Millsap TX Tornado and Supercell

July 18, 2013 by · Comments Off on Millsap TX Tornado and Supercell
Filed under: Summary 

Brock TX
15 May 13

SHORT: High-based junk storms watched near ABI. Headed E on I-20 toward confluence-line towers moving into high-SRH environment. Saw eventual Granbury supercell looking S and almost went after it. Instead took direct I-20 route to explosive, then-bigger storm to our NE. Watched excellent structure, brief/weak tornado(es), longer-lasting Millsap tube, and messy/multi-vortex circulation from Brock exit. Road-screwed for both storms after that. Tried to glimpse South Dallas storm after dark, too much rain.


Pre-storm setting and early dryline convection
In a year that had been rather scant for observable tornado potential, we didn’t truly expect this day to yield much, either. Maybe it was pessimism. Maybe it was an unspoken wish not to jinx the chase, despite our disbelief in such paranormality. Maybe it was the peculiar pattern, with some split flow and the shrunken remains of a southwestern upper-level low slowly ejecting across Oklahoma. [For decades, didn’t Al Moller often extol the virtues of split flow aloft for outstanding Texas chasing?] Maybe it was the vibe that this was one of those down years (shown to be decidedly false by month’s end).

Reasonably large hodographs were reasonably forecast for part of north-central and NW TX, but generally displaced 100 miles E of the dryline, near the western lobe of a corridor of very mist return-flow air. Perhaps if an initially high-based storm firing off the NW TX dryline bulge can last long enough to get into that returning moisture and backed surface flow before dark, it could get happy. Perhaps this, if that…you know the saying: “If ifs and buts were candy and nuts, it would be Christmas every day!” Whatever the reason, we headed southwest on a classical spring chase trip to NW TX talking supercells but not tornadoes.

Rich and I decided to play the belt of enhanced midlevel winds and deep shear, S of the OK low aloft, W of the northward moisture bulge and E of the eastward dryline bulge. Initial target was the Haskell-ABI area, with (naturally) the season’s first Allsups burritos consumed along the way in Seymour. While at an abandoned farmstead N of Anson, the first deep towers erupted just to our WSW, practically in our laps and as if on queue.

However, more, even deeper towers could be seen in the hazy distance SW of ABI. Not seeing an appreciable difference in the environment of either, and both being in our target area, we decided to head toward the southern towers and keep the northern ones in view. The southern convection stayed more vigorous, and even garnered a severe warning–but turned to virga-blowing mush by the time we got S of ABI and in good intercept position to its E.

Meanwhile, the high base of the original convection, now two counties (or about 50 miles) to our N, could be seen clearly despite its distance, beyond the anvil material of the dying ABI storm. A quick check of the surface map and objectively analyzed moisture and CAPE fields revealed that the northern cell was a flimsy hope for making it far enough E to tap the reservoir of upper 60s surface dew points S and E of MWL, and (for now) shallow but building towers could be seen in the distance, corresponding to a confluence line located along the W side of the moist plume.

Maybe the northern storm somehow could get far enough east (unlikely). Maybe the cap could weaken enough along the confluence line to blow a storm or two and send it into the good juice (an intriguing but highly conditional possibility at that point). For either scenario, we would need to head back to I-20, then ENE at least 50-60 miles. If ifs and buts were candy and nuts…

As we scooted E of ABI and the northern storm shriveled, we were at our most pessimistic, as were many other storm observers–some of whom immediately abandoned the chase to start heading NW toward forecasts of central High Plains storm potential in the following days. We didn’t have that option, and besides, something very intriguing was happening across the eastern sky.

Target shift
We hung our hopes on those gradually deepening confluence-line towers–convection that got ever deeper and thicker as we rolled along the slab. The closer we got, the better it looked. The bigger towers began to sort themselves into young storms, and some of the development to our SE, ESE and ENE looked like it was going to erupt into big action very soon. The situation definitely was passing the eyeball test for those of us who have been doing this awhile.

Parameter check: effective shear was fine…SRH increasing E of the confluence line…CAPE was large, and we know what big CAPE does. Accordingly, an elongated bull’s-eye of significant tornado parameter (an index we invented, so we had better pay heed!) showed up and increased downshear from the building storms and W of I-35.

I could detect the scents of delectable convective comestibles cooking in the kitchen of the sky, soon to be placed on the smorgasbord of atmospheric violence for us to devour! The question was becoming: which entree shall we select?

