Friday, April 29, 2005
We broke off around 0z and had dinner in Helena, on the Mississippi.
I considered beginning a longer chase trip with today, but since I'm having some a vehicle issue and the pattern looks weak at best for next week, I'm heading back to Indiana until the Great Canadian Pinwheel buys a calendar and gets out of our lives.
In Scott's defense, he was headed for Ohio to visit family and was chasing on the way.
All this serves to push our warm sector further and further south, so that now I'm hoping we can develop something in the area from LIT to Helena to Arkansas City. I don't know jack about that terrain, but I have heard there are pine forests somewhere down there in southern Arkansas.
Hopefully this surface low will get moving--it's been in north Texas now long enough to have taken on the scent of the Mighty Curse. We need it to put some vigor in our southerly flow, move the front, and make some kind of stand against the sagging cold air.
It's very early in the day, obviously, so a lot can change, but I feel like the tornado potential has decreased and the possibility of the cap holding for anywhere other than directly on the boundary is higher. With such a sharp temperature gradient, I'm less certain how beneficial that front will be if storms move immediately north into significantly cooler air. Hopefully it will stall and we'll see more diffusion there.
I'm still in Forrest City and will remain here a little while, conserving gas and making the most of a high speed connection. By 10:00 AM or so, I might cruise down 40 towards LIT and maybe drop south to Stuttgart, which looks to have some fair road options.
eastern strip of the state where there are allegedly pastoral stretches of chaseable farmland and pristine tornado hunting grounds. I'm luck to have the chance to chase with a few folks who know the place.
Since I have to go to sleep right now, I'll copy what I posted to Stormtrack moments ago:
"I still have hopes for this setup and believe it will produce a few tornado reports and a large number of wind and hail reports as well.
I agree with Rich that the slower, weaker shortwave is a great help in our case, allowing more time for the warm sector to juice up and destabilize (though the part that counts is really only the swath of chaseable turf on the eastern side of the state), and reducing the massive forcing we saw in earlier runs that had us all guessing about how quickly we'd transition to linear. I think that because of the less vigorous kinematics, stronger cap, and some indication of subsidence aloft (sometimes a bad thing, sometimes just what you need!), that we have a much higher chance of discrete convection for more than the two hours I was hoping for earlier. On top of that, our storm motions have slowed a little, which means the storms could potentially fire, mature, and produce tornadoes before they leave the eastern seaboard of the CONUS. :-)
I like the I-40 corridor from Little Rock to West Memphis, and fifty miles either side of that line.
Anyway, the warm front tomorrow is progged further south, and winds in and around it remain backed longer than on previous runs yielding 0-1k ambient SRH values over 300 m2/s2 in areas where one could reasonably argue storms might reach. 3k SRH is even higher, around 350 m2/s2, a nice signal that supercells could be the favored mode for longer than expected. We weren't looking at those sort of values before because of the speed and strength of the various features aloft and surface.
There's all sorts of downside potential, too, like cloud cover associated with an advancing 850mb warm front that outpaces the surface boundary, as pointed out by a friend of mine, the Mexican smoke Rich mentioned, or the simple unraveling of the whole show if the shortwave comes out even slower and weaker than the 0z NAM depicts. Who knows?
But it seems that tornadoes aren't always about bombogenesis and negative tilt crashing shortwaves with MDT risks and dancing bears. I think there' s a chance again early next week that we could see more setups where a subtle balance of ingredients yields chaser joy in small doses."
Wednesday, April 27, 2005
Storm motions transition from ~30 knots around 18z to over 50 knots by 0z as the sfc low zips off to the Ohio River Valley, courtesy of the Great Canadian Pinwheel that has brought winter back like some bad 70's retro tie-die t-shirt.
I think the mode will transition to linear around 22z, depending on the true speed of the system. With this system, because of the overall pattern, I don't think the model is too fast as I normally would. However between 18-21z, as the warm front is lifting into N Arkansas and the MO bootheel, co-located with ~2000 j/kg and 250 m2/s2 0-1k SRH and 60 knots of deep layer shear, I think supercells and tornadoes appear likely.
