In the Dust Bomb

July 23, 2013 by · Comments Off on In the Dust Bomb
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Protection KS
18 May 13

SHORT: Intercepted outflow-dominant mess of storms in SW KS with gustnado and dusty air currents.

LONG:
Favorably strengthening mid-upper level winds were expected to boost deep shear atop an increasingly well-defined dryline that, by mid-late afternoon, would set up on the east edge of the central and southern High Plains, near 100W. We had diagnosed an 850-mb dry slot left by an earlier wave aloft that was likely to lead to a shallower and more easily mixed moist layer over potential NW TX and western OK dryline targets, leaving is with western KS. The closest available part of western KS to us was southwestern KS. Hence, that was our rough target on this “day before the day”. Very rich moisture and backed surface flow were expected to reach parts of west-central and southwest KS before dark, but could it get there in time to be tapped by storms that likely would fire off the dryline beforehand?

Out the door early enough, Rich and I headed up the Northwest Passage, fueling and meeting the esteemed storm-observing firm of Fogel, Fogel, Weitzberg and Brown (and two heavily panting leonbergers) in WWD. There, we all were greeted by the full-body, hair-dryer feel of 96 degree F air blowing past. When the car thermometer (which is fairly well-calibrated in Norman to the nearby mesonet site) hit 101 deg F just across the KS line, between Sitka and Protection, we knew that was just too warm to preclude serious outflow from eventually taking over any storm that developed in that environment. However, we also expected richer moisture (supporting 70s F surface dewpoints farther E along the border) to advect into the area after peak heating, thereby lowering LCL and boosting CAPE. Which process would prevail first?

We all headed E back into the mid-90s heat, and a shady rest area near Coldwater where the big dogs could get out and walk some without suffering heatstroke. There we also met Ryan Jewell, watching towers bubble up and occasionally glaciate along the dryline from NNW-W-SW. The gathered crew (four of whom are pictured here) represented a large collective of storm-observing experience, which makes some of our decision-making this day even more peculiar! Since they may not wish to be positively, pictorially identified with this chase day, we may only know their monikers (l-r) simply as Big Dog Daddy, Downtown, The Roach, and Jumpin’ J-Hawk, with Gran Rogelio behind the camera.

Patiently this motley bunch awaited the arrival of the better moist layer that we could see in the form of haze and lower-based cumuli off to the E and SE. One of these, the high-based little Cb pictured here, moved NNE and eventually evolved into the Rozel cell. Had we known what it would do, we would have followed this seemingly pathetic little plume with mouth-foaming fervor. Alas, on this day, we simply did not. With this cell moving closer to the moist axis, I still can’t fully explain why we chose to go SW toward the bigger, messier activity coming out of the Panhandle and still in the drier air, except for some hopes it would not get outflow-dominant before reaching the richer moist layer we could see to the ESE.

Meanwhile, a storm farther N (and legitimately out of reach) was already tornado warned and apparently producing rain-wrapped circulations as it approached I-70. Longstanding convection in the northeast TX Panhandle and extreme northwestern OK was growing in size and depth, glowing with blood-red reflectivities on radar and a deepening visual darkness in the southwestern sky.

Someone mentioned the possibility of anvil shadowing cooling the temps, lowering LCL, weakening mixing, and perhaps allowing the moist layer to advect into the inflow region relatively unadulterated. It wasn’t bad reasoning, per se, but the large size and SW-NE, quasi-linear orientation of the cluster to our SW should have been a clue that it wouldn’t wait for the rich moisture before spreading its load of outflow all over the surrounding countryside.

As we approached via southwesterly zigzag, the cluster seemed broad and disorganized with some updraft area on the south and east sides. When we stopped, S of Protection, the updraft area obviously was getting undercut by outflow, and the high-based, multicellular mess started its predictable forward-propagational heave. Cold outflow blasted past us to the E and SE, and a weak gustnado buzzed eastward across a field to our NE.

Dust rose from roads and fields, jacked skyward and forward in dense plumes, scenes from the Grapes of Wrath swirling through our minds as ribbons of fine soil blasted past. J-Hawk photographed and sepia-toned two of us pathetically immersed in the lofted dirt.

