Quincy

Chased the long lived supercell in western Oklahoma and it’s heading in the general direction of Oklahoma City. Hopefully it weakens.

PDS severe thunderstorm watch for northwestern Oklahoma and much of Kansas. 50/20 tornado probabilities too. Recent WoFS runs show expected storm modes nicely: clustered, bowing segments in Kansas with isolated supercells in northwestern Oklahoma. Low level moisture is over performing some progs. Upper 60s dew points are common across western Oklahoma with lower 70s not far downstream with a 25-30 knot low level jet already in place. 15-25 knot, backed near-surface winds will keep moisture streaming NW. Live updating dew point map: 18z NAM is very bullish, showing several supercells along the dryline from western Oklahoma, even down to western north Texas by early evening. I’m not sure I buy that, but regardless, any sustained convection in western Oklahoma will have the potential to produce significant severe. Edit: Now the 19z HRRR initiates a tail end supercell just south of I-40 in western Oklahoma.

Having reviewed 00z guidance, it certainly looks interesting near western Oklahoma early Sunday evening. Models show troughing across the High Plains with subtle lee cyclogenesis over southwestern Kansas. A belt of enhanced upper level flow should reside from New Mexico across the OK/TX panhandles and into Kansas as the mid level wave ejects. Convective initiation seems likely by mid afternoon near an effective triple point over SW Kansas and with warm advection farther north in central/northern Kansas near a pseudo warmth front. Capping and initially larger T/Td dew point spreads along the dryline over the eastern Texas panhandle will delay convective initiation until late afternoon. With that said, most 00z CAMs show at least one or two isolated storms going up ahead of the dryline by 22-00z. If sustained convection is realized, any storm would move eastward, into western Oklahoma, where increasingly richer moisture will reside. This along with an increasing low level jet would conditionally favor intense supercell development and an associated tornado threat. Given that messy storm modes are more likely across Kansas, the southern target certainly has my attention. Especially given a southern stream perturbation pointing right at the dryline, just south of the surface low.

The expected pattern realignment is underway. The derecho across Texas yesterday was partially driven by a cold front surging toward the Gulf of Mexico, effectively scouring seasonably rich moisture out of the Plains. Things will be changing in the coming days. Saturday: Split upper level flow continues tomorrow with the subtropical jet positioned along the Gulf Coast and the northern branch ejecting out of the Northern Rockies. The result may be a bit of a break in the severe action, largely due to a lack of stronger flow/deep layer shear across the Plains. However, a few marginally severe storms and perhaps a transient supercell or two can’t be ruled out across Kansas, as a front drops through the area. Sunday: It looks like the first potentially active day in what should be a fairly busy stretch for severe weather across the region. The setup appears just a bit disjointed, as a split flow regime hangs on. The southern branch is progged to be ejecting toward the OK/TX panhandles and KS, while the northern branch remains displaced to the north. Nonetheless, at least isolated to scattered severe thunderstorms, including a few supercells, seem probable across the central/southern Plains. Forcing will be modest and only weak Lee cyclogenesis is expected over the western Kansas vicinity. Details are still TBD, but it looks like a modest-caliber event for late May standards, but still worthy of storm chasing. Monday: Medium range models show some phasing of the upper level jet, as a trough digs from California toward the Desert Southwest. Due to westward placement and “late” timing, it does not look like a major event, but at least some severe potential should exist, once again around the central/southern Plains vicinity. Tuesday: It’s several days out, but there’s good model agreement that the next notable trough ejection will take place. Models show a robust, broad upper level jet across the central states. Confidence appears highest for severe potential around the lower Missouri Valley vicinity, somewhere around Iowa/eastern Kansas/Missouri. Details will need to be ironed out, but the synoptic pattern favors a heightened severe threat. This may extend as far east as portions of the Mississippi Valley, but we’ll see. Midweek and beyond look generally active, but moisture may be scoured out of most of the plains on Wednesday, behind Tuesday’s system. Even if that is true, moisture recovery seems likely by late week, along with ensemble guidance favoring enhanced upper level flow across the Plains. The result should be continued severe threats most days, right through Memorial Day weekend.

