2009 Season Opens Early

February 11, 2009 by · Comments Off on 2009 Season Opens Early
Filed under: Summary 

Central OK Supercells, Bow and Lightning
10 Feb 9

On day-2, the best target area appeared to be north TX or the Red River region, based on doubts about the ability of the moist sector to return northward appreciably into OK. Those doubts, in truth, were unfounded. Not only did the 60+ degree surface dew points make it to the Red River, they reached I-40, and the inflection point between the returning moist-sector dew point gradient (also perhaps a weak warm front) and the dryline itself exerted a decisive influence on the events in central OK. When the atmosphere amends your forecast for you, you must be flexible enough to adapt your target area and strategy! I adapted northward 160 miles, but in hindsight, 15 more miles would have worked out best.

After joining Bryan Smith at Battlestar Norman around noontime, we watched the bend-o-the-boomerang leap northward with astonishing speed from the Nocona/Bowie area to west of Norman, whereupon two storms quickly formed and cruised NNE, then NE. Bryan, his wife Carolyn and I headed W then NW to Mustang, with the idea of sampling some of this “early stuff” before catching the “good stuff” farther S, in what we thought was better air, later. Then came the tornado warning and reports for the storm to our NNW and N, just out of reach. We were unwilling to stern chase it through a metro area, but briefly glimpsed some lowerings in the distant N, under the updraft region and through the murk.

Our concentration turned to the next storm headed our way. A couple miles back S of Mustang, we watched it cruise by to the W while experiencing bone-chilling cold temps of 55-59 deg F in the rainy easterlies. The inflow air, left behind by the Edmond storm and rained into from heavy anvil above, felt like the breath of the Abominable Snowman, and our storm looked the part. That storm roared past, and we headed down to just SW of Tuttle to watch the “Anadarko” storm cruise toward some point a few miles to the W. It had more interesting banded structures aloft, and a rather large base. The inflow temps were in the upper 50s at this point, and we weren’t optimistic of its chances to ingest better surface air. As the storm repositioned itself to our NNW, and the inflow veered to SSE and S, temps jumped into the 60s, and low level structure improved dramatically (17 mm wide angle and super-enhanced crop), with a clear slot and narrow, short-lived, nearly ground-scraping lowering. That lowering didn’t appear to rotate much, if at all, and soon became somewhat clunky looking and scuddy. Nonetheless, any storm that looks like this deserves some scrutiny, especially when nothing else farther S shows much promise, and an earlier storm along much the same track produced a hose.

So much for hesitation to chase through the OKC area. With this storm being the only thing going that was worth tracking, we wheeled up OK-152, I-44 and I-35, watching ragged wall clouds come and go, and hitting much colder air N of Edmond (back into mid-upper 50s F). This was our last view of the storm, from the SSE, with a sfc temp of 55 F, between Edmond and Guthrie. It looks like a ground-scraping wall cloud, and maybe it was, but a lot of that looked to be an artifice of high RH in cold temps (a.k.a. rain and hail fog the updraft was ingesting).

Ryan called to inform us that nothing of great importance was happening within daylight’s reach, and(as we suspected) the activity to our SW had gone linear. Phooey on that! Bryan’s head was spinning by now, given that he had worked a 12-hour overnight shift and had been awake all day since, so I dropped him and Carolyn off at NWC he could get some long overdue sleep. On the way down I-35 from OKC, we could see a small tower try to develop just S of Norman (and ultimately fail), as well as a deeper Cb with overshoot in the very distant S, which became the tornadic Lone Grove storm after dark.

With a well-developed bow echo now charging NE toward Norman, I shot a quick dark-storm-looming scene looking SW over the facility, then picked up Elke and the kids at home. We headed over to the mysterious and legendary Tower of Doom (TM) to take RJ up on his invitation to watch the show roll past, capturing a few aerial lightning filaments looking W under the gust front and looking E into the trailing precip.

Sure, we didn’t experience the rush of excitement of those who were fortunate and willing enough to brave the urban storm intercept earlier. But this, remember, is February. To have a couple of rotating storms, a bow echo and some lightning cinched 10 days after January means the 2009 season is off to a mighty fine start. This was a way to “tune up” for the meat of the season in another couple of months, but perhaps more importantly, a soothing atmospheric poultice, applied to an accumulated ache of yearning built over months of frigid deprivation, for the unrivaled amalgam of brute force, sinuous dynamism and imposing beauty that is the supercell.

Four Supercells Seen from One Spot

November 7, 2008 by · Comments Off on Four Supercells Seen from One Spot
Filed under: Forecast, Summary 

Who Needs to Chase?
5 November 8

Even though I was committed by shift work to being at NWC through the evening hours, there wasn’t any pressing need to chase today to see supercells anyway. All I had to do was pay some intermittent attention to what was going on outside, watch them race by, and run out for a minute or two a few times to observe.