By the time we approached exits leading to BWD and MWL, one healthy-looking storm already was beginning a right turn near BWD, and was warned. Two younger and closer ones were apparent and looking robust visually, but not yet as impressive on radar–approaching SEP (this became the eventual Granbury/Cleburne storm) and near MWL (the eventual Millsap storm). We had our pick of the litter, and ultimately wouldn’t have gone wrong with either of the two closer choices. Though the southern one of the closer pair initially was smaller and took longer to mature, it ultimately produced a violent tornado in deepening darkness. We briefly stopped briefly to look S at that young, future Granbury/Cleburne storm to our SSE, small but already showing some visual supercellular characteristics.

Meanwhile, the cell near MWL went berserk in ten minutes–two volume scans–explosive towers evident through intervening low clouds in the near NE sky, and remarkably rapid growth in areal coverage on the radar screen. Between that trend, the choppier terrain in the path of the much smaller SEP storm, the presence of an Interstate to take us straight to the northern storm in legal haste, and the poorer road options S of I-20, we quickly selected the MWL cell for close investigation. Along the way, and between hills and other obstructions, we saw a wall cloud quickly form and occlude (without tornado) under the base. This storm went from disorganized mess to serious supercell in less than half an hour, and as Jim Leonard might say, “This is serious business now”.

Smorgasbord delivered
Finding high yet accessible vantages in that part of north TX is a challenge; so we grabbed the easiest and first spot we could find in the storm’s inflow region — a staging area for construction work right off the Brock exit. Unfortunately, this means there is road-work material and/or the Interstate in the foregrounds of some of the images; but I guess they tell a story and add some foreground texture too. As for the storm, what a structural delight that greeted us! We remained at this spot, or just across the overpass (later stages) through the entire tornadic stage of this storm.

One fairly low wall cloud developed while the storm still had most of its spectacular deep-layer structure visible, with a turquoise tinge starting to show up in midlevels. A few minutes later, around 1841 CDT, a funnel (deep enhancement) developed on the near left edge of the wall cloud, with scud sometimes rising rapidly right off the ground and more slowly rotating into it as part of a distinct, helical column. It was about as weak and low-end of a supercellular tornado (deliberately underexposed zoom) as one can imagine, but nonetheless, there it was. This little vortex lasted just 2-3 minutes and whetted our appetite for more.

In the succeeding 20 minutes after that “wimpnado” ended, a big gob of rain slowly wrapped around what was left of the wall cloud — now becoming ill-defined — in the form of a precip-filled RFD. Then, at 1903, another funnel (deep enhancement) became apparent within the translucent bear’s cage, a little more distant from us (maybe by a couple miles) than the first vortex, and near Millsap. Though no power flashes were visible, faint and low-contrast ground contact of condensation in these early stages confirmed another tornado for us–albeit cheesy at this stage.

Quickly, the whole mesocyclone wrapped deeply in rain and completely obscured any remains or evidence of a tornadic vortex within. As such, we do not know if there is true physical continuity between that vortex and the next one in the same general area. However, this view at 1907, as the precip began abating and the mesocyclone got more deeply occluded, shows no obvious visible evidence of a continuous tornado.

Here’s the next visible vortex! This showed up suddenly at 1909 (deep enhancement), representing the start of the “Millsap tornado” that many observers watched. It may or may not have been continuous with the previous tornado. Some translucent curtains of rain still were orbiting this increasingly deeply occluded and quasistationary meso. The tornado became better visible as a classical, partly rain-wrapped cone beneath a scuddy and ragged storm-scale circulation.

Meanwhile, the parent supercell was moving slowly SE, away from the tornadic circulation–effectively kicking the old occlusion farther back through the rear of the storm. A new mesocyclone started stem-winding just ENE of us by just a mile or two, at most. We had to keep our heads on a swivel, watching the adjacent, tightening area of rotation while admiring the tornado from a greater distance.

Look here, look there…left, right…look here, look there! Someone watching a camera trained on me might have thought I was observing a slow-motion tennis match. Unfortunately, I didn’t shoot the closer meso yet because our ideal tornado vantage on the SW side of the interchange put the Brock Road bridge in the way of seeing much beneath the circulation that was practically in our laps. What a mesocyclonically bipolar conundrum! I was ready to run over or under the bridge, however, to shoot right down the Interstate in case the nearby circulation tightened to tornadic intensity.
It’s a good thing that didn’t happen yet, because the meso was smack-dab over the road to our immediate ENE, with a good deal of truck traffic zooming this way and that.

With the tornado still in progress to the NW, a brief, small funnel appeared to the N, but with no ground circulation evident beneath. The funnel sprouted from the cyclonic-shear zone (and likely ribbon of low-level vorticity) in between but connecting with the two mesocyclones. Clearly, this was a much different environment than our moisture-starved convection out by ABI.