As we move toward the peak of severe weather season, the medium range guidance has come into fair agreement with the potential for an uptick in severe thunderstorm activity across the Central United States. The first half of next week has potential, but threats could begin by this weekend (May 18-19). Since we’re near the climatological peak of the severe weather season. I decided to group the time together, as ensemble signals suggest an active stretch may linger through Memorial Day weekend and beyond. The synoptic pattern appears to be going through a shift this week. As of now (May 14), upper level ridging is developing across the Pacific Northwest. A series of low amplitude shortwaves will dig toward the Southeast, most notably around the May 16-17 period, before pattern realignment takes place. SPC has outlined a Day 4 risk area across the Lower Mississippi Valley vicinity as this takes place and MRGL/SLGT risk areas precede that over the next 1-3 days. This weekend, May 18-19, ridging is expected to build across the south-central states, as troughing digs across southwestern Canada. There may be some severe potential around this timeframe across the Central Plains vicinity. Early next week is when ensemble and analog guidance suggest a broader scale, severe-favorable setup develops across the western/central US. Details are TBD, but the general pattern may support troughing across the West, ridging shifting toward the Lower Mississippi Valley and enhanced upper level flow overspreading the southern/central Plains. It’s too soon to speculate about any major trough ejection or individual day that might feature the greatest threat. Operational runs of the Euro and GFS vary with trough amplification and timing. There are some signs that some stubborn troughing across the Great Lakes/Northeast could emerge late in the month. While that’s not necessarily ideal for Plains severe activity, we are moving into the time of the year where that’s still workable. The last run of the Euro Weeklies hints at this, but still shows a general pattern that would support severe thunderstorm activity from the Plains into the Midwest. Those with trips or “chasecation” prospects should be encouraged by the signals. It’s already been an active year, but another active stretch appears to be in the works.

Targeted Northeast Texas and briefly caught a tornado about 7 miles NW of Paris, TX. Visibility was low for much of the chase, both due to haze and terrain. I could not confirm a ground circulation from my vantage point, but others closer could. It was also a bad area for radar data. Right in the middle of the TLX-SRX-FWS triangle. The picture is from 7:48 PM, when it was winding down.

Multiple areas to watch across the subforum region today. SPC has a moderate risk for a threat of very large hail and tornadoes across southern Missouri and vicinity. Convection is ongoing near/north of the warm front, as well as closer to a surface low, ahead of an approaching cold front. Watch the warm frontal zone across southern Missouri and perhaps far northern Arkansas for the greatest tornado threat later today. Here, low level hodographs are enlarged and both deep layer shear and instability are more than sufficient. Satellite imagery shows a few boundaries across Arkansas, but weaker large scale forcing and capping will be limiting factors. A few CAMs have hinted at isolated open warm sector development as well, so the threat is non-zero here. Early afternoon convection near the MO/OK border should expand and shift east. Additional development down the cold front is possible across eastern Oklahoma, although there is still some capping noted. Another area to watch is northeast Texas. Warmer mid level temperatures are in place, so CI should be delayed until late afternoon. Hodographs are elongated with less low level curvature. This combined with extreme instability suggests large/very large hail will probably be the main threat.

Right over my house. I’ll report back if we see anything noteworthy. Looks outflow dominant. Update: Saw several power flashes to the west (from Moore), strong wind gusts, maybe to 50 mph, small hail and lots of lightning, but that’s about it.

