Sampling the Gust Front
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.
Daytime Mild, Evening Wild
Hennessey to Anadarko and Norman
13 May 9
SHORT: Observed multicells and supercells before dark from W of Hennessey to SW of Calumet. Witnessed Gracemont-Anadarko night supercell and power flashes from tornado and RFD winds. Observed part of separate supercell E of Norman after earlier tornado.
LONG: Given the very strong capping that was forecast, and the increasing uncertainty of diurnal storm initiation with southward extent, Elke and I targeted a conceptual zone just NE of the projected “anchor area” of a front-dryline intersection zone. The plan was to grab storms discretely backbuilding SW down the front and watch them in stair-step fashion, until either they lined out or became less interesting than newer development. Once, again, confidence in cap strength gave us the luxury of a late lunch in Norman, before we headed up to Kingfisher. Storms fired to our NNE near the KS border (one of them being the briefly tornadic event that Joel and Blufie captured on the way W from TUL…great work, dudes!). We briefly considered that activity, but turned our attention to newer cells visibly erupting into the sky over Major County, NW of town.
When we arrived at a decent viewing spot between Hennessey and Okeene, the bases looked rather flat and linear, as if frontally forced; but the then-anchor storm got better organized, with a nice anvil push with mammatus, and some tail cloud development off the NE side. ESE storm movement and CGs chased us from the spot. We headed S — coincidentally on the same paved back road W and SW of Hennessey from which we photographed a spectacularly unplanned “planned burn” earlier this season. Other smaller cells started to develop farther SW, merging into the complex, and contributing to a hard net right turn and SSE motion that had us zig-zagging on some paved, but at times quite rough, unmarked roads from Kingfisher SW to Calumet, keeping within viewing distance of the storms now pounding areas around Watonga and Geary.
The daylight was getting short and the low-level jet began to crank up, so we had some hope for more convincing supercellular structure. After exiting Calumet, those hopes came to fruition. On the NE side of the newer cluster of storms to our W (the same one under which Kiel O and KMan observed the landspout up close), a bonafide supercell formed and quickly developed a very low-hanging, slowly rotating wall cloud (wide angle and zoom).
We headed over I-40 S of Calumet, faced with either a 32-mile detour E, S then W on good roads, but with little daylight left, or 4 miles of thinly graveled dirt road leading to to an unmarked paved byway headed S toward Cogar with a bridge over the Canadian River. I chose the latter; and the “crappy” road actually was friendlier to my car than the many more miles of paved but horrendously maintained trash we had been traversing between Loyal and Calumet.
Meanwhile, the wall cloud had gotten undercut, but the broader storm began to acquire striations, and assumed a more circular appearance. In the fading twilight, we could make out a more sharply banded, “stacked plates” appearance to the storm while rounding the corner from Cogar to Gracemont, staying just ahead of its hard southward charge.
Here comes some meteorological discussion for the unitiated to skip, if compelled. I figured this laminarity was related to the balance between the storm’s improving organization and the strengthening of both capping and environmental low-level shear. A mixed-layer lifted sounding curve was “capped” in a pure parcel theory sense, and growing more so all the time through gradual diabatic cooling of the near-surface layer. Despite that apparent handicap, the supercell’s strengthening deep mesocyclone and vertical pressure gradient force caused deep ascent of parcels from the boundary layer through the environmental capping inversion. Effective lifted parcels still were bringing near-70 degree dew point air from the surface into this storm, while the LCL was lowering due to cooling temperatures and loss of deep boundary layer mixing. The strong inversion also was keeping the storm cluster rather isolated from a few others farther NE along the front, so it had no “outside competition” or impediment whatsoever for high theta-e source parcels, other than being able to maintain its own inflow-outflow balance. Storm-relative inflow was quite favorable, thanks to the supercell’s deviant SSE to S motion right into the intensifying low-level jet, which also was enlarging the 0-1 KM AGL hodograph and storm-relative helicity quite a bit. As long as the storm could forcibly inhale surface-based air in this window of opportunity (before either losing access to the boundary layer or evolving into a bow echo), it could survive, thrive and perhaps get really dangerous.
