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.

Software Change for the BLOG

November 4, 2008 by · Comments Off on Software Change for the BLOG
Filed under: announcement 

We interrupt this BLOG for an important announcement. Had this been an actual emergency, you wouldn’t give a flip. But since you’re reading this, here goes…

After several problems with security, poor SPAM filtering for comments and track-backs, slow performance, and general user unfriendliness on my end, we finally flushed Movable Type and switched the entire BLOG to Word-Press.

This includes all the previous entries and underlying database. Word-Press has a different file naming convention, which rendered all links to previous entries invalid. Elke, bless her heart, had to go through and update the links one-by-one, since that didn’t happen automatically. Still, if you happen across an unresponsive link to another BLOG entry, let us know and we’ll fix that.

As for comments, those had been disabled for a long time in MT due to an avalanche of SPAM that MT seemed utterly powerless to restrict. Somewhat regretfully, the only way to exterminate the infestation of digital vermin was to ban all new comments. I may try to open comments for the 2008 chases for awhile and see what happens; so if there’s a chase day for which you want to compare notes, look it up here and comment if possible.

Check out the cool things that happen when you click on a photo link. The image appears in a window that allows forward/backward sequential viewing of the chase day’s slide show. Just run your cursor over the right or left side of a photo and a forward or backward arrow will appear, on which you can click to go backward or forward in that day’s selection of chase photos.

We’re also considering some relatively unobtrusive web ads (at the bottom of the BLOG page) to offset the costs in overhead, as long as I have power of pre-approval over any advertising content. It’s not a done deal, so we shall see…

The “Liberty’s Crown” Storm

August 29, 2008 by · Comments Off on The “Liberty’s Crown” Storm
Filed under: Summary 

…and a Few Other Supercells from KS to the TX Panhandle

20 Jun 8

SHORT: Observed series of HP supercells from SW KS to Pampa TX.
Read more

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