Just got home to Moore… but a very quick chase recap: Had a late departure from OKC at 4pm, but made it to NW Oklahoma as supercells were beginning to mature. I chased the northern OK supercell west of Enid for a while, but it just couldn’t wrap up. I then went south for a more intense supercell. It went tornado warned and produced a lot of lightning. It had a donut whole presentation on radar at one point, but I kept a distance due to the extreme chaser convergence and traffic. I watched the storm in a field near Marshall. Once it passed by, I had to call the chase off. There was gridlock eastbound toward I-35. I made it all the way to El Reno for the tail and supercell. It briefly looked like it might produce, but once I felt cool outflow surging, I bailed back to Moore. There’s a supercell approaching from the west, but I’m not particularly concerned, based on radar presentation. I haven’t read this thread since midday, but I’m assuming there was talk about the setup “underperforming.” I have to give the 3km NAM credit for having a pretty solid handle on convective evolution. It suggested that storms would tend to go linear. It also appeared that upper level winds were slightly more southerly than westerly, leading to storm mergers and linear transition. The more westerly flow is impinging on the unstable environment now, it was, perhaps, just a tiny bit too late to contribute to more discrete supercells. Also, the low level lapse rates from OUN seemed to verify closer to the lower NAM progs, which were probably a limiting factor. They heavily contributed to the underperforming nature of the last central Oklahoma high risk. Even 00z only “recovered” to 6.2 C/km. Marginally favorable at best. Anyway, I’m not saying the setup was a bust, but there are reasons why the highest ceiling wasn’t met. A few rogue supercells did evolve and embedded supercells continue to sustain a tornado threat, at least for the next couple of hours.

12z soundings… FWD highlights the boundary layer moisture that will advect north/northwestward: AMA gives an idea of the deep layer wind profile and EML advecting eastward through the day:

Broyles, but with Edwards. This morning it looks like the HRRR is slowly nudging a bit to the NW, which could be good for OKC. With that said, it also hints at a confluence band of storms attempting to fire by mid-afternoon, just west of the I-44 to I-35 corridor. Forecast soundings show minimal convective inhibition by 19-20z over central Oklahoma, so that’s plausible. The main action will probably initiate west of there near the dryline. It seems like there’s always a curveball or two, but we’ll see. I still think the northwest to north-central Oklahoma area is in ground zero, pretty much no matter what happens. It’s a little more conditional near and south of Oklahoma City. Hopefully the 12z suite gets into more agreement with details.