OK, that was the end of most of the jargon…
I described all that because it seems to fit a pattern we often see precede tornadoes with very late afternoon supercells that seem rather unproductive by day, then go berserk at or just after dusk. This one did!
I tried to find a vantage between Gracemont and Anadarko to watch the storm coming in from the N. It’s a good thing we didn’t succeed. Instead we turned E out of Anadarko toward a favorite viewing spot of mine — a service driveway for a hilltop broadcast mast located exactly 6 miles E of town, off the N side of Highway 9.
We parked on the big signal hill watching and photographing that (by then) spectacularly sculpted supercell move in, illuminated by lightning. While we were still parked but packing up, and right before the power flashes started, Elke saw some sort of conical downward protuberance to the near right (N) of the eventual location of the flashes, to our W, silhouetted by faint lightning flashes.
Unfortunately, my still camera had been pointed 90 degrees the other way, northward toward that great structure on the storm’s E side and occasional CGs blasting through the vault region. The last shot was three minutes before the Gracemont-Anadarko tornado became indirectly apparent to the W, off the left side of the image.
We had to bail due to encroaching CG activity (that was my widest wide-angle!); otherwise I might have had a photo of a night tornado — or at least, wheeled the tripod head around for to capture its effect of snapping utility lines. As we were pulling out of our parking place, we saw around a dozen bright power flashes in several different spots ~6 miles to the W, within a 3 minute span…in or very near the N side of Anadarko. The flashes appeared to be buried in thick precip, but were quite vivid, displaying a variety of coloration — some blue, some green, some in between, even a couple with reddish and yellow tinges.
Unfortunately, damage obviously was occurring, but we failed in our attempts to report it in real time. Elke wasn’t getting any traffic on her pre-programmed HAM frequencies. [Turns out the net control operator was sustaining damage to his own business there in Anadarko.] I tried to call the 1-800 numbers I had for the WFO but instead got either a recorded message asking me to call a different 1-800 number to “chat with friends nationwide” (for one number) or rapid busy signals (for the other). [I’ve since gotten updated contact info…thanks Rick for responding so fast!] We then lost all cell signals until we got to the S side of Chickasha, which is very unusual. Finally, somewhere S of CHK on US-81, I was able to call work and ask them to relay the delayed report of the power flashes to the WFO.
We then heard the tornado warnings close to home in Cleveland County, abandoned our (by now) outflow-dominant HP monster SW of Chickasha, and made a beeline back to Norman. We arrived after its weak tornado near Stanley Draper Lake. From Highway 9 east, not far from our house (!), we saw a ragged wall cloud moving SE across the Lake Thunderbird area before it got lost in precip and distance. The lightning show on the back side of the supercell’s HP hook was continuous and dazzling, but mainly in-core. I did capture a few CGs (like this one) looking out my east facing, second-floor window at home.
Based on WFO Norman’s damage survey the next day, an RFD caused most of the damage in Anadarko; but a significant (EF-2) tornado did track from Gracemont southward into parts of Anadarko. This probably was the conical lowering Elke saw right before the power flashes. Here was that part of the WFO report:
-
TORNADO – CADDO COUNTY – NEAR GRACEMONT TO ANADARKO
922PM-940PM
THIS TORNADO LIKELY DEVELOPED NEAR GRACEMONT AND MOVED SOUTH ALONG
AND JUST EAST OF HIGHWAY 8. THE MOST SIGNIFICANT DAMAGE WAS NOTED
ALONG COUNTRY CLUB ROAD IN ANADARKO WHERE SEVERAL HOMES HAD
SIGNIFICANT DAMAGE. THE PRELIMINARY RATING FOR THIS TORNADO IS
EF2…ALTHOUGH THIS IS SUBJECT TO CHANGE PENDING FURTHER REVIEW OF
DATA. MOST OF THE DAMAGE IN ANADARKO WAS LIKELY THE RESULT OF
STRAIGHT LINE WINDS ASSOCIATED WITH A LARGE REAR FLANK DOWNDRAFT.
