2013-05-18: Rozel, KS tornadoes

Rozel, KS tornado

Rozel, KS tornado, about 4 miles away at 7:34 p.m. CDT. The view is to the NW.

This day proved to be one of my favorite chases in the last five years. I saw two long-lived, photogenic, slow-moving tornadoes. The only thing that could have made it even more perfect would have been the absence of property damage. (Even when it is “just a house” destroyed, it still belonged to someone!) At least there were no injuries.

Given that it was a moderate-risk Saturday in what had theretofore been a rather lackluster, non-stormy May, we expected Kingfisher-esque crowds of storm chasers in western Kansas. In a bid to reduce the number of cars on the roads, Dan D. and I took two passengers along: Dan S. and Steven. W. of the UK Met Office, who were in Norman for the HWT Spring Experiment. Neither of them had seen a tornado before.

We found the crowds in Greensburg, KS – site of an infamous EF-5 tornado six years earlier. With that heavy history weighing on us, we spent a couple of hours hobnobbing with other chasers, munching convenience store food, and watching elevated showers percolate behind the dryline. In the meantime, a storm up near Ness City began to entice us with a hefty, 60 dBZ hail core and hook echo – but we judged it was too far away, and moving away too quickly, to be a viable target for us. One tower finally solidified northwest of Greensburg around 5 p.m., and we headed up U.S. Hwy. 183 to investigate. Its base was elevated, but persistent. We waffled on whether to stick with this target, or head back south to a less-organized cluster of thunderstorms in Lipscomb Co., TX. We eventually chose the bird in hand, and followed our target storm into Kinsley, KS.

As we drove through Kinsley, our radio crackled to life with reports of a high-based funnel beneath our storm’s still-elevated base. We spotted at least three of them between the buildings and trees. We continued north up U.S. Hwy. 183, and stopped once we noticed that our storm – now a supercell – was merging with a second, more modest cell approaching its right flank. (Part of my current research investigates whether this type of merger is beneficial to tornadogenesis. There are some anecdotes suggesting this might be the case.) We parked about four miles south of the intersection of U.S. Hwy. 183 and KS-156, where we watched the bases of the two storms merge and the cloud base drop.

Soon enough, the wall cloud extruded a few rotating scud fingers. We gingerly stepped out of our car (a few CGs were striking too close for comfort) and set up our tripods. Sure enough, around 7:15 p.m., a funnel cloud drilled lazily downward to our west. Over the course of the next several minutes, it morphed into a majestic stovepipe, and finally a symmetric cone with a flared dust cloud around its base. The funnel appeared to occlude at least two times, and disappeared entirely before returning for an encore performance. Our two guests from the UK seemed suitably impressed. This tornado is now known as Rozel, KS, tornado, in reference to the nearest town.

Sanford, KS tornado rope-out

Protracted rope-out phase of the Sanford, KS tornado. At this point, the condensation funnel was completely detached from the cloud base overhead.

The storm was now north of our latitude, so we packed our gear back up and headed east on KS-156. We hadn’t gotten more than a mile or two before Dan D. hollered for me to stop the car. In a field less than a mile to our north, a new lowering and dust whirl were visible. I backed into a small pull-off and we all set up our tripods again, watching as the Sanford, KS tornado took shape. From our vantage point, it moved from right to left, then back from left to right, then reversed its course yet again. (Watch my time lapse footage near the end of this video.) These motions may have been in response to rain-filled downdrafts that we observed in close proximity to the funnel.

As with the Rozel tornado, the Sanford tornado appeared to dissipate completely before returning for an encore (zombie-nado?). This is why I always try to leave the camera running for an extra minute or two when the show is apparently over! We called off the chase in Larned, KS, before heading to Wichita for the night.

The situation gets serious

I am still getting my bearings back after three straight days of tornadoes. Yesterday, I watched the Moore tornado form from the controls of the KOUN radar on the north side of Norman.

It was my first time to see a tornado while not actively chasing. As I watched it track past me to the northwest and disappear into the murk, I crossed my fingers that it would spare Moore. It didn’t. It crossed I-35 between 4th and 19th street, scattering cars, houses, and people like a mammoth lawn mower. The Warren Theater, where I watched a sneak preview of the new Star Trek movie last week, was damaged and pressed into use as a triage area.

I was ready to write two relatively light-hearted posts about my chases last weekend. I just don’t feel that lighthearted anymore. A co-worker of mine lost her home, but fortunately is not injured. My husband and I are going to go through our garage tonight and gather items to donate to people a few miles away who literally lost everything they own. Honestly, how many times can a nightmare repeat itself?

