Chattanooga Chase

July 10, 2013 by · Comments Off on Chattanooga Chase
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Chattanooga & Lawton OK
17 Apr 13

SHORT: Intercepted a few supercells in the FDR-FSI corridor, power flashes with one SW FSI and another near FSI, followed by late intercept of Red River storm.


Weather and logistic setup
This day featured a somewhat classical cold-frontal/dryline scenario ahead of a positively tilted middle-upper level trough, and all the geometric funkiness that can impart to winds in the 2-4 km AGL layer. Capping looked strong enough to preclude much dryline development except right near the triple point, which was a little concerning given the direction of the flow aloft bearing a strong component parallel to either the front or a vector drawn downshear from the likely genesis zone. Nonetheless, 0-1 km shear, deep shear, moisture and CAPE all were expected to suffice for supercells in late April in good chase country of SW OK, and I was off duty. That means just one thing: out the door in search of more.

Bryan Smith and his family had a red-eye flight scheduled for the next morning, but that didn’t deter him from wanting to feast on the atmospheric smorgasbord within a couple of hours of home. We left Norman, driving through some driving rain along the way, before fueling in FSI. There we encountered Mike Foster, recently retired from his post as chief of the Norman NWS Forecast Office, who (along with us and seemingly thousands of others) was targeting a new cell that had erupted over the Red River area and slowed down almost directly atop FDR. At least Mike wasn’t chasing on his motorcycle!

Initial FDR-FSI supercell
We used Spotter Network to avoid the heaviest stream of storm-bound dots for the longest time possible, taking some back roads S and W out of Indiahoma to a point a few miles E of FDR (and well ahead of the accumulation of dots). As we waited, the storm slowly came into view sporting a fuzzy but broad base, then a flat and (at best) weakly rotating wall cloud commensurate with a decidedly pronounced d(dot)/dt around our location.

Hey, these days, with all the chasers, pseudo-chasers and wannabe locals congregating around Oklahoma storms, it’s a sad but necessary part of photographically-minded intercept strategy to anticipate storm maturity, movement changes and mesocyclonic cycles, then claim good viewing spots in those potential areas ahead of the hordes, whenever possible. Understanding and anticipating likely storm morphology, motion and behavior is helpful, when dealing with a vast majority who just whack-a-mole chase the spinny screen icon in reactionary mode. It’s a chess game, in a way; and such foresight does reap benefits in the field sometimes. When the storms and the roads don’t make other plans, it can prevent a some stress later. My most consistent trouble instead seems to be picking the “right” storm among several. 🙂

Sustaining rotation aloft was a struggle for this supercell through most of its lifespan, thanks to a combination of those wind weaknesses aloft and upshear cell mergers, but it did manage to wrap up a couple of nice visual low-level mesocyclones. The first was seen from 8 WNW Chattanooga, looking W, as a low-hanging, rotating wall cloud with strong feeder inflow on the NE side. Between that shot and the next one was about as close as a storm can come to producing a tornado, without actually doing so; such was the vigor of cloud-base rotation. It also was transient–precip from both the storm’s own hook and some annoying upshear convection soon wrapped around, undercut and weakened the circulation. Lo…gaze to the dirt-road horizon in the previous photo–there comes a train of dots! It was time to reposition downshear.

Unfortunately, it looked like the storm was going to track right over the W and N sides of Lawton. Warnings were in full effect, covering that scenario. Still, having a city in the way of a potentially tornadic supercell is highly undesirable, most importantly for its citizenry and secondarily for observational strategy. We had a short viewing window from just SW of town, whereupon the storm tried very hard once again to wrap an occlusion and produce a spinup. We’re not sure if it did in this stage, at about 1719 CDT, though a suspicious column (enhanced crop of last image) soon appeared that was either a brief dust tube beneath the center of circulation or a dense precip shaft right behind it. That was a view looking W from Coombs Rd and SW 97th St in rural SW Lawton. Poor contrast precluded visually ascertaining the rotation, if any, of that column.