The warm front provides some basis on which to choose a target. It's conceivable to position such that you observe storms as they approach and cross the front, so that in a way you're not chasing storms as much as the boundary.
The Missouri bootheel is 300 miles from me, which means a one day chase if I wanted. It doesn't have to be the start of my vacation, so it makes more sense--if any of this makes sense at all. Since I'm already ready to chase for a month, I'm pretty well ready to chase one day, too. I'll see what it looks like tomorrow.
Tuesday, April 26, 2005
Since my last school-related function on Saturday night, I've spent a ridiculous amount of time scrutinizing computer forecast models and I have to reign it in. I composed some guidelines for myself that should help alleviate SDS at its very worst--right before a big chasing trip--and help me reclaim my life between now and whenever I actually begin the journey into Tornado Alley.
1. No more GFS. One of my favorite things about the 2003 and especially 2004 chase seasons was that there was no time or cause to scan the medium-range progs. You had a chase right in front of you daily, and tomorrow would take care of itself, not to mention next week. It's a great stress reducer to limit the number of setups you're analyzing simultaneously. To ease the transition, I'll look a little more at the UKMET and ECMWF.
2. Check the NAM at specific times only. I plan to spend thirty to forty-five minutes looking over things between 11:00 PM and midnight, then write something up after that. Probably the same routine in the mornings, though I'd like to eliminate that entirely. I suppose I could look at the GFS only as far as its available between these times, but I won't keep myself awake until 1:30 AM waiting on the magical 264 hour solution.
3. Wait for my pitch. I'll go chasing when the NAM shows a system that has a 5% to 7.5% chance of producing tornadoes along or west of the I-35 corridor. Until then, I'm going to live a normal life.
The perfect display is at 48 hours, when 850 winds in the plains back to a southerly orientation temporarily, only to fall back under the northeastern influence immediately afterwards and veer like mad. This has dire results for the orientation of the instability progged to work into the plains, and, on the best looking setup--Thursday--a double-barrel surface low forms, caught between the competition of a strong jet nosing into the plains on zonal flow aloft, and that damn New England storm.
My feeling is that I should wait until we work out from under that feature, since the longer range output is still positive, with persistent height falls associated with a southwestern US trough in the 180-224 hour range. This has shown up for so many runs now that I've lost count.
I'm not thrilled about this as I've made all the arrangements to leave for chasing sooner rather than later, and now it looks like I'll be standing down for a few days at least.
Monday, April 25, 2005
132 hours on today's 12z run, the GFS shows a positive tilt axis to the shortwave, with wind fields below that level extremely veered, and a cold front sweeping through the warm sector.
Like I've said before, you can't take GFS solutions too literally, but as they grow closer--particularly when they cross what seems to be a "magic" line of around 144 hours--you can begin to think about the details, and the details here are troubling. Since there isn't much behind this system for a few days, I have to admit the possibilty of delaying a few days or even a week, though I continue to prepare for chasing this weekend.
Monday, April 18, 2005
makes a fine argument for Colorado on Wednesday which I buy into completely. If I was already out on my vacation, I'd be all over the Front Range and DCVZ, my second favorite chase turf behind the panhandle. Eastern Colorado has the upper level support other areas are missing, and it has the golden touch of elevation and orographic lifting. I suspect Tony will have some great looking photos come Thursday morning.
But with only 12 days (12 days!!) before my May-cation, it's hard to plan another out-and-back excursion into the plains. They are exhausting, expensive, and mileage-intensive trips. If this were April 26th or later, I would be tempted to start my vacation early, though that could jeapordize June. What a weird liminal space--caught so close to my chase trip that I can't justify chasing.
