May 18, 2017

Team Turtle (Skip and Jenn) Forecast:

“Turtle is in Dodge City for the night. We found better options for dinner and lodging here and wanted to mosey a little closer to where the triple point was forecast to be. I'm a sucker for that triple point play. Would love to see a storm fire just sw of town and track toward the warm front as it lifts north. Best shear and instability combos seem like they're right around here in south central KS. I don't see much reason to drop down the dryline into OK. Lid strength index shows the cap opening rapidly between 18z and 21z with the 500s already in place so we should see fairly early initiation again. Early to mid afternoon. I'm hoping that a cell tracking to the warm front will be able to produce early on, rather than us having to wait for a more broad warm sector environment to improve with the LLJ ramping up and other diurnal effects like on Tuesday. We'll hold here until the group can hone in on a target in the morning, but I think we're all sitting pretty.”

Team Woodchuck (Anton and Tracie) Forecast:

“Thanks Turtle. The overall setup today is rather frightening, and by far the best seen during our project activities so far. Having spent the past couple of nights in Great Bend, I have this uneasiness last felt when Tracie, Tim and I hung out in El Reno awaiting convective initiation 4 years ago. Possibly the chilly pre-frontal air will hang tight here today and save them some misery, but for later today things are looking rather devastating for south and central Kansas. Team Woodchuck should be on the road before 9 am and will head towards Dodge City.

One thing to watch for later: Recent NAM runs consistently show a frontal wave developing between 21-00z in south central Kansas. If this does come to pass, any storms tracking the warm front behind the wave could quickly get undercut as the front surges back south. Meanwhile, conditions just ahead of the low center would be ultra-primed for high-end supercells.”

Team Duck (John and Rose) Forecast:

“A complex scenario is likely to evolve today in the central plains (13Z surface analysis attached). A diffuse surface low lays over the western plains, straddling NM/CO/west TX PH, a stationary front extends east from the low along the OK/KS border into eastern KS, and a sharp dryline extending through western OK and into western TX. This low is forecast to strengthen and track east-northeast toward the eastern PHs, with a triple point establishing itself in the corridor from DDC toward Greensburg and a stationary frontal boundary that drapes eastward toward KS City with an inflection west of ICT. Rich boundary layer moisture has advected north from the Gulf since last evening on the LLJ and in the mass response, for example see DFW sounding this morning: http://climate.cod.edu/data/raob/KFWD/skewt/KFWD.skewt.20170518.12.gif with a 1500m deep airmass in the 70s. INVOC the triple point, the moisture is forecast to reach the mid to high 60s, if not low 70s as a response to strong low level advection with the lee cyclogenesis.

I’m going to play the devil’s advocate for today’s forecast. While SPC is going with a high at this stage (overnight issuance at 06Z) there are a few flies in the ointment (as always on a high risk).

1. Storm Mode – most of the CAMs are suggesting a strong chance of upscale growth and excessive storm coverage throughout the warm sector. In that scenario it will be needle in a haystack territory.
2. Timing of initiation – some of the CAMs want to blow up a convective mess early, which leads to a deprecated environment that potentially recovers – or doesn’t depending on the solution. Trends are towards a double round of initiation – a first wave and then a second wave that fires on the dryline/triple point.
3. No good discrete storms in the favorable environmental space. This scenario seems somewhat unlikely, but the potential for a mixed mode like this could see a big squall line make things messy.

Most CAMs place initiation in the 20-21UTC timeframe. Experimental HRRR throws things too far east, but is a slightly kinder scenario than the operational which blows up one giant of an MCS/embedded cluster, particularly INVOC the TP. GFS is displaced a little too far east, NAM is also questionable on location. So where to be – well my feel is that we want to be in the DDC/Greensburg corridor for the TP play – the backed winds, the maximized shear profile, excellent instability and good moisture availability. How we play may depend on how east storms turn – it may be challenging to keep up with the storm motion given the nose of the jet is squarely pointed at NW OK and SW KS. I would also keep an eye on the trends and whether a second round might be feasible (around ~ 00Z initiation). It might also be worth keeping an eye on the wraparound potential – impressive shear and quite a few interesting discrete helicity tracks with run-to-run consistency – which may also be worth paying attention too, though the storm motion will be fast.

