Tornado Central

Well, the setup today didn't look too good, but it as good as anything we've had within a 5hr drive of Norman in the past several weeks. With the possibility that this would be the last chase of the season in OK, Gabe, Jana, and I headed up to the northwestern part of the state. We were originally targetting the OK / TX panhandle border region, but hoped on a southward-propagating supercell that traversed the extreme western part of Oklahoma this afternoon. The storm had intermittent supercell structures, but was also outflowish at times. We drove through hail at least the size of half-dollars (as the numerous dents in the hood and roof of my car will indicate), and we measured 69mph winds as well. Overall, it was quite a nice chase, despite the absense of any tornadic action. I have a more detailed report HERE, and I'll try to get one up on my website within the next couple of days.

Man oh man is this season not getting any better. Latest GFS and ECMWF runs indicate that a relatively high-amplitude trough will develop in the eastern US, with strong ridging across the mountains in the western part of the US. Oddly enough, I had been looking for some phasing of the polar and subtrop jets; this will happen it appears, but with a trough in the east. Ugh, I'm pulling my hair out here. There may be a couple of supercells south of I70 the next few days, but upper-level support will remain well to the north, so any supercell threat will likely be relatively short-lived or at least not very significant.

The odd thing is that this year looks like it will go down as an average year in terms of tornadoes. SPC Monthly Tornado Reports show that we are still well above the 10-yr average in terms of the number of tornadoes thus far, though we will likely return to normal as we will likely see fewer than a dozen tornadoes through the medium-term (couple of weeks). I absolutely cannot believe that we'll see significant flow aloft after this trough moves out, since climo would strong suggest that we'll get into the seasonal summer ridge south of I70. Of course, this year has been very aclimo, as evidenced by the intense drought and record high temperatures.

This also goes to show that good tornado years do not automatically make for good chasing years. Most of the tornadoes in March and April (which were extremely active by all measures) were east of the plains, across MO, IL, KY, AR, TN, MS, AL, etc. I thought last year was bad, but at least Ma Nature smiled on me a couple of times this year -- namely the 4-24 El Reno tornadoes, and the 3-20 "cold core" tornado in Dewey Co. OK. Beats 2005 for me.

The July-like pattern is continuing, and all signs indicate that such a pattern will persist through the early part of June. This, largely, is the reason why my blog entries have dropped off to a two-a-week occurrence. Strong ridging will develop and persist across much of the central US, with the jet stream heading north into the northern Plains and southern Canada. Latest model indications suggest that the various western US troughs that will be present through the next 10 days will not be able to make much headway eastward before sliding northward or northeastward on the west side of the ridge. The subtropical jet does make an appearance across OK and TX through about 60 hours, before shifting southward into Mexico. There may be a few rogue supercells off the dryline on Saturday across the central and southern Plains as a strong lee cyclone develops well to the north, with impressive LLJ underlying southwesterly (yet weak) flow aloft. In terms of an organized, sustained supercell threat however -- that will be hard to find south of I80 (perhaps even south of I90, and I94 at times). I continue to have very little hope for any significant tornado days south of I70 through the medium-term (mid-June). It's been quite some time since we had a significant tornado event Kansas after mid-June (6-12-04 and 6-12-05 seem to be the latest significant tornado days lately), so that may effectively mean that the spring chase season for the southern plains is largely over... I suppose there may be a couple of west Texas or eastern NM setups, but the death ridge is knocking, and Ma' Nature is heading for the door.

That said, for those folks fortunate enough to live near or north of I70, it looks like it may be a very active chase season, with the main threats remaining north of I80. Hopefully we can beat this ridge down in a couple of weeks, if for no other reason than the need for rainfall. Short-term drought conditions have yielded a bit east of I35 courtesy of the rainfall the past 6 weeks. However, areas west of I-35 largely missed out on those rains. Regardless, the long-term drought persists for much of the area, with locations in eastern OK down about 16" relative to the 1-year average. Of course, given how we really haven't had a lot of good chasing within about 4-5 hours of OUN this year, I wouldn't mind a few good chase setups. Looks like I may need to take a few >1000-mile trips if I want to get my fix.