Some will argue for the central plains where CAPE is impressive and I don't discount them because it is not impossible for tornadic storms to occur in weak shear environments when high CAPE is present. But I'm always suspicious of what I call "exception-based forecasting," where the argument begins with, "Well, remember that one time there was a wedge with only 100 j/kg SBCAPE and 500mb winds of 4 knots??!!" Obviously I'm making a silly example, but as a disciple of climatology, this kind of logic is like nails on a chalkboard to me, since the irresistible rejoinder is, "Yeah, and remember the 1000000 times that NOTHING happened under those conditions?"
I'm so suspicious of this kind of wishcast that as soon as somebody asks me to recall a specific event, I begin to question the setup. In atmospheric science, it seems to me, anecdotal evidence is particularly unimpressive, since in such a wildly complicated system so many variations and outcomes are possible. In other words, you can find an anecdote to support almost anything, and if that's what you're doing then there must be some major flaws with the setup you're trying to promote.
A studied and analytical approach to forecasting remains vigilant against outlier histories and does not give them more than their due, in my opinion. So I say things such as 'yes it's certainly possible,' and nod and smile politely. And there could be an angry unicorn on the dark side of the moon, too.
All that is to say I think tornadoes are possible where the CAPE max is both Tuesday and Wednesday, but I can't drive 1000 miles in hopes that another exception to baseline tornado climatology will occur, or that the models are wrong (more likely). I have to wait, only another handful of days.
Sunday, April 17, 2005
case study on the April 10th cold core event. This is essential reading.
Saturday, April 16, 2005
I don't like the trend on the last two runs, taking the system much more north and weakening it considerably. Low level wind fields become very weak and messy, and messy isn't attractive right now with my full chase vacation about two weeks away. I would much prefer not to chase, in fact, until I leave for May, since these long drives to and from the plains are expensive and inefficient.
Unless we have a real powerhouse setup move ashore, or next week's setup shapes up more promisingly, I'll likely stay put.
Friday, April 15, 2005
The 12z NAM and last night's GFS both forecast the split flow pattern over the CONUS to merge beginning early next week in a pattern that could make for several days of highly productive chasing. The key to this pattern is the lack of a single, high-amplitude system that crashes through and drags a front across the boundary layer; instead we have a progressive series of smaller waves that kick off storms but leave moisture fields intact so that we can wake up the next day and do it all over again. Some of us call this the "rinse and repeat" pattern, and one of the best places on Planet Earth to experience this is the Texas Caprock, which looks like a prime candidate for serious supercell action next week.
You may remember the caprock is an elevated section of very flat land, also known as the Llano Estacado, that stretches across Texas and New Mexico and acts as an orographic lifting mechanism for storm initiation. Because of the elevation--some areas of the caprock are above 4000 feet!--you don't require the 70F isodrosotherm to hug the eastern boundary of the dryline. This is similar to how eastern Colorado can see supercells and tornadoes with dewpoints in the lower 60s. Also, some forecasters believe that the canyons east of the escarpment may channel inflow and increase values of storm relative helicity to storms moving out over the plains, but this is highly theoretical.
For next week, the GFS shows a dryline making camp on the Texas/New Mexico border and daily mixing east into increasingly deeper moisture. This pattern begins on Monday and lasts through the week. With consistent southeasterly flow up onto the caprock, and westerly midlevel support for storm ventilation, this is the best setup for supercells in the Texas Panhandle that I have seen since mid-May 2003. Of course it's several days away and subject to radical change or complete disappearance, as we have seen so often before. But I'm not as interested in the details (what happens on which day) as I am in the trend and the pattern suggestion.
The NAM this morning begins reflecting the GFS with fair agreement, placing the first strong wave over eastern Oregon and preparing to swing it down across the Rockies. Since I was able to expedite my school obligations, I should have the chance to chase this system.
Wednesday, April 13, 2005
I still don't know for certain what day in May I'll leave to chase, sometime between the 1st and 9th, probably closer to the 9th. GFS shows nothing of interest for the next week, thank God.
