Sampling the Gust Front

May 18, 2009 by · Comments Off on Sampling the Gust Front
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South-central KS and north-central OK
15 May 9

SHORT: Early supercellular structures then linear and outflow-driven complex observed.

LONG:
Once again we found ourselves headed generally NNW on a storm day with marginal midlevel winds likely to be dominated by frontal forcing, but with a weaker cap than on the 13th. Cu already were bubbling near the front/dryline intersection in the northeast TX Panhandle, but time spent analyzing the situation was too much to head that way. Too bad too; since a nice, tornadic HP supercell roamed those parts within another couple hours. Instead we decided to head N up I-35 to at least US-412 with the option of going W toward northwest OK or N into south KS, depending on convective trends.

Nothing had formed but the Panhandle storm and some cells well to our NNE in the Flint Hills by the time we got to the border, but it was obvious from visible satellite imagery that discrete linear backbuilding would commence very soon. By the time we rounded the corner westward at ICT, the anchor point for the frontal line was near Kingman, and by the time we got to Kingman, it was still farther WSW.

Still, we found two rotating updraft regions in very close proximity to each other, between Kingman and Harper. Looking NW, the northern member was small and shriveling further, but spitting numerous CGs from the NE fringe of its tilted updraft area. Looking WSW, the southern storm looked bigger and more robust, albeit somewhat high-based, but was about to be rammed unceremoniously by storms just upshear in the line. We dropped S and let that storm pass to our N and NE, whereupon it cleaved itself with an RFD cut and shrank into oblivion.

The rest of the afternoon was spent zig-zagging S and E to stay ahead of the massive outflow pool that had begun to build a long shelf cloud (here seen behind cornflowers just S of Anthony KS, as backdrop for a deployed sticknet unit about 13 W of Medford OK, and sheltering a CG 1 W of the OK-11/I-35 junction). For awhile between Manchester OK and Anthony KS, the anvil shield painted itself with numerous little streaks and puffs of mammatus, as if barnacles on the underbelly of an old oceangoing freighter. Occasionally a mobile mesonet or radar affiliated with V.O.R.T.EX.-2 would be seen, but the various field project vehicles seemed well dispersed.

The shelf cloud overtook us for awhile on I-35, occasionally stretching tubes of dust from distant (and non-tornadic) gustnadoes up toward scuddy fingers protruding from the lip of the shelf cloud. We did briefly stop on the S side of Perry to admire the strikingly sharp and clumpy textures of the shelf’s underbelly, which glowed with a dark and eerie slate-blue hue thanks to the heavy shadowing above, dense and light-absorbing core aft, and southern influx of late-day illumination from beyond the bow.

We got out from beneath that complex N of OKC, and ate a late dinner at the Cracker Barrel in Norman as that complex threatened to merge with a bow echo from the W. The gust fronts did come together over Norman, but with little fanfare save some cool breezes and a little over an inch of rain lasting past midnight. So ended our first (shorter) chase break of 2009, as a terrible western ridge and deep eastern trough pattern set in.

Storm Observing with the Next Generation

May 10, 2009 by · 3 Comments
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Ardmore OK area
8 May 9

SHORT: Messy supercell viewed through hazy skies near Springer, followed after dinner by nice nocturnal lightning show at Lake Murray.

LONG:

Since it was likely to be a hot, humid and hazy time in the inflow, with very slim hope for crisply visible structure or a tornado, Elke wanted to stay home and get some work done. Figuring that the strong cap would delay storm initiation along the front until late in the afternoon, only about an hour’s drive away, I instead waited for my two storm-observing teenagers, David and Donna, to get out of school to take them on a little country drive to a southern OK atmospheric laboratory.

After passing through the cold front near Pauls Valley, we waited for storm initiation at the southern “scenic overlook” N of Springer, passing the time with assorted conversations, testing the “Shazam” song app for my I-phone, and admiting assorted wildflowers, some of which were quite popular with local honeybees.

Some towers to the SE, ahead of the front, tried…but aborted. Finally, sharper, deeper towers became visible to our W, through the haze of Mexican biomass incineration.

Figuring that real storm genesis was imminent, given frontal lift and huge CAPE, I headed the several miles down to the NW side of Ardmore to top off the petrol supply. As we left the fuel station, two primary storms became evident, both on radar and visually: one near Loco, the other near Hennepin (W edge of the Arbuckles). Both were within easy reach. The northern storm was getting better developed faster, but the southern one was not far away and surely would rain into the bigger storm’s inflow.

We headed W off the Springer exit, past Woodford and Milo, and waited for the Arbuckles storm to become deviant and turn SE out of the road void. One distant wall cloud was getting more ragged as we approached and stopped. As the storm got closer to us (near Milo), another wall cloud got better developed (24 mm wide angle) with a long plume of scud racing inward (leftward). The low levels of the storm sported vigorous convergence but only weak rotation. Even though plenty of anvil rain fell upon us from the Healdton storm, the thermometer measured 77-80 deg F in the precip. It seemed to be boosting RH and lowering LCL. The anvil rain also seemed to have just a little negative impact on buoyancy, but not too much to suffocate the storm until after dark, when it merged with the forward left flank of an expanding HP storm to the SW. As the HP storm grew and slogged over the S side of Ardmore, we called it a night and ate dinner at the Flying J truck stop buffet.