I don’t think they’re not making the decision to upgrade based on something like that. I distinctly remember that there were some caveats with that event in hindsight, most notably the poor low level lapse rates. Monday evening’s forecast environment is high end. Not the high end that we talk about once or twice a season, but more like the highest end we’ve seen in years around here. The 06z HRRR is about as ugly as a model run as I’ve ever seen for Oklahoma and I’m literally having trouble sleeping. 5/20/19 had the “swarm” of small supercells on the HRRR, but this is apples and oranges. The HRRR shows isolated, beastly supercells, no surprise given the background environment. I mentioned earlier that I’m having trouble seeing limiting factors in the environment. Only one model shows weaker low level lapse rates (3km NAM), but even that has seemed to have backed off. Analogs should be used with a grain of salt, but the synoptic similarities to 4/26/91 are legitimate. Two things are going to be key in determining MDT vs. HIGH risk tornado forecast/verification: 1. Where is the corridor of greatest tornado potential? HRRR favors the northern half of Oklahoma, while NAM/WRF models focus in on central to southern Oklahoma. It’s not a matter of if there’s a tornado outbreak, but where the outbreak occurs. Model biases are highlighting the south vs. north divide in the coverage of storms. 2. How many storms (discrete, long lived) are there? Given the background environment and WNW mean upper level flow atop a robust 50+ knot southerly low level jet, it’s a textbook supercell wind profile. Add in the subtle capping, timing of the wave, low level moisture and thermodynamic profiles and pattern recognition screams “tornado outbreak.” If you only have isolated convective development across Oklahoma, you can envision a scenario with a couple of long track tornadic supercells, much like a 4/26/91 type event. I pulled the 00z 4/27/91 OUN sounding and noted some warming around 700-600mb that probably contributed to the lack of sustained supercells with southward extent, effectively sparing the OKC metro area. With tonight’s event, I think just about every model at this point suggests you will get CI down to I-40… but, are the NAM/ARW solutions correct with more numerous CI, all the way down toward the Red River? I mentioned earlier about the NAM showing more of a clustered storm mode, but meteorology warns against that. (Upper level flow just about perpendicular to dryline, residual capping through mid/late afternoon, timing of the wave, etc.) With that said, the HRRR seems to be the outlier now with a dearth of CI across southern Oklahoma. Although the FV3 curiously also showed a lack of CI the south, which is both worrisome and a bit peculiar given the tendency for the model to over-convect. When you have a bonafide extreme environment and models only show sparse convective development, that’s an ominous warning sign that any storms that due form have a high likelihood to be strong/intense. At that point, you have to use meteorology and understand that the background environment is favorable over a broad area (much of Oklahoma). Going back to storm coverage, the NAM/WRF models show more storm coverage, including all the way down to the Red River with the 12km and 3km NAM. In my experience, given respective model biases, a compromise between the NAM and HRRR is going to get you a reasonable idea of what to expect. If you take the 06z HRRR solution of discrete storm modes and blend it with the NAM, which shows more convective coverage, including with southward extent, you probably have a high-risk caliber tornado outbreak over at least a portion of Oklahoma. Again, is the area of focus zeroed in on northern Oklahoma, like 4/26/91, or do we realize an outbreak that extends into and south of OKC, possibly down to near the Red River? That’s your difference between moderate and high risk. You’re not going to see the SPC go high risk for an 18-24 hour lead time for 2-3 tornadic supercells. If they’re a broader corridor that can sustain multiple such storms and if seems like we may be trending toward that, then you can see an upgrade to high risk. From a public awareness perspective, MDT vs. HIGH is almost irrelevant. It only takes one storm to change communities and lives. High risk is not something you should hope for, much like hoping/wishing for EF-5 tornadoes/damage. I’ve lived in Oklahoma since 2016 and I think this is the worst I’ve felt about a forecast in that time frame. I don’t know what else to say at this point. I can’t see much changing. We just need to nail down the coverage of storms and go from there. Hopefully the more intense storms take a track that causes the least amount of damage/destruction. This is ugly as well. Nighttime storms, long tracking, potentially near at least one metro area (OKC) and possibly multiple (Tulsa, maybe even Wichita?). Chaser convergence is already bad enough with any hyped up event in Oklahoma. Sure, at least we don’t expect the tornado threat to target OKC at rush hour, but it’s not like after dark is much better. I hope people, including chasers, take warnings seriously and that everyone stays safe and prepared.

I’ve had some time to review the 00z data and it’s not making me feel any more comfortable. The “trend” I eluded to earlier has stopped and we seem to be zeroing in with confidence on the probable outcome on Monday. CAMs continue to show a quick-to-linear evolution of convection across Kansas, but virtually every CAM shows at least isolated supercell development between I-40 and the KS/OK border area by late afternoon. Another observation is that multiple models show or at least hint at prefrontal convection as well, somewhere near or east of I-35 during the early evening hours. At this point, I’m grasping at straws to try to find some limiting factors… 1. The 3km NAM does show marginal low-level lapse rates ahead of approaching convection from OKC and points south. (Around 6 C/km) The bad news? Every other model, including the NSSL WRF, shows considerably steeper lapse rates. It may be related to a low level moist bias. 2. The NAM/WRF suite shows clustered storm modes, trending toward bowing structures around OKC. The problem? The wind profiles are much more supercellular in nature, so I’d take reflectivity progs with a grain of salt. Another peculiar note is that the usually convective happy FV3 shows very little CI across Oklahoma, in an otherwise extremely favorable environment. Perhaps it’s residual mid-level capping, which appears minimal at best by 00z. Almost any way you slice it, the setup has an awfully high ceiling across Oklahoma and vicinity. Even in the best case, where you have a bowing structure surging SE across the state, the expected wind profiles and strong/extreme instability favor embedded tornadoes. If convection remains isolated across Oklahoma, even with only a couple of cells, the risk of any of those cells producing significant, potentially long-lived severe is rather high. Then you have the worst case scenario, which is presented by some models, including the 00z HRRR: a broken band of supercells ahead of the dryline with pre “frontal” cells, all of which seem to mature around or after sunset, over or close to Oklahoma City. Reference the latest SREF convective probabilities, at 03z Tue (within the most favorable environment) and there are >40% probabilities of convection near and south of I-40, despite models showing a relative lack of CI in the area. (Convective precip > 0.01” with >2000 J/kg CAPE and > 30kts effective shear)