Back on the occluded, certifiably tornadic area NW of us: the rain gradually fell away to reveal a classical tornado specimen in its full splendor, going through assorted conical forms from nearly symmetric to tapered and curved for several minutes, finally roping out with a twist. A detached condensation puff marked this tornado’s dissipating gasp at 1919, and its parent mesocyclone very quickly followed suit.

No time existed for basking in the joy of a harmless and beautiful tornado as just seen. The nearer mesocyclone actually retreated N of the Interstate, exhibiting a similar storm-relative backtracking as the precious attempt–but without the long-lasting, high-contrast tornado. Instead, it offered a short-lived, fuzzy, scuddy, ragged, multivortex circulation that lasted 2-3 minutes starting around 1922. We promptly drove the hundred yards or so back onto the eastbound service road and over Brock Road to get a better view, by which time the multivortex action to our NNE had consolidated beneath a fat little tube that was coiling ragged scud off the ground.

Fortunately, the brief tornado continued to back away from the Interstate, soon dissipating. Yet another meso was developing downshear, a few miles to our SE, as the supercell jumped flanks.

Decisions in Dallas darkness
Unfortunately, this southeastward, effectively discrete propagation led us right to the W edge of a road void ENE of Dennis, looking E at an increasingly rain-wrapped meso. We had no viable option back around to the inflow side, and no view within. A very well-defined radar hook, a tight velocity couplet, and rapid N-S precip motion on the back side left us wondering just what was happening “in there”. The precip was just too dense to see through, and the viewing angle was bad (except for the rainbow across a field of flowers).

Refreshingly rain-cooled air, tinged with a blended floral and earthy scent, carrying bird songs, was a consolation for an inability to ascertain what the later storm reports indicated was nothing of importance happening inside the mesocyclone. We surprisingly encountered Jack Beven and Margie Kieper on this remote stretch of unmarked back road NNE of Dennis; they had seen the main Millsap tornado from the distant E after a late start from visiting friends in the DFW Metroplex.

We all could have made the loopy plunge southward to intercept the now tornado-warned Granbury-Cleburne storm (whose flanking towers were visible and not far away) at or just after dark. Common sense prevailed. Core-punching a tornadic supercell, from the N or NW, on twisty and hilly roads with few escape options, in deepening darkness, did not appeal. Instead, Rich and I grabbed dinner at Whataburger in Weatherford, then headed back toward FTW for the turn northward and homeward.

Along the way, a small supercell with a nice hook erupted over Arlington and cruised E across the Oak Cliff section of SW Dallas. meanwhile, the Granbury storm was headed ESE toward I-35 and could have been targeted (again, we decided against that). Though it was dark, the projected path of the smaller Dallas storm took it toward south Mesquite; so we jumped down to I-2o to get into its inflow region. Very shortly after doing so, we encountered a huge traffic jam…going the other way! A wreck had the westbound Interstate backed up for miles; but our side was smooth sailing. Before we got into decent position SE of the storm, though, a dense cluster of heavy showers formed and moved right over us; their outflow weakened and ultimately killed the south Dallas supercell. We turned N through its feeble remnants, wheeled around LBJ freeway and drove on back to Norman through occasional elevated storms.

A north Texas chase day finally bore fruit for us with a classically structured supercell and a few low-impact tornadoes casually observed from one spot. The bad news was that the storm we didn’t chase (and wisely so) produced a terrible killer tornado near Granbury, and a big, destructive wedge after dark, around Cleburne. This marked the sad day that the switch had flipped on from a shockingly inactive tornado season to a dreadfully busy and tragic two-week stretch, at least for the southern Plains.

Those Northern Plains Convective Skies

December 21, 2012 by · Comments Off on Those Northern Plains Convective Skies
Filed under: Summary 

Medora to Hettinger ND, Lemmon SD
13 Jun 12

SHORT: Rewarding day considering low expectations. Scenic initiation over badlands of Theodore Roosevelt NP. Intercepted subsequent splitting storms along ND-SD line, with dominance of slight leftward motion. Ended chase on E end of high-based storms between Buffalo and Faith SD.

We had enjoyed a few days of casual exploration in the Turtle Mountains and Peace Garden area, followed by exploring and photographing the North and South Units of Theodore Roosevelt National Park (TRNP) of North Dakota. The North Unit offers great hiking and few people…I highly recommend it for both geology and northern Great Plains landscapes!