My pal Tony Laubach has a cool picture of my truck on his blog, taken from the ABC-Denver clip that ran featuring his video. Tony had a great chase day on Sunday as well.
I'll update when I post those new reports.
Saturday, April 09, 2005
I think the Texas target is a good one, too, but it has some worries with the potential for veered surface flow and late initiation waiting until the strongest forcing arrives and increasing the chance for a quick squall line.
I was headed for Enid but turned around and came to Woodward instead. Makes sense if I'm headed toward Liberal tomorrow.
Good luck, everybody!
anything to go wrong, it's today--and things are
already going wrong.
The low in Colorado has divided, sort of, with a
secondary low further east than projected which is
backing the winds around Woodward. Too bad, because
the dewpoints were getting interesting up there. SPC
Meso site showed Alva at 59F dp last hour, though the
mesonet never showed that.
However, the new surface trough structure creates kink
currently in southwest Oklahoma that should move north
as these lows consolidate (with hopefully the
westernmost sfc low in colorado ingesting the
secondary low), and so I expect a new area of moisture
pooling to develop along this bend in the pressure
I'm stopped at the intersection of I-40 and 270
waiting for a while to see how this plays out. I'm
very conscious of not wasting gas, since I want to
chase both of the next two days also. Still, when I
made it west of El Reno, where the landscape really
opens up, I had a chill. There's no place like the
plains and that sensation alone was worth the small
amount of gas I expect to use for the rest of today.
Today I find myself in an unusual situation where tomorrow's target is influenced by possibilities both on Monday and even today. Normally I like to chase one day at a time and "chase the storm you're on," which is our way of saying sufficient unto the day is the evil thereof. However, if you chase in Seymour, Texas on Sunday, you're not going to make the surface low setup in northern Kansas on Monday unless you huff it all night, as we did the night before May 4, 2003--and I doubt the journey is anymore fun now than it was then. Not to mention that none of these setups are worth breaking one's neck over. But let me put tomorrow and Monday aside for a moment and talk about today.
Today is a bust waiting to happen. Today is dry, capped, with only modest convergence along the dryline and nothing spectacular aloft. However, there is the smallest chance that a single storm could fire on the dryline, and evidence already this morning that the models are underforecasting dewpoints in a developing area of moisture convergence in the northwestern areas of the state, between Woodward and Enid, for example. There is also a persistent band of high level cloudiness up there which is casting a relatively stable shadow in that same area, creating the possibility of a thermal gradient of some sort along the surface. This is all highly speculative. The cap, again, is very strong, and not likely to break.
However, if it did, the storm would almost instantly be supercellular and isolated, albeit high-based. Therefore the SPC dedicated a full paragraph to the area they didn't even outlook for slight, and the Norman Hazardous Weather Outlook describes the setup extensively. This is what we mean by a highly conditional chance of storms. Storms are unlikely--very unlikely--but if one formed, it would certainly be severe. Seeing the pooling moisture, the possible baroclinicity at the surface underneath the cloud band, combined with northwest Oklahoma's proximity to a favored target region for tomorrow near the low, compels me to amble up toward Taloga and Woodward, and work on my tan.
I'm in Moore, Oklahoma currently and plan to leave within an hour for higher dewpoints.
Thursday, April 07, 2005
Anyway, it's enough for me to see a trend like this, so I'll leave bright and early for Oklahoma to have position for chasing Saturday or to visit friends in north Texas (probably the latter), then for the big show Sunday, and what may be quite a followup in the Midwest on Monday. We'll see how it plays out.
Probably no morning update from me as I'll hope to be on the road by 8:00 AM.