When we left the truck stop, the light show was amazing off to our SSE-SE, on the back side of the supercell that was moving across Lake Texoma toward Sherman. Continuous in-cloud strobing and occasional visible filaments kept the sky and ground well-lit. We cruised down to the NW corner of Lake Murray in hopes of getting some lightning shots looking across the lake. The storm, still buzzing constantly with IC lightning, was a poor producer of visible CGs on the back side, but it did provide one nice shot with some mammatus visible. The tan-orange color on the water and cattails is from the parking lot lights for the boat ramp we used.

As we watched the supercell recede into the distance, an elevated storm erupted to our N and quickly moved E, flinging the flashing forks of Zeus off the edge of its core every 3-4 minutes, with considerably thunderous fanfare. I tried to time the cycles, missing a couple of good ones but capturing a few others. You wouldn’t want to be a boater out on the lake, far from dock, and see this from a storm moving your way! Fortunately, nobody was boating, and the storm was moving away from us on the shore. We heard a pair of Canada geese honking from somewhere not far across the water; but it wasn’t until after offloading the photos did I see where they were (lower right, on rock). As the storm retreated, I got one last pair of bolts before rain from another elevated storm (which was moving our way) compelled us to exit the area and head home.

Our return to Norman took us around the back side of the northernmost of the elevated storms, between Noble and Purcell, its rain still falling upon us with nothing but stars and thin wisps of scud overhead, the full glow of the full moon to our S. A fine evening of dad-kid time came to a close, good times shared, neat storms witnessed and memories made. Whatever these kids go on to do in life, they can draw from the experiences of this and other storm observing trips throughout their childhood. These recollections will remind them not only of good times with Dad and amazing sights in the sky, but the capability of any given excursion to provide moments of awe and windows of wonder into the timeless beauty of amazing phenomena that are explained nicely if imperfectly by human science, but crafted completely and without flaw by God, who is the ultimate author of all discoveries that science makes.

My wish for Donna and David is the fullest possible appreciation of such surroundings. From that standpoint, trips like these are gifts that do keep giving. In a materialistic, narcissistic, shortsighted and hedonistic world, it’s better to give a kid experiences than stuff. After all, you can’t take a Game Boy with you when you die.

Storm Structure and Lightning Extravaganza in Western Oklahoma

April 13, 2008 by · Comments Off on Storm Structure and Lightning Extravaganza in Western Oklahoma
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Corn to Rocky to Gotebo to Anadarko OK,
30 Mar 2008

My storm observing comrades on this day were Melissa Hurlbut and Jason Levit. A protracted period of target indecision on my part continued well into the afternoon hours, even after Jason arrived at my place around 3 p.m. Two interesting areas presented themselves in the various mesoanalytic clues:

1. The western part of north-central OK, Woodward-Enid, near a cold front/warm front intersection and near and dear to my longstanding triple-point bias. I liked the shear up there, both in low levels and through aq deep layer, but surface-based buoyancy would be limited, and the warm frontal zone had a NNW-SSE alignment that was too perpendicular to the prospective mean flow and supercell motion vectors for my tastes.

2. A more nebulous but also more unstable zone near the dryline, over SW Oklahoma, where precise foci for forcing in the low levels would be rather diffuse, but where any storms that could form would have hours of room to roam in rotational enrapturement.

After picking up Melissa, we leaned toward the southwestern option, but decided to head out I-40 (via the Newcastle-Mustang bypass) in case some profound clue emerged in the interim that would change our minds. Jason hadn’t been out on a storm intercept mission since 2004; and this would be Melissa’s first since moving to Oklahoma (she previously had chased on Paul Sirvatka’s 2007 COD expedition to Old Mexico, among other trips).

A profound sense of responsibility silently inundated me: the need — truly, the requirement — to rush these faultless sufferers of supercellular deprivation straight to the smorgasbord of atmospheric violence, without further ado.

Mission accomplished, with a rare and stunning ease…

Towering Cu liberally festooned the warm frontal zone between Newcastle, Mustang and I-40, an encouraging sign. We cruised W along I-40 at a brisk pace, further encouraged by an increasingly dense and deep clump of towering Cu that Jason noted on I-Phone satellite imagery, just ahead of the dryline. As we approached Weatherford, we could see the agitated area to our SW-WSW, including a turkey tower and one nascent Cb. Turning S out of Weatherford toward Corn, the towers rocketed skyward and glaciated, forming a skinny but robust storm just to our WSW, seemingly on cue, as if the whole process had awaited our arrival. The appetizer was served, and we dined with gusto. We parked about 3 E Corn for over half an hour with a fine view of this storm, watching an absolutely classical, textbook storm splitting process to our W. The left mover peeled off to its NNE and our NW, while the right mover (christened “Jorge” by Melissa, in fine hurricane naming tradition) headed ENE toward us.