After several storms formed ahead of the west-central OK dryline, and in a narrow plume of favorably heated and moist boundary layer air, a visual treat ensued, which I was able to document in a few quick breaks from the priority of duty.

The first visible supercell moved past me well to the NW (Piedmont/OKC storm) as I drove in, but the sky was clean, and the base could be seen way off in the distance (sorry, no photos). I did see a ragged, scuddy wall cloud just above the horizon before losing sight of the storm. The next supercell moved NE from the CHK area over the W and NW part of Norman, exhibiting classical (if somewhat messy) structure in a wide-angle view, looking W. A zoom view shows a ragged, partly rain-wrapped wall cloud (strongly enhanced image), which showed (at best) very weak cloud-base turning. Upward motion of scud was rather slow too. Still, this storm was a well-defined supercell, visually and on radar, and and dumped a large amount of severe hail in a swath across the NW side of town. The mesocyclone area below cloud base soon became outflow contaminated, a process becoming evident in this view looking NNW.

A second, weaker supercell formed SSW of town, its forward-flank core heading right for us. A left-split updraft tried to calve off the forward (NW) flank of the storm (view looking SW), but didn’t last too long. The back side of the main storm, which passed over E Norman, caught direct and indirect light from the setting sun, and glowed almost otherworldly in pastel hues, making an uncommonly and delightfully tinted scene above the fall colors of local trees. The view in the last shot looks SE, which means that the light was reflected from the storm, casting unusual shadows and light angles for this time of day. Notice that the brightest light is on the left (NE) side of the trees!

The towers responsible for that reflection loom above a mostly silhouetted structure of “Battlestar Norman” in this view, looking ENE from the adjacent lawn. As the sun angle fell further, the hues warmed for just a few minutes (seen here looking ENE from the N side of the building). Even as the reflected solar glow faded, the hues of twilight kept the scene beautiful (wide angle, looking E). Not bad for November, eh?

That wasn’t all. A short while later, Ryan came in to request photography of a feature that looked a lot like a midlevel funnel, apparently sticking sideways (southward) from a convective deck to our WSW (crop-n-zoom on the feature). It was hard to tell if that really was a sideways, midlevel funnel or just a visual juxtaposition of two separated clouds. You make the call.

A well-defined left split peeled off another supercell (unseen) to our S. The anticyclonic supercell raced by us to the W, in the fading twilight, also leaving a swath of hail from the small but pronounced core on its S side. This is a mirror image of the left split showing classic skeletal structure, albeit high-based.

As for the broader event, as a whole and outside the line of sight from the NWC ground floor, it was resoundingly unproductive for tornadoes. All we had were a few cheesy tornado reports long after dark and outside of the 15%_SigTor (MDT) outlook area. What went wrong? My during-and-after interpretation of eyewitness observation, surface maps, soundings and radar inferences was that a blend of storm-scale and boundary layer thermodynamic failures was at least partly responsible. The storms were somewhat high based and spewing a good deal of cold outflow (as well as hail). Mesocyclonic occlusions and transitions to (cold) rain-wrapped states occurred quickly, resulting in insufficient time for circulations to form and wrap up tightly. Supercellular structures did improve during the sunset/twilight periods; but unlike in more moist events, MLCINH also ramped up quickly with enough surface T-Td spread to foment an unfavorable amount of cooling. Discrete supercells — by then E of I-35 — responded by shriveling away as they headed into the jungles of eastern OK.

What might this event have done had the dew points been 5 deg F higher? John H and I speculated on shift that we would have had a more buoyant and temporally longer lasting surface-based effective inflow layer, the better to take advantage of the enlarged hodographs beneath the early evening strengthening of the LLJ, and perhaps a bonafide multi-tornado event in that case. The citizenry of NW Norman should be glad for those lower dew points. Had that storm been tornadic, while still takin the same path (an unlikely thing, admittedly, given the forcing that differing storm-scale processes can exert on a storm’s motion) the path would have gone through some newly (last 10-15 years) developed parts of town W of I-35 and N of Robinson.

We see one sig-hail report from the Piedmont area storm (Rancho Rascovich being a supercell attractor of the highest order). The NW Norman supercell did dump a lot of hail up to nearly 2 inches diameter on several neighborhoods, busting windows and/or skylights in many homes where accompanied by estimated severe gusts, with glass breakage at the homes of several colleagues and co-workers who live in NW Norman. Elke encountered some falling hail ~1.5 inch diameter near and N of the YMCA (north base area) from a small core after dark, near the cold front.