Quality, not quantity

Yesterday is already wrapping up to be one of my best chases in years. I witnessed two long-lived tornadoes – one at 6:30 p.m. CDT near Rozel, Kansas, and the second at about 8:00 p.m. just north of Sanford, Kansas (which we watched from less than a mile away). I shot more than 40 minutes of video and boatloads of stills, and it is going to be some time before I can sort through and upload the highlights. Unfortunately we have learned that one of the tornadoes destroyed a home in Rozel, and our hearts go out to the victims as they begin to put their lives back together.

Today is also shaping up to be a big chase / tornado outbreak day, and we have some crucial decisions to make. So for now I will just leave you with a teaser. Stay safe today in OK, KS, and MO!

Sanford, Kansas tornado at about 8:06 p.m. on 18 May 2013.

Sanford, Kansas tornado at about 8:06 p.m. on 18 May 2013.

Fun with a Texas dust devil

The Texas panhandle was crawling with dust devils near yesterday afternoon’s dryline. We were en route back from Boulder, when one of them passed over U. S. Hwy. 87 in front of our car. My husband grabbed my Sony Bloggie 3D and shot this as the dust devil passed over him. He complained for about an hour afterward that he itched from the tumbleweeds scratching against his bare legs!

Minnesota Skywarn Workshop recap

It’s been a busy month! Immediately after the VORTEX2 science workshop, I traveled north to deliver a keynote talk at the 7th Annual Minnesota Skywarn Workshop. What a difference 15 degrees of latitude makes! Minnesota greeted me with a refrigerator chill. I reverted from a summer dress I wore in Texas back to a winter coat and gloves. No great surprise there – when I was growing up in St. Paul, I remember slushing it to the bus stop as late as the first week of May in some years.

The workshop’s organizer, John Wetter (Skywarn coordinator at NWS Chanhassen) had contacted me about a month earlier to ask if I would be interested in speaking. I jumped at the chance to reconnect with the weather community in Minnesota. And yes, I’ll admit to wanting to visit home for myriad personal reasons. They got a keynote speaker, and I got a trip back home. It was a win-win.

John Wetter (in red) introduces me at the afternoon session of the 2013 Minnesota Skywarn Workshop.

John Wetter (in red) introduces me at the afternoon session of the 2013 Minnesota Skywarn Workshop. Thanks, Dad, for the picture!

The workshop featured a nicely balanced cross-section of stakeholders: professional meteorologists (mostly op-mets from the NWS-Chanhassen and Duluth offices), EMs, members of the media, and educators. The audience members ranged widely in age, and all were keenly interested in all the talks. For my part, I spoke about the use of mobile radar in scientific storm chasing, and how it was about more than just pretty-looking data. I covered topics like dual-Doppler, EnKF, and GBVTD analyses, and of course, fresh results straight outta da VORTEX science workshop from which I’d just come. I worked in some networking between sessions. Near the end of the day, the speakers participated in a panel about social media and other factors influencing the future of Skywarn. I was impressed with the workshop organization; everything went smoothly as silk.

My talk was sourced mostly from my own work, but also from a large number of contributors. Here I credit several people who sent me slides, including Howie Bluestein, Jeff Snyder, Jana Houser, Mike French, and Vivek Mahale. I also knew I needed to include some mobile radar data collected in Minnesota in order make the talk locally relevant. (Our observations tend to be Great Plains-centric, just because of fuel costs.) Mike Biggerstaff, Gordon Carrie, and Kyle Pennington generously shared their results from SMART-R observations of the 17 June 2010 Albert Lea, MN tornado (collected during the VORTEX2 “epilogue” period). Thanks, guys!

The organizers were even kind enough to waive the registration fees for a few of my family members, so they got to enjoy the day’s program and learn useful skills like dual-pol radar interpretation. I’m particularly glad my uncle (former EM for Winona County) and aunt made the two-hour drive up to the University of St. Thomas, even though one of their horses was about to give birth. (Incidentally, the foal – a filly – was born the very next morning.)

I spent the balance of the weekend visiting friends and family. I returned to Norman both professionally and personally satisfied. Thanks, John Wetter, for giving me the opportunity to speak at this well-run venue and make a long-overdue visit home!

VORTEX2 science workshop recap

It’s been nearly three years since the field phase of VORTEX2 ended. Two weeks ago, a group of about 30 PIs and scientists reunited at a retreat near Austin, Texas. I was asked to send a few tweets from the workshop since the V2 media liason wasn’t in attendance.

