Friday, May 28, 2010

Matt Hughes

This has been a sad couple weeks with Wichita chaser Matt Hughes (of Discovery Channel's Storm Chasers show) hospitalized in serious condition, and then passing away this past Wednesday. I am so very sorry for his family's loss.

I haven't known Matt for very long, but it is clear he was a bright and enthusiastic person, with much passion, and also very sensitive.

With the deadly Yazoo City MS and Oklahoma City OK tornadoes this year, and now Matt's death, I hope these events will serve as reminders to weather enthusiasts that there are more important things in life besides storm chasing, and to keep all that in its proper perspective.

Matt, we will remember you fondly...

- Jon Davies 5-28-10

Friday, May 21, 2010

Brief "chaser convergence" thoughts, and Missouri cold core tornado setting 5/20/10

Wednesday's massive chaser convergence and careless driving in central Oklahoma has been a huge topic of conversation the past couple days. Shawna and I actually decided not to chase that day because of the expected chaser hordes and narrow severe focus in central Oklahoma, and we both had work to do. Sometimes one asks, "If there's already hundreds of people out there shooting the same storm, what's to learn and what's the point of being out there adding to the dangerous traffic jams?" Wednesday was just such a day. Things don't look to improve in similar future situations, unless someone gets killed in traffic and it is well documented. Shawna and I are getting increasingly picky about going out on "big" days with a small focus drawing hundreds of chasers and weather yahoos to the same spot.

Anyway, stepping away from the situation in Oklahoma, Wednesday 5/19 brought some "cold core" action to the Garden City/Dodge City area of southwest Kansas in the form of "landspouts" along a surface boundary close to the 500 mb low, photographed nicely by Mike Umscheid. And Thursday 5/20 brought a few "cold core" supercell tornado reports to the Sedalia area in Missouri east-southeast of Kansas City (see photo above). I had family visiting in town, so no storm chasing for me or Shawna. But with my interest in such settings, the Thursday setup is worth documenting briefly. Thankfully, as with most "cold core" setups, none of the tornadoes were strong.

The 2nd graphic above shows visible satellite with overlaid surface and 500 mb features at 2145 UTC. Notice the boundary intersection in west-central MO, similar to the "cold core" tornado composite shown in this paper. This can be a favored area of severe focus (enhanced low-level shear and forcing) for tornado development when a midlevel low (strong cold air aloft) is nearby to the west (northeast KS on 5/20) and there is some instability. In this case, the N-S boundary wasn't a dryline, but a subtle wind shift intersecting the warm front southwest of Sedalia at late afternoon, notable on satellite along with some clearing for sun's heating. The 3rd graphic shows selected images from the SPC mesoanalysis at 2200 UTC , including the midlevel low, total CAPE (near 1000 J/kg over west-central MO, but certainly not as impressive as down in Texas), low-level CAPE (a significant maximum near the boundary intersection), and SRH (enhanced northeast of the warm front, but probably under-represented closer to the front in west-central MO). The presence of the 500 mb low in northeast KS and the low-level CAPE maximum over west-central MO near the boundary intersection were probably the biggest "heads-up" flags seen here for tornado potential in what otherwise looked like a fairly benign environment.

The 4th graphic above is a radar image at about 2340 UTC when the tornado in the photo above (likely EF0) was occuring near Sedalia (see arrow for cell location). The RUC analysis at 2300 UTC (last graphic above), as with many "cold core" type settings, showed most of the CAPE below 500 mb, suggesting sizable low-level stretching. The model-derived estimated hodograph (same graphic) suggested good clockwise curvature to the wind profile and more low-level shear than shown on the SPC mesoanalysis during the afternoon. So, while not an easily forecast event, the presence of these ingredients suggested taking rotational signatures on the nearby Pleasant Hill MO radar and spotter reports very seriously. Indeed, the Kansas City area NWS office did a good job jumping on the situation with tornado warnings and statements as the situation developed and evolved prior to the Sedalia tornado, which is what situational awareness is all about.

- Jon Davies 5/21/10

Saturday, May 15, 2010

Monster Medford OK meso & tornadoes 5/10/10

My wife Shawna, her son Zach, and I intercepted the large supercell near Medford OK last Monday (5/10/10). As a rule, I don't chase storms going 50+ mph, but we decided to try it, given the high-end potential tornado environment (see significant tornado probability mesoanalysis graphic for 20z, 2nd image above, an experimental product that Bill Togstad in Minneapolis and I have been working on). We were prepared for very fast storm motions, probably giving us only a few minutes of intercept time.

There were many chasers on the Wakita-Medford storm, but we managed to avoid most of the crowds (and all the road "drama" south of Wakita) by pulling off on a county road 5 miles north of Medford and letting the dangerous storm come toward us. As it emerged from the haze and broken low clouds near Medford around 3:50 pm, the mesocyclone at first appeared to be rain-wrapped, but then we could begin to see features behind the rain curtains, including a narrow tornado on the north side of the meso (see 3rd image above, please excuse the poor video quality). We were using WxWorx due to some internet problems, and Threat Net was indicating that the meso would pass just to our northwest. Not so! It quickly became apparent that the storm was moving more rightward/eastward, and that we needed to move south FAST, out of the path.

It was unnerving to see a meso that large coming toward us at nearly 60 mph (a mile a minute!), and the pressure drop with the fast movement was causing our ears to "pop", the first time I remember experiencing this with an approaching mesocyclone. As we blasted south, the first tornado dissipated, and a larger one formed near the center of the meso, with rain and dust curtains moving around it. In fact, thoughout much of the meso, what appeared to be wispy "spin ups" and brief condensation columns were also occurring, causing us to wonder if much of the mesocyclone might actually be a very wide lower-end "tornado" a mile or more across, with more intense vortices moving around inside it (see 4th image above). There's certainly no clear-cut answer to that. Regardless, we needed to get out of the way.

As the larger cone tornado within the meso sped toward us (see 1st image above), we cleared the path of the meso and RFD winds to the south, and pulled over just north of Medford. Looking back to our north, the tornado(es) were no longer visible, as rain and hazy sunlight obscured our view (chasers farther east reported seeing only a rain-wrapped meso at this point). Looking to our west, we noticed an anti-cyclonic wall cloud and circulation on the trailing gust front (a feature not that uncommon), whch produced a very brief spin up beneath a small condensation funnel aloft (not shown). With the incredibly fast storm motion, our chase was over in only minutes, and Shawna's son Zach had videotaped his first tornado(es).

The last graphic above is a schematic and approximated path of this large fast-moving mesocyclone (several miles across), one of the largest and fastest I've ever seen. Despite the damage path from near Wakita OK to east of Arkansas City KS, it was great to hear that there were no deaths or serious injuries from this dangerous supercell.

For those on Facebook, additional video captures are under Shawna Davies' photo folder titled "5-10-10 Medford OK meso /tornadoes".

- Jon Davies 5/15/10