I'm still on the fence about tomorrow, but I'm putting my 'chase probability' at 60%. 0z soundings from the Plains indicate that moisture depth is no longer a big issue, but the overall magnitude / quality of the moisture is still questionable. In addition, I hate chase days in which the shortwave or jet max aloft weakens with time, which is what we'll see tomorrow. There have been many other good tornadic supercell days with only 30-40kt 500mb flow and 35-40kt 0-6km shear (e.g. 5-12-04, 6-12-04, 6-12-05, etc), but almost all of those days also feature strong to extreme CAPE (e.g. >3000 j/kg). Unfortunately, without true tropical moisture, and 500mb temps that won't pass as 'cold', we probably won't see such high instability tomorrow.

The 18z NAM-ETA looked very nice for tomorrow, with a frontal zone from southcentral NE into northern KS. This feature, however, is non-existant on the 0z NAM-ETA (as it was on the 12z). The low-level flow looks fine, and the hodograph curvature is nice. The marginal flow aloft may yield deep-layer shear profiles that border between multicell- and supercell-favorable.

The longer-term prospects (though Day 10) don't look all too good south of Nebraska / I80 or east of I25 (in far western TX), so I'll probably bite. Latest GFS continues to pump up the central US ridge downstream of a couple of west-coast troughs and cut-off lows. Tonight's run does show a phasing of the jets in the base of a western US trough during the middle of next week, but the strong, high-amplitude ridge in the central US and Canada has a tough time moving much, leaving shortwaves no option but to ride north or northeastward into the far north-central part of the US. The subtropical jet may give some action to western TX and eastern NM again (like we saw several weeks ago in the CDS-ABI-SJT-MAF-Roswell-LBB-CDS area).

Possible chase day Tuesday. Moisture is still the main concern, with the 0z CRP and BRO soundings still not putting a big smile on my face. Current observations indicate upper-60s and a few 70-71F tds down along the Texas coast, so the good moisture may finally be making it back onto the land after getting wiped last week. Buoys in the western Gulf are now reporting 71-73F Tds, but the depth of the quality moisture is not possible to know over the Gulf. The GOES sounding for 25N 95W (which is ESE of BRO) indicates that the good moisture is only about 25-30mb deep, though even that is a little shallow compared to coast RAOBs. Regardless, we have 36-48hrs to get deep moisture northward about 1000 miles.

Is that going to happen? That's a very important question. If not, I don't think CINH will be breakable, leaving chasers under a hot sun getting burned. If we can manage to get the moisture northward, with some evapotranspiration help, we may see a few storms develop on the dryline by late afternoon. The 0z NAM tonight depletes the CINH north of McPherson KS, largely due to it forecasting >65F Tds up along the dryline (compared to 60-65F Tds along the dryline by 0z that it showed on this morning's run). The timing of the shortwave and vort max looks to be quite nice, with the 0z NAM indicating the leading edge of the vort max very near the dryline at 0z. Strong wind fields will characterize the low-levels, but upper-level flow is a little lacking. Such a wind profile is showing only about 30kts of deep-layer shear, which is on the low-end for supercells, particularly for only 2000-2500 j/kg sbCAPE shown on the 0z NAM. The low-level shear will help yield a tornado threat, but the climatologically-low CAPE and low-end deep-layer shear isn't going to help any. But hey, at least the GFS and NAM are both showing the vort max affecting all of Kansas, which contrasts with a few previous runs of the GFS and other models, which had the vort max no south of South Dakota.

Given the past 2-3 weeks, I'll probably head out, though I'm not sure how much I'll be expecting. The oven has been on over the western and central US the past week or so (OKC broke a record high Friday, and tied the record high Saturday, with a slew of >100F temps just west of I35), which is leading to hot 850mb-700mb temperatures. Typically, when this is the case, we really do need true Gulf moisture in order to give us a good chance at surface-based convection. I'm not entirely sure we'll be able to get that north of I70 by Tuesday, and the poor performance of the operational models (WRF included) certainly does not help much either.

Since I have very little faith for chase prospects south of I70 or even I80 the rest of this spring, I'll probably head towards Concordia or Hebron on Tuesday. With the heat that we've had the past week, cap issues will be significant, and with the polar jet at such high latitudes recently (though, I find it interesting that the subtropical jet has remained steadfast through Mexico lately) it looks as though we skipped from March to July. Maybe we'll get some phasing in the upper-level flow by the weekend or next week, but I have no faith in model forecasts out that far.

