaching Aroya, we remembered a beautiful, old, abandoned schoolhouse we had seen on another chase nine years ago, having wished someday to photograph it before an approaching storm. This was our chance! The result is one of my favorite Great Plains scenery shots of the year so far.

Near Wild Horse, the supercell tried hard to enlarge a surface-based updraft, and appeared to succeed. The result was another spectacular display of texture and shading. Yes, that lowering at the inflow-outflow interface was rotating–slowly, but helically, giving me some concern for a brief tornadic spin-up. This one (zoom, and enhanced zoom of a zoom) compelled me to call, but thanks to being in one of the many tens of thousands of square miles of the Plains that constitutes AT&T’s 3% of America not served, I had no signal.

Fortunately, that feature quickly dissolved under relentless assault from cold outflow. Shortly after those shots, YF Umscheid motored up the dirt road toward us from a vantage closer to the feature, without reporting anything of consequence. We stayed ahead of the storm as it surfed outflow, driving E to Cheyenne Wells then S to Sheridan Lake. Between those burgs, we stopped to photograph the increasingly high, tiered, arcus-like eastern part of the base and a pretty array of sunset tones on the W side.

The storm now being a windbag and dust-bomb, we left it to get some lodging in LAA, setting us up for a long-desired revisit of Bent’s Fort and perhaps another chase opportunity the next afternoon off high terrain near and S of the Palmer. We found a nice, locally operated motel, then headed just SW of town to watch a short-lived, probably elevated supercell approach in the fading twilight. Elke was getting tired, so we went back to the motel, as the storm peppered town with abundant hail up to 1 inch in diameter (definitely smaller than the supposed “golfball hail” in the local storm reports).

A good lightning show beneath and on the back edge of the storm sent me back S of town again onto a different side road, this time to photograph the mammatus-festooned electrical show from the rear. As crickets and frogs sung loudly from every point of the compass, that amazing moist-earth smell refreshing my spirits amidst cool outflow air, the lace-lightning display continued with the storm’s eastward retreat. As a bonus wonderment, to cap a fine storm day, an orange moon rose beneath and then behind the distant updraft base. In the last shot, above the flanking line, you can see the anvil edge illuminated by the moonlight, in addition to the lighting by lightning within the storm.

After a long and satisfying chase day, we slept very soundly that night!

For your enjoyment, and as a reward for patiently reading this far, I’ve thrown together a couple of coarse animations from tripodded still-camera images shot that night: the first of the retreating storm with lace lightning, and the second of the wide-angle moonrise scene.

Colorado Kick-start

June 30, 2010 by · 1 Comment
Filed under: Summary 

Bennett and Limon/Genoa area supercells
11 Jun 10

SHORT: Outflow dominant supercell intercepted E of DIA airport, followed by cyclic complex of supercells from LIC to E of Genoa CO.

The previous morning, I got off a night shift at 8 a.m., and Elke and I made a dash toward the NW to see how far we could get toward that day’s (and definitely this day’s ) best storm potential. Unfortunately, she got sick in NW KS and we had to stop in Colby for the afternoon, a couple of hours short of the tornadic Last Chance storm.

To be able to chase at all on the 11th was a blessing, given that Elke had to go to a local clinic to get diagnosed and treated for some terribly painful digestive problems. Not only did we chase, we saw some very interesting storms and met old friends. Elke was cleared to travel, though we had to make reasonably frequent stops for the rest of our vacation so she could stay hydrated and keep the innards moving as they’re supposed to.

I considered two potential target areas — one being a highly conditional potential near the warm front and E of the surface low in north-central/NW KS, where storms might never form, but if they did…look out. The other was the more dependable (for initiation and photogenic structure) but probably not as tornadic upslope region of eastern Colorado. This being our first full day out, and having been unable to get to the Last Chance storm the prior day, we aimed for the Colorado target area.

After meeting the Three Dudes and Two Dogs chase team at Burlington for some pre-storm banter, we headed W on I-70 to LIC, mooching wi-fi from a motel while parked across the road from a lot of V.O.R.T.EX.-2 vehicles. Eyeballs and data showed a nicely destabilizing air mass up and down the Front Range, almost no CINH, lift in the form of heating and upslope winds on the higher terrain, and rich moisture for the altitude, beneath robust deep-layer shear — in other words, a recipe for supercells lacking no ingredients, save the storms themselves.