I’ll update as things evolve, and deal with Day 2 subsequently – my initial feelings are for SW OK on the dryline though boundaries from today may play a large role. We are remaining in Greensburg for the moment until things become clearer about the westward extent.”

With a 30% probabilitistic forecast for tornadoes, the Storm Prediction Center had issued a categorical High Risk. The morning of a high risk brings excitement, nervous butterflies, and loathing at what could turn out to be a major catastrophe for those in the path. Our three vehicle convoy assembled at a lakeside park in the town of Greensburg, KS. Our research goal is to gather multi-perspective video of tornadoes to learn how they operate in the lowest levels, below where radars can see. We always hope that our chases don't involve a disaster, but these are the kinds of events that could potentially give us high profile, violent tornadoes to study.

Greensburg is hallowed ground. The town was destroyed in 2007 by an EF5 and several residents were killed. The land is still scarred and large parts of the town were not rebuilt. The recovery of Greensburg and its investment in green energy have been inspirational, however. We lingered on the outskirts, and were careful not to flaunt ourselves as chasers like those who festoon their vehicles with lights and stickers. The last thing the residents of this town want to see is a parade of storm chasers hoping for a big, violent tornado. Greensburg was our target, but we of course hope that the tornado tracks over the vast empty landscape surrounding the town and doesn't make a tragic bullseye like it did in 2007.

By early afternoon the air was warm and rich with moisture. Cumulus bubbled above the lake and moved in the mounting wind shear. Our position by the water, the feel of the high dewpoints, and the tornado parameters were reminding us strongly of our El Reno chase, another major disaster from 2013. I think Anton and John remained excited for the day's prospects, but the high risk and reminders of infamous past events were giving Brindley and I the heebie jeebies.

I finally had a fully operational chase setup in the Forester and this was our first trip to the Plains with it. I constructed a monitor stand out of PVC for the 22" touchscreen, was using a suction mount for the 4k camcorder, and had a dash mount for the cell phone.

Internal vehicle shot from our chase on the 16th to show the chase setup from the other side:

The monitor stand is constructed from heat bent PVC. It curves flush against the center console and so consumes none of Brindley's passenger space, but is sturdy enough to hold the bulky monitor, anchored to the floor by the passenger seat bolt.

There wasn't enough capping on the warm front and the whole atmosphere started to overturn all at once. Cells were conflcting with each other and training on the front near Great Bend. We were well positioned at the start of the chase, but storms exploded and organized so quickly that we were playing catch-up and missing the show right from the start. A dominant supercell near Great Bend produced a small trunk shaped tornado before we could even get to it. A hazy, low rear flank downdraft clear slot came into view as we approached from the south.

As we arrived on the scene in Great Bend, storms were congealing, falling apart, and moving swiftly to the east in the highly sheared environment. We couldn't keep up and we had no view of any noteworthy supercell structure anyway. A storm on the heels of what had been the dominant lead storm was showing an impressive hook, velocity couplet, and was tornado warned just a few miles to the west. We could move in for an easy intercept. It was squarely behind the lead complex's gust front and moving over hail and rain cooled air. While it looked like an amazing supercell on the radar, we were worried that it would be undercut by the lead storms and unable to produce. Still, storm mode to the east looked dismal and I didn't think we even had a shot at catching up with the fast moving storms as we were slowed down in the middle of Great Bend. I opted to turn us west. The training cells were dumping rain on Great Bend and started to cause some minor flooding. Luckily it was localized and we were clear of town within a few minutes.

Highway 96 took us northwest out of town and straight into the storm's inflow notch, north of the hook. The tornado warned supercell came into view quickly, and what a beast it was. A massive, ground scraping gust front seemed to span the entire southwest sky. Inflow fingers stretched over our heads and fed directly into it from different directions. Inflow winds screamed toward the storm, but they were icy cold, chilled from the hail and rain of the storms to the east just as we had feared. With what looked like a giant shelf cloud sucking cold inflow, I was convinced that the storm was elevated or at least didn't have the low level thermodynamics for a tornado.