VORTEX2 science workshop group photo

VORTEX2 science workshop group photo

At the end of the field phase, the PIs divided up case studies and initiated collaborations. Over the three-and-a-half days of the workshop, participants updated the group on their most recent findings, including low-reflectivity ribbons (a feature whose significance is still not completely clear), an apparent case of bottom-up tornadogenesis, an uber-composite supercell environment generated from over 700 rawinsonde launches, and UAV transects across multiple gust fronts. There were also discussions about lessons learned (particularly from the UAV group), new tools (EnKF analyses have proven to be a popular tool for filling in the spatiotemporal gaps between observations), and directions for the future.

In the past three years, life has changed for many of the participants. Some have changed jobs or institutions, graduated (waves), or had families. In spite of all this mobility, electronic collaborations and conferences have enabled quick dissemination of results. (It took 10 years for some results from the original VORTEX to see print.) Josh Wurman aggregated a list of all the peer-reviewed VORTEX2-related manuscripts published so far: the paper count currently stands at 14, with 9 more either accepted or in press. It was decided that the group will shift focus in the next few years towards synthesis studies rather than individual case studies.

It wasn’t all work, of course. There was time for some fun, including a zip line ride across Lake Ted!

2013-04-17: Wall clouds in SW OK

KFDR reflectivity image of the Faxton storm

Cutting south across the forward flank of the first Faxton, OK storm on April 17.

It was my first day back at work after a long week of travel that spanned nearly 15 degrees of longitude. (More on that later.) I went into work extra early, and managed to scramble a chase partner (Gerry C.). We departed the NWC just after 2 p.m., and headed southwest on I-44. We initially targeted a storm west of Anadarko, OK, only to abandon it quickly when its high cloud base made frontal undercut evident.

Next, we cut across the forward flank of a tornado-warned supercell passing over KFDR, intercepting it near Cache, OK. Sitting on top of a hill on Cache Road just north of Faxton, OK, we observed a wall cloud to our distant southwest that extended a few enticing purple scud fingers. However, it quickly filled from behind with emerald green and gusted out toward us.

Faxton, OK Wall Cloud

Faxton, OK wall cloud about 5 p.m. CDT, as seen from Cache, OK

We escaped east toward Lawton with numerous other chasers, but were overtaken by the advancing core. A few nickel-sized hailstones thumped against my roof. I dropped a few miles south on SW 82nd Street and allowed the Faxton storm’s hook to pass by us to the north.

By this point, it was evident that a second supercell – following an almost identical track over KFDR and Manitou, OK – was now the tail end Charlie and the preferred target. Proceeding west along Baseline Rd., we stopped near the intersection with Indiahoma Rd. where we had a good view toward the west and a new wall cloud. Unfortunately, that wall cloud met the same fate as the last one – after rotating lazily, it grew increasingly Z-shaped as an advancing gust front pushed it out from behind.

It was growing darker, and we both needed to return home for logistical reasons. As we merged back onto I-44 at Lawton, we heard a spotter report of a tornado near Ft. Sill, a few miles to our northwest. Our view was blocked by trees, but we could see a dark lowering beneath the cloud base in that direction. We pulled off I-44 for a few minutes to observe, but never saw a tornado or the reported power flashes. We missed the Grandfield tornado, which happened even farther to our southwest, after dark.

By then, the southwest-to-northeast oriented line of supercells was now situated over I-44, signifying a slow and messy return drive. Lou W., who had been nowcasting for us via text message from back in Norman, suggested that we drive straight east through Duncan to I-35, and return to Norman that way. It added about 30 miles to our drive length, but was precipitation-free for all but the last 10 miles. We took the Lindsey Street exit just as our old target storms congealed into a mini-bow. The next morning, my home rain gauge had 2.1 inches of refreshing rain in it.

For your amusement, here’s a video clip from Chris Novy showing spotter network activity during the 17 April event. Despite the number of glowing green ants, we didn’t run into any horde-related issues. We found decent parking spaces and observed safe driving habits all around.