I wish I could take a dose of sweet optimism to help cure my chasing blues, but the overall pattern (and a cursory look at the 18z GFS) gives me little reason to think there's much in store for areas south of I80 with models indicating that the main belt of the westerlies will stay across the northern plains through the rest of May. At least we got some action in early June last year, so I'm still keeping my fingers crossed. I am, however, quite bitter, and feel like a child wishing to rebel against Ma' Nature. Unfortunately, there's not a dang thing I can do about it, save to rent an RV and move up to the northern plains for the next month or so. I do, however, thoroughly hope I am wrong.

What is the garbage some of the models are showing?! Southwest flow aloft? More classic severe weather setups possible by next week? Time to smack mother nature to remind her that chasing is supposed to be over with for this month. LOL Just kidding, of course. The pattern that we've been stuck in courtesy of highly-amplified and blocked upper-level flow (we had two blocks in place several days ago -- a moderate Omega block across North America, and a high-over-low / Rex block across the eastern US and eastern Canada). Regardless, this should give way later this weekend and next week, with some indications that we will see zonal or southwesterly flow aloft. This, as is typical, will induce lee troughing, aiding in northward moisture transport. The Gulf has been raked several times in the past 10 days, so the quality of the moisture is yet to be seen. BRO, LCH, and CRP soundings continue to show seasonably dry low-level moisture profiles, which is not surprising given the FROPAs from the past week or two. Buoy 42055, located very near the Bay of Campeche, is only indicating a dewpoint of 57F right now, a full 18F degrees lower than last weekend! Farther to the southeast, buoy 42056, south of the Yucatan - Cuba pass, is currently reading a dewpoint of only 69F. The latest frontal passage is clearly evident in the dewpoint traces from both of those buoys. Ugh.

We shall see. I still have significant hesitation regarding how much faith I'm putting in these forecasts, since consistency could be quite a bit better. But hey, it's a start, isn't it?

Whew. Finally done with the spring semester. I've been busy the past week, so I haven't had much time to blog. The 10-day forecast is about the absolute worst one could see for this time of year (May), with a very high amplitude east coast trough and cut-off low. Current model forecasts shows a high-over-low block developing from the eastern US into eastern Canada very soon (there is a semblance of such a block now). In addition, as the ridge intensifies across the western US, we will likely see an Omega block situation develop, with high-amplitude upper-level troughs over the eastern Pacific and the eastern US. It's quite unfortunate to have one blocking pattern in place if we're on the less favorable side of the trough, and it's doubly unfortunate to have two blocking mechanisms. All signs, however, point to the east coast trough persisting for at least the next 7-10, with the HPC hinting at the possibility of this blocky pattern persisting through the end of May.

Typically, northwest flow aloft provides occassional chase setups across the western high Plains and southwest Texas / eastern NM. However, these setups are much more common in June and July, when ample boundary layer moisture yields significant instability. As it stands now, the trough is close enough to us, and the flow is strong enough, that we'll see several respectable high pressure systems build down out of Canada (following decent cold fronts). Models indicate that the Gulf will get FROPAd at least once, and most likely twice in the coming 10 days, leaving the Plains starving for moisture. Of course, there may be a mesoscale-setup here and there through the 10-day period, but the chances for any significant and/or large-scale setup seems very remote. West Texas did very well a couple of weeks in, in generally weak flow aloft and moderate low-level moisture. Granted, there wasn't a whole lot of tornado action, but supercells were abundant. Actually, tomorrow looks like it would be a decent setup if we had Gulf moisture in place across southern OK and northern Texas. Strongly veering winds will create favorable shear for supercells and possibly tornadoes (looking at low-level shear forecasts), but the lack of substantial and deep moisture will prohibit the development of significant instability, and it may inhibit surface-based thunderstorm development to begin with.

If someone had given me a pen and paper, and told me to draw out the worst possible synoptic flow pattern for May, I couldn't draw it much better than what we will see through next week. Ugh. Models are giving us a little hope beyond the 10-day period, but that's well, well into wishcasting territory.