Models are trending faster with the lead shortwave ejecting across Kansas/Nebraska. In fact, guidance suggests that large scale forcing may reach western Kansas by 15-18z with early convective initiation. This solution causes a cold front to rapidly overtake the dryline. The result favors a linear storm mode across Kansas and possibly even into northern Oklahoma. Farther south is a different story. If you look at the 6z 3km NAM, notice how another belt of enhanced upper level flow stretches from New Mexico into West Texas. This flow is more westerly as opposed to southwesterly up north. The forcing across the southern High Plains/western Oklahoma area is later than up north, arriving closer to 21-00z. Forecast soundings across central Oklahoma in this time frame show residual capping as somewhat warmer mid-level temperatures are noted. This solution would delay convective initiation until late afternoon. With that said, forcing timed more favorably with peak heating, along with a westerly component to the upper level winds, suggests a more discrete storm mode. To quickly recap, the trend favors quick shortwave ejection across the Central Plains with a more linear storm mode there. There’s a split emerging in the flow across the southern High Plains, favoring a secondary, more discrete supercell thunderstorm risk over the Southern Plains. In my mind, the question is, does this trend continue? If not, the snapshot in time favors an ominous risk across southwestern into south-central Oklahoma and far northern Texas from late afternoon into the evening. It places Oklahoma City on the fringe of the greatest threat and the timing would likely fall just after sunset. Linear storm modes are favored to the north, while at least isolated supercell development is probable to the southwest/south. If the trend continues, you could see the primary threat area get booted down toward the Red River and northwest Texas. That would be better for Oklahoma, especially OKC metro. I’ll be watching trends closely today. I’m not a fan of the current progs, as they place a significant severe threat close to Oklahoma City, after dark. There’s not a ton of time left, so the next few model runs will be critical.

The synoptic look is there. Broad troughing across the central US and a steady conveyor belt of enhanced upper level flow ejecting toward the Plains/Midwest. The NAM/GFS show plentiful moisture with upper 60s/lower 70s dews on Monday through the ENH risk area. The Euro is tempered a bit, but still favorable for severe. Tuesday could be a volatile day from the Ozarks to the Midwest, assuming there isn’t significant convective overturning early in the day. A robust jet streak is progged to be aiming right at MO/IL with lower 70s dew points and a supercell wind profile from AR/MO into IL and vicinity. There is still time for the forecast to trend and evolve, but it’s looking like another multi day event is on tap.

Large buoyancy coupled with marginal deep layer shear and weak low level flow will support at least a few organized severe thunderstorms around North/Central Texas. The environment should feature rapid convective initiation by mid to late afternoon, albeit with a tendency for mixed/messy, HP storm modes. Dew points are averaging in the lower 70s around the ENH risk area. Temperatures will only need to reach the lower 80s to breach the cap, so storms may start developing as early as 3-4 PM. Surface winds are backed a bit with eastward extent, where earlier outflow is gradually modifying. I’m not sure about the tornado threat. It’s non-zero and will probably heavily depend on storm scale interactions. Heavy rain and localized flash flooding are also a concern.