It didn’t take long. A supercell blew up quickly in the Front Range mountains SW of Golden, where Elke used to live, and started churning NE across the Denver metro. Not wanting to chase in the city, we scooted to a high spot a few miles E of the airport to observe the cycling, already somewhat outflow-dominant storm. A new updraft that went up on the SE side of the storm sported a rotating wall cloud in short order, but that soon got undercut by outflow from the hail-spewing HP mothership. Shortly afterward, several V2 vehicles showed up, including occupants and friends Ken Dewey and Tim Marshall, who looks as if he is about to be struck be lightning in this photo with me. Fortunately he wasn’t, since we both would have been killed.

The storm’s motion began to accelerate as it surfed its own outflow, and we bailed S to I-70 to intercept a younger supercell rolling off the highest segment of the Palmer Divide toward LIC. Along the way, we saw several lowerings, looking S and SW through the core and through precip gaps to the mesocyclonic region, but no obvious tornadoes. We found a nice road a few miles SW of LIC and, for one of the few times so far this year, had the luxury of staying in one spot for awhile and letting the storm move to us.

Our first view from the inflow sector revealed a somewhat high-based, HP storm with a deep core surrounding the mesocyclone area. Sherman Frederickson (former NSSL colleague from the 80s), Howie Bluestein (one of my professors from back then) and several students were occupying a radar truck just up the hill behind us, and Howie was gracious enough to invite me up into the truck for a peek at their live scans of the mesocirculation — impressive, but endangered by heavy precip from two sources…

Things got complicated on the storm scale. A temporary new occlusion with small wall cloud formed ahead of the HP core, but that attempt got short-circuited by cold outflow from a large, heavy shower that formed in the storm’s immediate inflow region (ultimately moving over us and merging with its forward flank). In increasing rain, we decided to get E of LIC near Genoa, E of the messy storm processes unflding, and let things evolve again while moving E toward us.

An elongated supercell complex with embedded mesocyclones emerged from the chaos, while we parked and chatted with the eccentric old proprietor of the uniquely quaint Wonder Tower (“See 6 States”). As the convection reorganized, I shot photos looking over the tower and store and looking N from its back lawn at storm scenes, while Elke toured the antique shop and bought some old bottles.

While I was composing the former shot, I had a friendly yet disturbing encounter with a newbie chaser who had “learned the ropes” (very frayed and thin ropes, as it turned out) on a few years of chase tours. If you’re interested, read more about it in this Weather or Not entry.

Soon afterward, north of the shelf cloud, a violently rotating mesocyclone developed rapidly, in a notch region between core and gust front to its S. This compelled us to wander over to the next viewing spot W of the tower for a closer look. The circulation was spinning so fast, I thought it would plant one any minute. The rotating cloud mass, eerily front-lit from the E, its base atypically low for Colorado and black as night, entirely filled this wide-angle view. The circulation was only was a mile or so away and moving toward us. If a tornado were to form at thus juncture, it would have been be precariously close to I-70 — a most undesirable outcome. I rather would not see a tornado than for one to move down the Interstate, throwing vehicles every which way. Indeed, no tornado developed during this stage, though a quick spin-up did occur between Genoa and Arriba N of the road, as we evacuated rapidly eastward.

By the time we got past metropolitan Arriba, the Genoa circulation either weakened or merged with another to its N, sporting a well-defined mesocyclonic notch — and occasionally, ragged, slowly rotating lowerings beneath a wall cloud, but no obvious tornado. We briefly talked with Al Pietrycha and Pam Varney Murray near Arriba…good to see them again!

The whole complex lined out and weakened, so we headed to Burlington for the night. Visible to the distant ENE: a monstrous explosion of convection out of our reach, in KS, that produced a few tornadoes while remaining nearly stationary, right in my conditional forecast area. I tried some nighttime lightning observing and photography on the back edge of the Colorado line after it moved past us, encountered more inflow moisture and re-intensified, but it was mostly a bunch of in-cloud flashes, diffuse filaments and distant CGs. So it goes…without regrets, we were pleased with the day’s adventures and ready for another.