A storm observer’s pledge

Inspired some behavior I’ve witnessed on YouTube recently…

As a research meteorologist, storm chaser, and an admirer of the atmosphere, I hereby pledge that:

  • I will conduct myself professionally, regardless of whether or not I am observing a storm as a duty of my employment.
  • I will obey all federal, state, and local laws.
  • I will never misrepresent who I am or in what capacity I am observing a storm. I will never impersonate a law enforcement officer or emergency responder.
  • I will conduct myself safely and ethically, even if doing so costs me a “money shot.”
  • I will report promptly any hazardous conditions that I observe to the NWS, and share my insights with local authorities.
  • I will never willfully imperil myself or others, thereby diverting emergency resources from the local population.
  • I will not operate a handheld camera while driving. I will ask my chase partner(s) to take images and video for me.
  • I will never exploit tornado victims for personal gain.
  • I will not cheer on a tornado, since I can never know what’s beneath it.
  • I will admit promptly to my mistakes, and offer explanation and redress.

Minnesota Skywarn Workshop

Just a heads up that I will be giving a keynote talk at the 2013 Minnesota Skywarn Workshop on Saturday, 13 April 2013. As many of you know, I grew up in the Twin Cities, so this venue is a perfect fit for me. I’m looking forward to the chance to visit my old stomping grounds and reconnect with the spotter community up north. Minnesota weather weenies (and yes, I still count myself among them) are a very special breed!
2013 Minnesota Skywarn Workshop

New pub

This month’s issue of Monthly Weather Review contains my newest paper, EnKF assimilation of high-resolution, mobile Doppler radar data of the 4 May 2007 Greensburg, Kansas supercell into a numerical cloud model, describing the second half of my dissertation research. (Yes, I know I graduated over a year ago… Publication takes a long time, as well it should!) The take-home message of the paper is that low-level (< 1 km AGL) wind observations make more realistic analyses of supercells (and other rapily-changing atmospheric phenomena). Supercells have a lot going on under the hood – updraft and downdraft pulses, mesocyclone cycling, cold pool generation, etc. – not all of which are apparent to the naked eye or even to an advanced, 4D observing system like a radar. Computers can help fill in some of the gaps via process called data assimilation (DA).

For those not familiar with DA, it means combining atmospheric observations (such as those from a radar) with a computer-generated weather forecast in order to produce a mathematically optimal, 3D analysis of the atmospheric state. You then use the analysis to launch a new forecast. Rinse and repeat every few minutes. The end result is a series of 3D snapshots of the storm, which you can use to diagnose the storm’s inner processes. (There is a gargantuan body of theory required to combine these two very different types of input and assess the quality of the analyses. I shan’t bore you with the two semesters’ worth of details that I slogged through in grad school.)

For this study, I used an advanced DA technique called the ensemble Kalman filter (EnKF) to assimilate NEXRAD (from Dodge City, Kansas) and UMass X-Pol data collected in the Greensburg storm. In one set of experiments, I withheld the UMass X-Pol data (which were collected more frequently and closer to the surface). The mesocyclone of the simulated Greensburg storm was much stronger and more persistent in the experiments where I used the UMass X-Pol data, and the updrafts and downdrafts stronger and more compact. While we lacked independent data to use for verification, making our assessment necessarily qualitative in some regards, our results are consistent with previous DA studies using artificial, “perfect” radar observations.

Simulated Greensburg storm (reflectivity)

Here’s the simulated reflectivity in the Greensburg storm, after assimilating (left) WSR-88D data only and (right) also UMass X-Pol data. Both storms are in the same place and look similar overall…

Simulated Greensburg storm (vertical velocity, vorticity)

BUT… the velocity fields are very different! Updrafts (red) and downdrafts (blue) are more intense. Also, the vorticity bullseye corresponding to the Greensburg tornado (black contours) is much stronger.

I described in a previous post our serendipitous UMass X-Pol data collection in the Greensburg, Kansas storm of 2007, and how that evolved into a detailed case study published last year. My husband lead-authored a companion study earlier last year where he assessed whether modifications to the initial model environment changed the forecasts. (Answer: Yes. Quite a bit, in fact.) This pub completes the trifecta. As we were about to submit this paper for peer review, we made a last-minute decision to switch the DA software to a system that was more extensively tested for severe storms. Even though that added a month to the prep time, I am glad that we did, because the resulting analyses, generated from the same observations, looked markedly better.

I wrote this paper during my CAPS postdoc with the able assistance of my co-authors, representing a fruitful collaboration between SoM, NSSL, and CAPS. I manually edited and dealiased all the radar data (a task that took nearly two months). I had the benefit of two astute reviewers (including my brother-in-EnKF, Dr. James Marquis) who asked some mighty tough questions. And I got to share this MWR issue with some other super scientists – Tom Galarneau, Jeff Beck, and Chris Weiss.