Massive dust-bombing wasn’t why we drove over 200 miles, though it did offer its own interesting photographic adventures. Nonetheless, this was the hand we pulled from the deck. Richer moisture did move into the inflow layer of this storm complex, but by then it evolved into a raging, N-S squall line that ate up every other convective attempt in its path (including the tornadic Rozel supercell that had gotten entrained into its N edge). One last view of the convection at sunset, from near Camp Houston OK, and it was time to plod home, regrets over choosing the “wrong” storm tempered by hopes for the next couple of days of potentially significant tornadic potential closer to home.

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.

Atmospheric Underproductivity

May 20, 2011 by · Comments Off on Atmospheric Underproductivity
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NW OK and SW to Central KS

SHORT: Assorted convective towers over NW OK and central KS, mushy storms in SW KS, twilight macroburst in northern OK.

LONG:

One year to the day after a chase that was most memorable for all the right and wrong reasons, Ryan Jewell and I left Norman for the PTT area at about noon. We hoped to follow a dryline supercell across a narrow warm sector and then be there for its mature interaction with a pronounced warm front, and the mesocyclonic bliss such processes often entail. Alas, the atmosphere had other plans.

On the way up, early initiation (before 18Z!) yielded a mess of multicellular and occasionally supercellular storms in SW OK, the anvils of which we could see. We chose not to be distracted by those “sucker storms”, and instead forge NWward with steadfast resolve for our target area, where both low-level hodographs and deep-layer shear would be stronger.

Along the way, near Seiling, several deep towers erupted in the free warm sector, seemingly along nothing more robust than faint differential-heating patches. These would glaciate for 10-30 minutes, then dissipate, leaving behind residual anvil shadows and a few souvenir raindrops. The appearance of such midday convection, well-removed from either the dryline and the warm front, dichotomously encouraged us (no problem getting storms today!) and troubled us (too many storms today?).

As we headed N through P28, convection began erupting in a band up and down the dryline from NW-SSW, boosting hope for a targetable storm, since we still were well out of reach for the activity up near I-70. One storm crossing the KS-OK border quickly acquired flying-eagle structure in reflectivity and standout VIL, while darkening the skies to our SW. Although the low-level SRH wasn’t too favorable in the immediate area, thanks to some earlier veering of surface winds ahead of the dryline, the flow was starting to back a little again. We were excited that this could be our target storm, moving NNE then NE into a progressively better environment with time. Too bad several other storms formed in its immediate vicinity, messing up the structure before it got to us.

The most spectacular event of the whole trip then happened in a flash. As we waited just off the NE edge of PTT, a CG from one of the leading cells struck a sheet-metal building across the road from us, instant FLASH-BANG, its white-hot column dispersing into a vertical necklace of brilliantly glowing, golden-orange plasma beads that blew northward in the wind for a second or two before dissipating. What a pyrotechnic display!

Our target storm became entangled in the mess of surrounding convection and lost its structure before reaching PTT; so we targeted a tail-end cell and headed W several miles out of PTT. By the time we met the “anchor” storm, it was but a small, smooth updraft base with a short tail cloud. By the time we found a stopping place for me to take a photo, the updraft cloud column shriveled to a pathetically flimsy chimney, soon to vanish altogether.

Surely this couldn’t be our fate for a day of such promise?

We scrambled NE toward Lyons to intercept a small but intense storm that materialized from the southern portion of the same precip area N of PTT, but it too turned to mush by the time we got there. All that was left: a strand of towers that had no chance to mature before crossing the warm front. Game over.

Here we were just S of Lyons, on the warm front, breathing in some of the most deliciously refreshing, richly moist air a human or storm could ingest, all for naught.

On the return drive from HUT-ICT-OUN, we smacked into an intense gust front just S of the OK/KS border, then stayed in near-severe winds for at least 25 miles across a swath of Kay and Noble Counties. This was an impressive macroburst, one of the most sustained I’ve encountered, blasting northwestward from a SSW-NNE band of high-based showers. Overhead and to the S we could see a patchwork of virga and loose mammatus in the twilight, and also encountered intermittent light rain reaching the ground. The headwinds buffeted us hard, shaking the vehicle some and compelling a little white-knuckle gripping of the steering wheel on Ryan’s part. Dust and grit reduced visibility to less than a mile, making noise like sleet as it bounced off the windshield at times.

We also saw a sporadically splendid display of anvil crawlers and a few CGs from the northern cloud shield of the MCS that was moving across the OKC and Blanchard areas at the time. After retrieving my vehicle at Ryan’s, I went to eastern Norman and attempted some lightning shots ahead of the leading gust front, but nothing too spectacular…I kept missing the brighter and closer CGs before the electrical area got too close to shoot safely.