I've been studying for a Convective Clouds and Storms final that I have on Tuesday (imagine the coincidence should that turn out to be a chase day!), but I did want to mention that it looks like I may have to dart out after my exam (ends at 3:30p) given how things currently look. With true Gulf moisture in place, strong to extreme instability should develop by afternoon. My main concern right now is that the OK and n TX area (along and north of a strong dryline bulge progged by the models) is forecast to be in a coupled-jet scenario. What, why is that bad? When we typically use "coupled-jet", we use it to describe cyclogenesis or precip enhancement from the combined ageostrophic circulations found in an area that is under the left-exit region of one jet streak and the right-entrance region of another jet streak. However, the upper-level pattern for Tuesday looks as though we may be on the other end of a coupled-jet -- the right-exit region of a jet streak coming from the northwestern US and the left-entrance region of a jet streak along the Gulf coast. Each of these quadrants is characterized by large-scale subsidence (via transverse circulation), and being in both quadrants is doubly-bad. Winds aloft aren't spectacular by any means, but the directional shear should be quite favorable, and, given the strong to extreme CAPE, tornadic supercells may be a strong possibility. I just hate chasing in areas which are experiencing large-scale subsidence...

On a non-chasing note, I read through a very troubling and emotional book tonight -- One at a Time: A Week in an American Animal Shelter, by Dianne Leigh and Marilee Geyer. The book is blunt in making sure we know the truth about animal euthanizations and the severity of the animal overpopulation problem that we face in this country. It's wholely heartbreaking to read some of the individual stories, and entirely infuriating to read about why many of these animals are put in the predicament they are in. Some animals are given up because they have minor behavioral issues, despite the fact that (per the book) more than 90% of the animals given up to that particular shelter have had no training whatsoever (apparently, people think dogs will just learn not to bark, or will learn how to wait at the door if they have to go 'to the bathroom'). Others are given up because they just aren't wanted anymore. Regardless, I recommend the book to everyone. It's about 140 pages, but there are numerous of full-paged pictures, and the book actually read more like a 'coffey-table book' than anything else. It isn't gory or anything, and it is pretty well written. You don't need to be a "animal-lover" to take away a message from this book either. All life is deserving of respect and dignity, especially for those whom we purposely bring into this world.

The local Fox affiliate did a story on the OKC animal shelter a couple of months ago. I liked the piece, though it was disturbing to watch numerous healthy, perfectly adoptable animals get euthanized (a nice way of saying killed) solely because they needed the space in the shelter. Hundreds of pets, rubbing up on the shelter employees until they realized there ultimate fate. After euthanization, they get throw into a garbage bag, then dumped in an area landfill. Nearby, breeders are bringing more pets into this world, and pet stores are selling animals to more unfitting people. While some shelters kill hundreds of healthy animals per day, people continue to breed new animals, many destined for the same terrible fate. Why we see a need to bring new animals into this world when we kill thousands each day is beyond me. Many shelters get purebred animals occassionaly as well, so shelters are far from places reserved only for those animals who are misbehaved, uncontrollable muts. Sad, very sad.

We have made dogs to be our most loyal friends, and they live that role, to the very end. And so they go willingly, with trust. They cooperate when the leash is hooked to their collar, and follow obediently on the last walk they will ever take. She didn't know what would happen to her, but she went. Willingly. With trust... a trust betrayed first by the family who lost her, and then again by a society who can do no better than offer this as their answer.

-- p. 75 - One at a Time: A Week in an American Animal Shelter

Well, there have been several impressive supercells the past couple of days across western Texas. Yesterday, there were a pair of nice supercells down near and in Kent county TX (east of Lubbock). So far today, there have been several impressive supercells from east of San Angelo to southwest of Lubbock. The supercell in Gaines county was very impressive in terms of strong low-level shear and awesome hook echo. Others have had decent low-level couplets tonight, but the size of the hail seems to be a bigger threat than the tornado threat right now. The cell just west of San Angelo has had numerous reports of 4.25" hail (that's between grapefruit and softball size), and I see that the cell near Abilene also has confirmed 4.25" hail with it. The 00z MAF sounding showed considerably stronger deep-layer shear than we've seen the past couple of days (~50kts 0-6km), courtesy of 30-35kt westerly 500mb flow atop 20-25kt easterly 850mb flow. Throw in very backed flow along the OFB, and you have a recipe for strong supercells.