All that was done while awaiting the next northern-stream shortwave trough, the system finally approached. This day offered the classic storm-intercept targeting conundrum of mid-June–stronger flow with weaker moisture up north, or vice versa farther S. Since “farther S” was New Mexico in this case, we stayed put, having found one of the few reasonably priced motel rooms in the region at one of the most inappropriately named towns on the Great Plains–Beach, ND. If you’re chasing in western North Dakota, be duly advised that rooms are scarce and expensive, and likely will remain so for the foreseeable future, because of the boom in fuel extraction from the deep Bakken Shale formation.

Fortuitously, the morning forecast scenario indicated storm initiation would occur near a slow-moving cold front and inverted trough over northwest SD and southwest ND–maybe even very close to us at TRNP. So…we cruised over to the South Unit of TRNP for some scenic hiking and driving in the morning, followed by lunch in Medora, and a grand plan to commence storm observing over the badlands of the South Unit in the mid-afternoon.

Towers already were erupting along overhead and to the S, when we were finishing a late lunch in Medora. We headed several miles E to the Painted Canyon area of TRNP and set up for a few DSLR time lapses of convection over the scenic North Dakota badlands. Here are some still shots from those, looking N and looking NE.

Those photos are part of several speed-adjustable time lapses I made from timed photos at those locales…be advised that these time lapses may load slowly if you’re on a low-bandwidth connection:

  1. Three time lapses looking N at convection forming along the boundary (time lapse 1, time lapse 2, and time lapse 3) looking N at the convection forming on the boundary, and
  2. My favorite, a longer time lapse I was able to build looking NE from essentially the same place.

Another clump of towers deepened marvelously with a mesonet site in the foreground. This told us the atmosphere was ready to do something special, the main question being, “What, exactly?”

Setting forth southeastward across southwestern North Dakota, we stopped occasionally to watch assorted towers build beautifully, ever deeper, ever grander across a verdant Northern Plains landscape. Several Cbs within a 75-mile radius offered themselves for targeting. This upwelling of atmospheric splendor to our NE, near New England (the town) tempted us, but the updraft and base on the N (left-inflow) side looked better than that on the near (right-inflow) flank.

This storm, and most others on the day, were either splitters or left-movers. Despite the decent deep-layer shear, small low-level hodographs kept storms from becoming too rightward-dominant, and therefore, from being long-lived cyclonic supercells.

Leaving that cell as it left us, we zigzagged farther SE toward Hettinger, to intercept another cell that was looking larger and more robust, visually and on Bismarck radar. We couldn’t quite reach our E option (US-12 near Bucyrus) before the storm did, so we let it cross the road with the abandoned Hettinger Equity grain elevator in the foreground. Being high-based, the storm traversed above a deep and slightly moisture-deprived boundary layer, producing a strong theta-e deficit in its immediate wake. Profuse hail up to an inch in diameter contributed to that localized cold pool, too.

Following the storm eastward, we saw more rainbows, finding the pot of gold not in a literal sense, but in the splendor of a convective Northern Plains sky, a treasure beyond measure, intangible and ephemeral yet perpetually memorable.

Being behind a storm, especially one that’s not terribly speedy and that likely won’t produce a tornado, often can be more photogenically rewarding than being in its way. Seldom was this more true than when we pulled beside a moist, rain- and hail-cooled field E of Hettinger for a tremendous view of the receding Cb brightening the northeastern sky with its convectively reflective brilliance. It was a great way to bid good-bye for the year to North Dakota–a state where they use spruce instead of cedar for wind rows (as seen in the last two shots), a state that had treated us very well convectively and otherwise over the preceding few days.

We dropped ESE obliquely across the South Dakota border on US-12 into Lemmon, noticing new development to our distant WSW, S of Buffalo. Without any decent, intervening north-south roads, and with the newer storms growing upscale and moving fairly rapidly, we headed S on SD-73. This also would take us closer to Belle Fourche, where we had made lodging reservations for the night, in anticipation of a meteorological down day spent at Devils Tower WY. We watched the very high-based, south end of a line of storms approach, laden with wispy tendrils of windblown precipitation, then dodged southward out of its way and into a twilight adventure driving to Belle Fourche.

We knew it would be an exasperating ride when we saw a sign, “ROAD CONSTRUCTION NEXT 47 MILES”. Although no actual, active construction was taking place, we ended up driving for about 25 of that 47 miles behind an 18-wheeler, on a rough, 1-2 lane dirt version of the state “highway” that featured sudden and unmarked lateral shifts in road position within its right of way. The truck drove off the road several times and back on again; so we couldn’t depend on its driver to guide us regarding upcoming jogs in the roadbed. We did, however, have to suck the dust, even while staying back a few hundred feet.

Needless to say, we got into our motel later than hoped, tired from the unexpectedly weary ride in, but thankful for one of the most purely pleasing convective days of the year.