Just a couple of minutes after we headed back E onto Coombs Rd toward LAW airport, and at about 1725 CDT, a power flash occurred to our NW, while: 1) we were in motion and 2) the mesocyclone took a NNE jog back into the core. I immediately pulled over and shot a few photos, including this one, of the suspicious area from which the flashes came. This was the same part of the storm into which Jared Leighton and Scott Blair filmed power flashes, at about the same time, but in their case, looking WSW from within the developed part of Lawton. Tornado or not, we were certain that damaging wind of some sort was underway inside and beneath the low-level mesocyclone and its ragged, diffuse cloud and precip features.

Soon thereafter, that mesocyclone also got undercut by its own merger-assisted RFD surge. The storm kept tripping over itself! A resulting interlude before the next potential wrap-up gave us a much-needed time span to trudge through the S side of Lawton along OK-7, amidst wailing tornado sirens, then find a short-lived, hilltop vantage about a mile E of I-44. We watched the storm get ill-defined as what was left of the main mesocyclone area moved to our N, decided it was too messy and going into a less favorable environment, and headed fo a newer supercell evident both visually and on radar to our SW, again near FDR. This maneuver took us back down I-44 and W on OK-36–an intersection through which we would pass thrice more!

Second and third FDR-FSI supercells
Visually, as seen from 6 N of Chattanooga, the second storm looked pretty in a ragged way–but also, rather undercut and surfing its own outflow to some extent. This predicament looked familiar, but we kept abeam of the storm in its inflow region, back through the I-44/OK-36 junction and right back to the high spot on OK-7 just E of Lawton.

This time, we watched from a church parking lot across the street, seeing a power flash in the northern fringes of Lawton (or near FSI) at about 1857 CDT. I took a few photos immediately afterward looking back into the mesocyclone area, and they don’t reveal much (even in ridiculous enhancement). Fortunately, Lawton was spared any substantial tornado impact for the second time in less than two hours; though some damaging hail hit the FSI area and the northern fringes of the city.

After watching this storm blow its way off to our N to join the freight train of heavy rain, we headed SW to another apparent supercell on its heels, running back through the I-44/OK-36 intersection again. Darkness was descending, and we only briefly watched this rather messy but still weakly rotating storm follow a very similar path and process to the others. Getting very hungry by now, we jumped a couple of miles back N behind this storm to a Taco Bell for a quick bite.

Grandfield supercell and return home
Pumping cheap quesadilla slices down one’s esophagus isn’t the ideal activity while seeing a raging velocity couplet bust out of the radar screen on another storm to the SW. I damn-near choked. This was a cell that was fixing to cross the Red River between Vernon TX and Grandfield, OK, a storm that apparently was getting very happy with the onset of the low-level jet (and resulting hodograph enlargement). This was easy to forecast; we just let hunger and fatigue get the best of us. In retrospect, we likely wouldn’t have gotten there in time to see either of its tornadoes anyway; but we still tried to see what was left.

Zigzagging S and W past the OK-36 exit and through backroads, some impressive structure was evident in fast-fading twilight. I wish I had stopped to photograph this. Both darkness and intervening low clouds conspired to obscure much of the storm within minutes, as we closed in, ENE of Grandfield. A navigational error of mine took us eastward one section road N of where we thought we were, and we found ourselves ahead of the mesocyclone, in the dark, on what disturbingly became a rough, dead-end pathway through grass. Fortunately, we still had several miles of leeway, and I had a high-clearance 4WD. As such, were able to double back down the section “road”, zip S promptly out of the hook’s projected path, and let the storm slide along to our N. Still, it was a valuable reminder about double-checking one’s positioning.

As for the storm, the mesocyclone area assumed a rather ragged, circular and toothy appearance to our W, NW and N, as seen via lightning flashes and assorted nearby town lights. Cold outflow, felt well SE of the main updraft base, didn’t portend a healthy future for this formerly grand supercell; and it slowly decayed to our E and SE as we cut behind it to head home via US-81 and OK-9. Bryan slept most of the way back—and needed it. We arrived in Norman just before midnight, with Bryan still having to drive up to his place in Edmond and get a few more hours of sleep prior to heading to the airport for that red-eye. I didn’t envy his predicament; but he indeed survives to this day.