As has been the case the past several days, the 36hr forecast looks good, but the target area shifts southward with each successive model run. For example, the 12z Weds NAM run got me excited about a north Texas chase today... Lo and behold, the organized squall line yesterday pushed the effective front / OFB south of I20. Likewise, the 12z NAM foreast from this morning got me excited about a potential chase in western north Texas (or east-southeast of LBB) for tomorrow. However, the 18z and 00z runs have continued to push the threat farther southward. I'm willing to head as far as Sweetwater, but that looks like it may be on the very northern fringe of the significant supercell threat tomorrow. So, as it stands now, I'll probably sit this one out (again). Models have generally performed quite poorly the past few days (as is typical in a pattern such as the one we are in now -- heavily influence of nocturnal convection, weak waves aloft, etc), so I'm still crossing my fingers.

The medium to long-range GFS forecast certainly does not bring up my hopes any either. This morning's 12z GFS run indicated a significant trough digging into the eastern US by the end of next week, with a strong (and cold) high building down out of Canada in an area of very strong northwesterly flow aloft upstream of the trough (in the region of strong ageostrophic curvature convergence aloft and resultant large-scale subsidence). As it stands now, it looks that this solution may lead to the Gulf getting completely wiped by next weekend. Fortunately, I just mentioned how the 36hr forecast isn't so hot, so I certainly wouldn't take a 7-10 day forecast for much. However, the GFS has been consistent in developing a mean east-coast trough by the end of next week (and it has support among many ensembles). If this should verify, the hopes of a significant supercell chase north of I20 may have to wait until at least mid-May.

Fortunately again, however, the ECMWF does give some hope next Tuesday, with a strong upperlevel trough digging into the Rockies and yielding strong, diffluent southwesterly flow across much of the Plains. As long as we don't continue to get convection in central and southern TX to impede moisture return, we could get a decent chase out of such a setup. The rather strong cut-off high in the northern Pacific and split-flow across the CONUS is reaking all sorts of havoc on our upper-level situation. This certainly does not look like a "normal" May pattern. Perhaps it resembles 2005 a bit, if I recall correctly. While I'm quite pessimistic about any significant outbreak setup between now and the middle of May (maybe later if the Gulf gets hosed like the GFS suggests), it is very important to remember that predictability is quite low right now, so any 5+ day forecast should be taken with a big dose of suspicion. In addition, there could be a couple of more mesoscale-driven events (e.g. NOT the big synoptically-evident setups), which is just fine with me as long as it's within range.

Why can't every year be 2004? I guess I had 4-24-06 (El Reno tornadoes), so I'm doing better than 2005. :/

Tough call today. Before anything, it's extremely important to point this out:

SPECIAL NCEP DISCUSSION
CENTRAL OPERATIONS/NCEP/NWS/WASHINGTON DC
1310 UTC TUE MAY 02 2006

021310Z...NCEP 12Z MODEL CYCLE. NCEP PLANS TO START THE
12Z NAM 40 MINUTES LATER THAN NORMAL WITHOUT ANY
CONVENTIONAL OBSERVATIONAL DATA. WE WILL RUN THE NAM IN A
FASTER THAN NORMAL MODE SO THE NAM MODEL SHOULD FINISH CLOSE
TO ITS NORMAL TIME. THE NGM WILL BE RUN ABOUT 40 MINUTES
LATE. WE WILL SOON MAKE A DECISION ON THE START OF THE
12Z GFS.

(Thanks to Kevin Sharfenberg on ST for pointing that out)... Unfortunately, since later runs often use forecasts from previous runs as 'first-guess' fields, any errors in last night's 00z run will propagate farther into the future than would otherwise be the case. I'm not sure what's causing the problem, but it's a bad time for that to go down given how active this week appears.

I havent' had much time to do an analysis, so I can't really offer much in the way of chase forecast or plans. Today is up in the air, given that I have a lot to get done and the legitimacy of the setup is in question. I'm not quite sure I'd go 10% hatched tornado probs like the 13z Day 1 outlook shows, given the high LCLs (at the very least) that we're likely to see today. High CAPE can compensate for a lot of things (relatively weak flow aloft included), but the high CAPE days that produce tornadoes tend to still have relatively low LCLs (or at least not high LCLs) and substantial low-level shear.