We jogged S a few miles to get out of anvil rain, to watch our western storm “Jorge” for at least a little while, and to get a better view of another growing Cb farther SW (wide angle view of both storms). Jorge was spinning cyclonically, but without much vigor, and exhibited a rather small, high base. Meanwhile, the distant base of the newer storm grew large and began to develop a pronounced wall cloud with suspicious lowerings, whereupon Melissa decided it was worth a name and asked me to take the honors. “Fabio” it was. Comparing the two storms, we decided the southern one had a better future, so we zigzagged past the S side of Jorge and headed toward Cordell and an encounter with Fabio. As we drove past Jorge for the last time, E of Cordell, it grew a larger but still high base, while Fabio obviously and rapidly had become a cyclic, right-moving anchor supercell — the main course on our convective feast.

Intercepting Fabio in this fantastic and traditional storm chase country, with such outstanding openness, road options and visibility, was a piece of cake. Steady, manageable storm motions and skeletal structure certainly helped! We cruised S out of Cordell on US-183 through Rocky, driving through a little anvil rain and melted/melting hail, then wheeled into a viewing spot just S of Rocky. Storm structure looked great — a striated, squat cylinder just to our W with a pronounced hail shaft streaming off the vault region to the NW. The upper reaches of the hail shaft streamed high aloft, nearly overhead, arching slightly north, and the updraft’s spinning stack of tires plodded along right toward us. We knew we couldn’t linger for long; indeed, a smattering of .75-.9 inch hail and the promise of even larger ice balls soon sent us along our way. By this time, Jason and Melissa already were exquisitely pleased with the offerings from the smorgasbord, but the feast was far from finished.

We turned E on OK-9 and stopped a couple of times between HBR and Gotebo so we could observe this increasingly spectacular supercell to our WNW, including a marvelous, sculpted storm and sunset scene and postcrepuscular rays behind us. In the fading twilight, Fabio whirled onward across western Oklahoma, at times looking something like a pair of horizontal flywheels with intermittent wall clouds and RFD cuts beneath.

I wasn’t concerned about tornado development before dark given the high base and lack of visibly tight low level rotation, but had increasing confidence Fabio would survive after dark and have a chance to get really mean once it latched onto the low level jet and drew in an air mass characterized by increases in both relative humidity and mixing ratio. Meanwhile, we had seen occasional chase vehicles here and there, but the lack of more dense crowds was a pleasant surprise. I guess the profusion of paved road options, and of unpaved section roads for viewing away from the highway, helped to disperse the storm chase hordes enough that they were hardly noticeable.

Fabio kept swirling on into the evening, and we kept the storm abeam to port through Gotebo and along the first few miles of the bypass road N-NE of town (the same road alternative that Rich, Jim and I found 28 days earlier) parallel to the closed section of Highway 9. We stopped for awhile to let Fabio move to the NE, where lightning could silhouette its features. Meanwhile, we started to make out a storm to the NW that also was developing supercell characteristics, both visually and on radar imagery that Jason was downloading into his phone. This time the naming rights would belong to Jason — Rico it was.

The new storm appeared to attach itself to Fabio’s rear flank outflow (a very disgusting and repulsive thing if these were people and not storms), and moved very deviantly rightward for awhile toward the SE until it was lined up alomst E-W with Fabio. These two storms would move E in tandem for an hour or so, then interact in a Fujiwara dance, with Fabio ejecting quickly N then NW around the forward flank of Rico. Although tornado warnings and one report came in from about 15 miles to our N, we decided not to risk plunging into the murk and perhaps being cut off along state roads 152 or 37 eastbound.

Instead, we pulled into a high spot E of Anadarko that I had used before, with a commanding view of the amazing electrical show now underway to our N. So-called “anvil zits” — zippy little filaments that zap hither and yon across supercells’ inner anvils — lit up the sky with astonishing frequency, at least one per second. I’ve seen many supercells at night, some of which left me spellbound at their electrical prowess. While a very few have matched the dazzling profusion and frequency of the middle-upper level discharges that Rico and Fabio were spewing in tandem, none have exceeded them, ever in my experience. Capturing them in photographs was laughably easy! See this photo or this one or this one, all looking NE, or this shot looking NNW? I took dozens more similar to those; and I kid you not, I possibly could have had hundreds. This was easier than shooting fish in a barrel, despite the strong and very gusty inflow winds that made me press my weight downward against the tripod to steady it, and yet, still find wiggles on the lights in several of the longer (10-11 sec) exposures.

After filling up my memory card, then culling out a couple dozen “lesser” but still good lightning shots, then filling it up once again, I noticed we all were getting tired, and didn’t bother to swap out cards. We enjoyed the lightning extravaganza for its own sake for a few more minutes, then called it a day and headed the short distance back to Norman, content with one of the best nontornadic storm intercepts to grace these parts in a long time.

Great company, great storms…ain’t that what makes a great chase? That it was.

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