Beauty of Outflow Dominance

August 11, 2011 by · Comments Off on Beauty of Outflow Dominance
Filed under: Summary 

Nebraska Panhandle Bow Echo and NE Colorado Dry Downburst
16 June 11

SHORT: Fun day. Began in Hot Springs SD. Observed/photographed spectacular outflow-cloud structures (shelves, bands, stripes) with raging bow echo/haboob from BFF to N of SNY. Dropped S for peculiar, photogenic dust storm and sustained damaging gusts beneath high-based N rim of eastern CO MCS.

LONG: Back onto our storm-observing trek after a couple of amazing days in the Black Hills, flow aloft and at least marginal low-level moisture were beginning to juxtapose favorably once again to our south. We targeted the nearby Nebraska Panhandle for the prospect of high-based storms rolling east out of the higher terrain of eastern Wyoming. Browsing the morning maps, I was confident in upslope flow into that orography, along with afternoon storm initiation…but would there be too much, too soon, before the richer moisture could arrive in the evening? This scenario would mean outflow dominance.

Still, a conditional triple-point play in south-central KS was much too far away; and the mountains ain’t going anywhere. Blow increasingly moist air into them for enough time during daytime heating, and storms will form. Our goal: be downshear and see what evolves. High dew-point depressions portend shelf clouds, dust and high wind from storms; and sometimes that can be beautiful too.

And so it was…

We drove to favorite overlook SW of Angora upon which we had perched a few days before, watching the top 4/5 of assorted towers build and glaciate over the unseen mountains of eastern WY. Finally, when the storms started to coalesce and move off, one of which looked like an embedded supercell on radar, we headed W to the N edge of BFF to watch them roll downhill right at us. By then, the supercell was hard to distinguish in the onrushing wall of a dark, ominous, and increasingly well-defined squall line.

Reflectivity animations confirmed that the northern segment — basically due W of us, was bowing out. It was time to go outflow surfin’! Stay ahead of these, and they can offer some absolutely stunning cloud structures, such as the following three-piece view from between BFF and Minatare:

    Looking NW: I’ve never seen a combination of lightness, darkness and radiating cirriform streamers like this before!

    Looking W: Right into the teeth of Jaws. This is what a bonafide bow echo looks like when it’s “a-comin’ ta gitcha”. Check out the peculiar translucent strands, reminiscent of Silly String, festooning the otherwise featureless midlevel cloud deck. It might seem hard to photograph the strong dynamic range between the ink-dark core and the otherworldly apron of light above and beyond the shelf cloud; but not this time. This is how it actually looked, with no HDR bracketing necessary! I just had to meter for the area smack in the middle.

    Looking SW: A classic view of an onrushing convective windstorm on the High Plains, this time with the Wildcat Hills lining the southwestern horizon.

We stayed ahead of the snapping maw of this storm — barely at time, I must admit — all the way to Bridgeport and beyond — before bailing S to let the road-deprived Sandhills have their turn at it. We got one last nice view of the atmospheric earth-mover raging to our NW before turning equatorward. What a gorgeous display of outflow-driven stormscapes we had witnessed!

Now it was time to get out of the way and figure out what to do with several more hours of daylight. Some storms had fired in NE CO, likely to be just as outflow-dominant and perhaps quite high-based. From SNY, it wasn’t that far away, and the next two days looked like potential Colorado storm targets anyway. As such, went back through Sterling again (retracing a good deal of our chase path from BFF three days before).

Unlike then, the Centennial State sky greeted us with a giant field of decaying storm material — virga dropping from various patches of agitation beneath a widespread anvil shield that once contained actual updrafts. N of Otis, a wall of wind slammed us in an impressive dry downburst, tearing dense channels of dust from plowed fields, buffeting the vehicle laterally with shot after shot of very localized wind-force lasting a second or so apiece, and making me struggle with the wheels to maintain positioning on the road. Good thing I had new tires for this season…

After a late rainbow and dinner at a familiar restaurant in Yuma, we bunked down there for the night, satisfied that we made the most out of a very windy storm day.

The human element of storm observing always has some interesting twists and turns too. We had a few loud neighbors at our motel, getting drunk and cussing in Spanish, and after a spell, I thought I might have to go out there and shut them up by request or otherwise. Fortunately for everybody, the former worked. The ringleader turned out to be cut from the cloth of my old barrio associates from long ago: he was wearing a shirt that said, in Spanish, “Don’t f___ with the DALLAS COWBOYS”. All day, I already had on my trusty blue-star cap. After some conversation about America’s Team, they retreated to their rooms, an elevated storm blew by with an intermittent show of close CGs, then off to bed everybody went.

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