A Tornado Watch has been issued for parts of the OK/TX panhandle vicinity, where convective initiation is underway southeast of Amarillo. Of course there was also a tornado reported near Fort Stockton, TX earlier this afternoon…

Today’s severe thunderstorm threat is focused from Kansas, southward into West Texas, where SPC has a narrow ENH risk outlined. A surface low is slowly drifting north across far southwestern Kansas with a dryline extending south-southwestward across West Texas. A warm front is draped east, in the general vicinity of the KS/OK border. A composite outflow boundary/moisture gradient is evident from the eastern Texas panhandle, then southeast across southern Oklahoma. Convergence and low level vorticity will be maximized near the surface low across southwestern Kansas. This is one favored area for isolated to scattered supercells by mid to late afternoon. The question here, is will storms stay in the narrow moist sector, or drift north of the warm front? DDC has seen rapid air mass recovery from the 12z RAOB, as the dew point was 60F as of 17z. The 12z sounding also featured an EML and moist mid-levels, suggesting further air mass recovery could put DDC on the fringe of the favorable environment later this afternoon. At least isolated supercell development seems probable to the south, across the OK/TX panhandles and west Texas. While the warm sector may be narrow in the northern part of the area, it broadens substantially south of the outflow boundary. 17z observations show 70F dew points as far north as CDS. The boundary may serve as a focus for increased tornado potential, given backed low level flow. Storm mergers and interactions may lead to a messy storm mode in this area, especially if convective development is widespread.

The HRRR really performed particularly poorly today for southwestern Oklahoma. It didn’t show any convection until the 22z run, while the NAM (and other CAMs) showed CI for several runs. As I type this, a Tornado Emergency has just been issued for Tillman County and surrounding areas.

Looks like a slam dunk for severe storms today up around the western Iowa/Omaha vicinity again. Some storms will probably develop southwestward into Kansas, but convective initiation across OK/TX is more uncertain. At least isolated storm development is possible, but I’m not sure I buy the more aggressive models with their biases. Tomorrow has a very interesting synoptic look. Weak, glancing forcing with sufficient deep layer shear atop an unstable environment. Early day convection across KS/OK may play a key role in where the severe threats wind up. The more aggressive CAMs show convection diving into Oklahoma, pushing an effective front/outflow boundary into the Texas panhandle/NW Texas, toward the Red River. The HRRR and RRFS show less convection, keeping the front over western to south-central Kansas. Watch where the boundary sets up. Does it sink into western Oklahoma? Or does it stay up in Kansas? The favored area for severe convection will be near the triple point, OFB/WF intersection. We’ll probably have a better idea tonight, based on model trends and how much convection forms with southward extent.

Oklahoma is going off. Turns out Nadocast wasn’t that far off. Maybe just a tad east of progs, since initiation was delayed a bit. We have what, 4 PDS tornado warnings at the same time in close proximity right now? Geez.

Radar confirmed tornado in Norman a short time ago. We dodged the worst of it in Moore, but it was a close call. Never totally count out the threat when parameters are in place and storms are still ongoing or initiating. It could have been worse, but this was bad enough.

OUN doubling down. The storms from NW Texas into the Red River area have meant business, but so far it’s looking like a big dud for central Oklahoma and the metro area. It’s not over yet, but I really didn’t expect radar to be this quiet.

Seeing a wide difference between the NAM/WRF/NSSL guidance and HRRR/RRFS from 12z. The former camp erupts a line of convection very quickly across northwest Texas, plowing into central Oklahoma with a mostly linear storm mode. On the other hand, the HRRR and RRFS runs continue to show discrete/semi discrete storm modes through at least early afternoon. That’s an obviously much more alarming scenario. Radar/satellite trends seem to favor more of the discrete mode with less storms through the morning. However, mesoanalysis shows minimal convective inhibition remaining across the NW Texas vicinity. Any way you slice it, today still has a very high ceiling. Even if only a couple of isolated storms reach their full potential. If storm modes do stay more discrete, it’s not going to be a good day.