Since we were perpendicular to (east of) both the tornado and RFD tracks, I don’t know how many of the flashes were tornadic in origin, and how many were caused by RFD wind. The power flashes illuminated dense precip, and were rain-wrapped. It was sobering and sad to know that people were in danger, unable to communicate about it, and only hoping nobody would get killed or hurt seriously. I’m glad and pleasantly surprised that the Anadarko tornado/RFD damage event didn’t.
Colorful Stormy Skies, Day and Night
Southeast Panhandle of TX
12 May 9
SHORT: Mostly multicellular storms observed from Matador to Memphis TX by day, yielding fantastic sunset scenes, then a brilliant and long-lived electrical display after dark.
LONG: My forecast target was the Caprock area somewhere near its prospective intersection wit the warm front, which looked most likely to be along or just S of the latitude if CDS, and N of the latitude of LBB. I wasn’t expecting raging supercells given the weak effective shear and lack of more robust midlevel winds; but I thought we at least had the possibility for brief ones. The very stout cap was a huge concern too, so I also was hoping for a little dollop of good ole Panhandle Magic (As Bobby P has been wont to say, “It’s May, it’s the Panhandle…chase!”).
Elke and I left Norman after a rather late lunch, confident that the capping would hold off initiation in that area until after 1700 CDT. It doesn’t always happen; so I love it when a forecast comes together.
Along the way, we stopped to photograph some abandoned structures, walls constructed of native Cambrian granite cobbles that basked in muted sunlight, surrounded by wheat fields, with the backdrop of the Wichita Mountains for texture. I didn’t stay long to appreciate the scene or do more close-up photography, though. Despite the mid-afternoon sun and stiff breeze, dozens of fat and ravenous mosquitoes swarmed me with a speedy and bloodthirsty attack every bit the equal of their notorious cousins in the Everglades or the Minnesota North Woods.
By the time we approached from the E, as if on cue, turkey towers started bubbling over Turkey TX. Although these attempts didn’t survive, thicker clumps of towers did to their SSW, in Motley County (see towers and flowers). Consider the cap broken! We hung out at some picnic tables in Matador for at least half an hour, eating Allsups burritos, watching assorted other chase vehicles pass through, and waiting for the rather messy, multicellular convection to become better organized. It did, but in a linear sense, and began to accelerate NE toward the CDS-Memphis area.
Off we went the same way, passing right by the same Stitch Ranch entrance that Rich and I used as a staging point for observing the April 29 eastern supercell. Nearby, I stopped to photograph a thick, partly rain-diffused shaft of sunlight beaming through a cloud gap and onto the distant rolling prairie, an orphan of brilliance amidst the stormy shadows.
The messy structures continued until shortly before sunset, when Elke and I decided to move from front to back side of the complex for photographic reasons. We grabbed a quick dinner in Memphis then headed E on TX-256, past some other chasers, to a pleasantly lonely, gravel side road near the Hall/Childress county line.
What a marvelous setting! Warm tones of the low sun painted a brilliant rainbow segment across the deeply bronzed west wall of the storms. The freshly soaked ground gave off that earthy, moist aroma of a formerly dry land newly satisfied. Bird calls of all kinds carried across the cool breezes. Two bobwhite quail carried on a conversation past us as we admired the fiery sunset scene in the western sky; while in the south, varyingly colored low clouds drifted before a canvas of a higher deck with a different hue still (wide angle and somewhat later).
There’s no experience quite like a Great Plains sunset right behind storms. I hope those photos convey at least a small measure of that.
Then came a dazzling display of atmospheric electricity on the back side of the complex, from the southeast Panhandle all the way across southwest Oklahoma and back to Norman. Lightning filaments raced through a mammatus canopy that spread upshear of the complex, giving many storm observers (from us to the V.O.R.T.EX.-2 crews in CDS) a memorable show. We stopped near the TX/OK border to shoot a little of the action, with Elke capturing one of the most crisply defined sets of nighttime mammatus I’ve seen in a photo. This nearly daylight-bright discharge spread overhead and beyond, raising a distinctive, simultaneous crackling noise in some nearby high-voltage power lines. We soon headed home, content to watch occasional flares of electrical brilliance across the rainy night sky.