Afternoon Towers, Twilight Flashes

May 10, 2013 by · Comments Off on Afternoon Towers, Twilight Flashes
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Seminole & Tecunseh, OK
15 Apr 13

SHORT: Struggling but occasionally photogenic convection near Seminole OK followed by lightning observation on back side of twilight storm complex.

LONG: During the day, a cold front had hung up along a weak frontal-wave low about 40 miles to our SE, closer than previously expected. While driving home from a dental appointment, which followed a day shift at work, two main things were on my mind–the Boston bombing, about which I learned at the dentist, and the towers going up on that boundary, visible to the SE.

Storms were more palatable to contemplate than the other grim issues of the day, so I headed home and picked up Elke for a short trek E. The better environment for photogenic, diurnal supercells was in north-central TX, NW of the Metroplex; but that was too far to reach before dark. We were hoping the cap could break closer to us, along an increasingly well-defined inflection point that lay nearly stationary over the area between Wanette and Konawa. That point also corresponded to the intersection of the frontal zone with a confluence line extending behind it to the NNE, and was persistently focusing the deepest (albeit still cap-dominated) buildups.

This part of Oklahoma is hilly and moderately forested, so high spots with good visibility are rather scant. During the couple hours or so before sunset, we waited at two places along US-377 S of Seminole–one right on the boundary, and another just to its N with better visibility. From the first, we saw one Cb erupt on the inflection point, briefly acquire strong radar reflectivity, then tear off to the NE, along the confluence line but also on the cold side of the boundary.

From the second stop, closer to Seminole, we photographed intervening towers with crepuscular rays, as a newer storm developed to the SW. The second Cb approached, skinny and pockmarked with holes, but beautiful to behold nonetheless. That likewise withered, so we headed into Seminole to grab some fast-food dinner and await further developments.

After supper, we saw a multicellular cluster forming back on the frontal wave and inflection to the SSW, and decided to get on the NW side of it for sunset color. Several cells emerged from that mess, including:

1. a sunset-illuminated left mover W of Tecumseh,
2. a right-moving supercell that we actually blew off because of its positioning on the dark side of the cluster, and
3. another left-mover to our E that was buzzing with a lot of in-cloud lightning discharges. The sky actually was darker than the photo makes it seem, due to the length of the exposures. Still, I wanted to strike that fine balance between bringing out the convective structures while not exposing for too long and blurring cloud features on a fairly quickly moving storm. How quickly?

Since then I’ve created a time lapse of the tripodded lightning shots I was attempting, so that you can gain some appreciation of the beauty of the third cell as it cruised fairly rapidly across the twilight skies to our SE. Please enjoy it. The time lapse spans six minutes, so you can see the fairly fast translation of the storm. Dial the speed meter up to the max level for full effect.

It was a mild, beautiful evening to watch the dynamic sky!

Southwest Oklahoma Classic-HP Supercell

May 16, 2012 by · Comments Off on Southwest Oklahoma Classic-HP Supercell
Filed under: Summary 

Hollis to Apache, OK
13 Apr 12

SHORT: Chase route GCK-LBL-HHF-LTS-OUN. Intercepted occasionally photogenic supercell from inception near Hollis to N of Duke, then as it got absorbed into what became an HP “Stormzilla” NE of LTS that crossed Wichita Mountains. Activity forming SW of that merged/absorbed it after dark N of Apache.

The day before turned into a storm-free “bustola” on the western Kansas dryline, with only distant convection to the north near sunset. Elke and I salvaged something from the 12th by heading to Monument Rocks for the late-afternoon light, then bunked down in GCK.

Today’s most straightforward storm intercept target was over the NW TX, SW OK and SE Panhandle region near CDS. We left GCK for a long but simple jaunt SSE down US-81, with lunch in Perryton. While there, storms already started firing over central and SW OK. Early initiation stinks, especially when the observer still is over 150 miles away!

A distant line of building convection hovered just above the SE horizon as we headed out of Perryton. Now we targeted the area of its prospective backbuilding into the slowly retreating late-afternoon dryline. The pre-dryline baroclinic zone upon which the storms were forming was supposed to retreat N also, after 21Z. My thinking was that the future western storms would represent the latest, highest-CAPE development, farthest removed from the threat of interference by upshear convection.