Anton and Tracie caught up with us, but John and Rose got separated from the caravan in Great Bend and bailed off the storms. Anton and I didn't like our prospects at first, and I was convinced we were chasing scuddy shelf cloud. But Anton noted that the inflow fingers were all converging into a central part of the storm, and motion underneath was rapid.

Was that a wedge underneath? We couldn't tell if it was a tornado or just a low rise in the terrain obstructing the view underneath the ground scraping base. Scud and lowerings were intensely churning, however, and we watched it closely. In hindsight, this was most likely part of a large tornado cyclone that hadn't formed a mature tornado yet.

Small vortices to start to kick up under the base. I couldn't believe it. The storm was trying to make a tornado with a laminar base and cold inflow, which screamed elevated to me.

A parade of vortices began, which I suspect were subvortices beneath the parent tornado cyclone. The rear flank gust front was filling most of the southern and western sky now and moving in our position. With the scale of the storm, the lack of a focal point for the vortex parade, and our diagonal roads, we had a tense few moments trying to decide what our best escape route was if we needed to flee.

The tornado cyclone was moving solidly to our south, however, so we held our ground and watched as vortices continued to spin-up at random beneath the base.

A rope funnel crossed the road a couple miles to our south.

The tiny vortex was the closest thing to a conventional looking tornado that we had seen all day. Despite the numerous ground contacting funnels, I'm counting this as one multi-vortex tornado as I believe they probably originated from the same parent circulation, and each spin-up lasted mere seconds, not long enough to justify counting as separate tornadoes. Had this storm had some warm, high CAPE inflow, it probably would have produced large, violent wedge tornado. Instead it probably couldn't get out of the "pre-tornado vortex" stage, accumulating ample vorticity but not enough low level instability.

The storm was encroaching on our position so we ran southeast and then east to stay north of the Bear's Cage region, flood portions of Great Bend, and in front of the storm. The tornadic activity didn't last long and the storm soon started to blast outflow, kicking up a big shelf cloud. It was finally starting to behave more like how I was initially expecting. We stayed ahead of the storm for several miles before calling the chase as the warm front looked like a junky mess with no chaseable targets left. Then we trekked down to Wichita to grab dinner and a room for the night.

Team Duck’s Summary:

“Beginning the day in Greensburg, a potent setup appeared likely through western KS, western OK and northern TX. Rich low level moisture at around 68F was projected to shift northwestward around a surface low in the eastern TX panhandle, OK panhandle, and southwest KS region. By 19Z, storms had erupted along the dryline in TX and southwest OK associated with a fast-moving shortwave ejection into north-central OK. One of these storms quickly became tornadic, but we remained in the favourable environment associated with the triple point extending westward from Greensburg KS, where the low level wind field veered the greatest amount, and the potential for significant tornadoes appeared to be maximised.

After waiting by the Greensburg Lake until 20:45Z, based on storms moving north from OK creating anvil shadowing, we shifted position north toward Kinsley in the vicinity of the warm front, where cells were beginning to initiate north of Pratt. From Kinsley, we tracked northeastward along highway 56 toward Pawnee Rock, making an east turn at Larned to pursue a cell lifting north from St John to Great Bend, which quickly became severe warned, and tornado warned shortly thereafter. This storm may have produced a brief tornado.

As the environment began to get more cluttered, our eyes turned west toward a tornado warned storm approaching from the southwest. Positioning toward Albert, having driven through substantial standing water in Great Bend, we positioned to observe a broad mesocyclone that produced tornadic circulations viewed by teams Turtle and Woodchuck.

As the cells interacted and grew upscale, the tornado threat diminished. While a couple of warnings persisted on the warm front, and with the newly developing cells on the recovering air mass further west toward Dodge City being out of range, at that point the day was called and teams positioned for the following day. Overall for a high risk forecast, this day was somewhat disappointing, and team Duck could be found that evening drowning their sorrows at a local mexican, where the salsa wasn’t hot enough, but thankfully the food was.”