Given our distance and target area, we obviously missed the Norman tornado, not that we would have targeted specifically that needle-in-haystack HP supercell event anyway. As we reached Wellington, big towers began to backbuild on the pre-dryline boundary toward the Hollis-CDS area; so we turned E on US-63 into SW OK to get into position. We fueled up at Hollis as a young storm began rotating ESE of town, and newer convection with cores formed to our S-SW near Vernon and CDS.

Using phone radar, I noticed a nasty-looking hook had developed on the W side of Norman, with an HP supercell attached to a larger cluster of storms extending westward. It was a mess, but a mess with a meso. I called my daughter, who told me she just had experienced a tornado at the high school and had been safe in a windowless room, under a desk. The first concern, and relief, was that she was fine. My son was elsewhere, well SE of the path. Both were OK, so I could shake my head and marvel at the truth that, once again, a tornado had occurred in Norman with me observing other storms far away.

We cruised E out of Hollis, preliminarily targeting the storm to our ESE, but with a contingency to stop and let the newer development to our SW (then the tail-end conceptual target) come toward us if it started looking good. That’s exactly what happened. CGs from the newly organizing, tail-end convection slammed all around us between Hollis and Duke. We turned N out of Duke, found a good vantage 3 N of Duke, let the disorganizing eastern storm move away to our NE, and watched the newer storm approach and strengthen.

Alas, still more convection formed upshear, but the storm began looking distinctively supercellular as it crossed the section road to our W. This would become the Altus-Apache supercell, but not before producing a nice wall cloud, one with strong rising motion but only modest cyclonic turning. Another lowered area, likely from an older occlusion visible in the last windmill shot, loomed in the background.

Neither got any better organized; indeed, the entire storm started looking somewhat strung-out. We considered breaking off and heading toward the newer activity W of Hollis and W of CDS, as some others already were. However, we needed a pit stop in nearby LTS, while the supercell began turning into a dark, menacing, precip-filled mass to our N. We decided to stay with it for awhile, watching what by now was an HP “Stormzilla” over the western nubs of the Wichita Mountains.

Our supercell developed a nasty-looking HP hook on radar with a deep, intense mesocyclone; but we couldn’t see anything in the dark murk from LTS regarding the tornado report near Blair. Even without the bathroom break, I’m not sure we would have been able to get in position to see much.

By the time we reached Snyder, it was to late to do much with the western convection before dark. We also knew that the storm would head into an awkwardly configured road void in the Wichitas, cutting us off. [I had circumnavigated the void successfully last November 7, but from a different angle. That day, I beat the storm. This day, the storm would beat me.]

Driving several miles N out of Snyder, we hoped to see whatever the storm had to offer before it got into that road void. Here was its S side, along the rear-flank gust front looking W. Here was the E side, looking NNW toward a small but slowly rotating cloud protrusion with a clear slot. That looked interesting for a few minutes, until being undercut by a massive surge of the heavy precip-loaded RFD.

The photogenic HP storm moved off into the road void to our NE, and we knew it would be dark by the time we could get through Lawton and go N toward Apache to see the storm again. The storm produced a rainy twilight tornado during that interval when we were repositioning, fittingly enough.

By the time we reached Apache to see what was left, we found a storm still supercellular but again messy. Our viewing timing with respect to the best-organized stages simply wasn’t working out. At least, for a short time, the downshear anvil region sparked mightily and beautifully overhead. Our last decent wide-angle view of the storm, from a hill just E of town, featured the lights of the wind farm and Apache to our W, what was left of the wall cloud and main updraft region near center (NW), the vault area to the right (NNW), and of course, cows.

Before the storm could cut off itinerary options again, we headed NE toward Chickasha and home. The storm merged with convection to its W, evolving into a small bow, then moving over Chickasha and toward the Purcell/Pauls Valley area a weakening blob of rain and occasional hail. By then, we were home, tired from the two-day, thousand-mile trek, but eagerly anticipating the big severe-weather day of the 14th.

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