AFD from Tulsa released a short while ago: "LOOKING AHEAD INTO SUNDAY...SEVERE WEATHER APPEARS MORE LIKELY AS MODELS REMAIN CONSISTENT IN SHIFTING STRONG UPPER LOW INTO THE TEXAS PANHANDLE BY SUNDAY AFTERNOON. SYSTEM LOOKS VERY SIMILAR TO LAST SEVERE EVENT WITH PLACEMENT OF UPPER LOW AND JET DYNAMICS. WILL DISCUSS FURTHER IN HWO EXTENDED CONCERNING TIMING...ETC."
SPC Day 3 showed a 5% chance of something out on the high plains after 0Z perhaps. I suspect they will drop that entirely if the evening runs confirm the meager moisture and lack of low-level definition. Saturday looks completely benign.
Sunday's solutions just posted for 12z GFS and it looks like a carbon copy of the last system which resulted in a squall line ahead of the boundary and some cold-core tornadoes behind the low. Very frustrating to once again find myself again having to make a decision sooner than would be optimal given the character of this system and the moisture questions. I don't feel good about this morning's runs as a justification for spending $200 in three days. On the bright side, the system is only now coming ashore and tonight's runs (and the morning's) should have a superior handle on the nature of the storm.
I'll go about my day and wait for the local offices to post their afternoon AFDs. I'm reading Herzog by the great American novelist Saul Bellow, who passed away a few days ago and whose death was overshadowed somewhat by coverage of Pope John Paul II.
Tuesday, April 05, 2005
Tony Laubach suffered some engine problems in Kansas very early this morning preparing for today's chase, so here's sending out some positive engine vibes to Tony and his chase partner Verne Carlson today. Since its an alternator, the guys should have no trouble recovering from the setback in time for today's storms in Kansas.
While I still prefer areas of eastern Oklahoma, from Tulsa to McAlester, for tornado chances, I think there are tornado possibilities under the upper low as well--and strong chances for some amazingly photogenic updrafts and supercells. I'm looking forward to their imagery.
My sights have turned to the weekend in Texas. The GFS has shown chase opportunities for Saturday, Sunday, and even Monday for several runs in a row--and this sounds like exactly what I'm looking for, multiple chase days in favorable terrain, so I am planning as if I'm headed for the lone star state either Thursday or Friday.
Monday, April 04, 2005
Yes, that's right, another system coming up this weekend looks much more westerly than anything we've dealt with so far, and the last three GFS runs in a row have shown some potential for storms in or near the Texas Panhandle region.
Back to the drawing board.
I've decided to sit this one out, yet I am packing my things in case the next Day 2 outlook somehow changes my mind. This is not likely. While I think there's a good chance for supercells, I think they will move very rapidly in the area I most prefer--northeast OK around Tulsa--and will grow linear very rapidly. While this would be a blast if I lived in Texas and only had one afternoon to lose, I don't see this storm system worth my three day investment from Indiana.
Best thing to do, I guess, is grab seven hours of sleep and decide by 10:00 AM. I suppose I could be on the road by around noon and make Tulsa by 10:00 PM. I have not made up my mind.
Sunday, April 03, 2005
ICT's and OUN's most recent discussions here.
According to the ICT discussion, the NAM initialized poorly this morning, which is interesting although it doesn't explain how the last few runs were similar to the 12z's unless they all got off to a rocky start. But then we remember that it wasn't long ago this looked very much like a west-of-35 show. It may not be west of the interstate, but it might be much further west that it looked on the NAM. It is significant that the FO's are adopting the slower, southerly track and chasers should maintain vigilance.
Wednesday in Illinois looks like a weaker version of last Wednesday and is of no interest currently.
Saturday, April 02, 2005
I don't know. But the weirdness of the model makes me think this is looking more like a sucker trap all the time. At the moment I am undecided--you can't take models too literally, and when we step back and see what we have, it's still a potent shortwave sweeping over a moist and unstable airmass. The details become more important as we get closer. I guess by this time tomorrow night, I will have made up my mind.
So we can effectively throw out the timing on Tuesday and say that we have to wait for another batch of runs. This makes all the difference in the world because it determines if the most likely area for severe storms is the chaseable regions west of I-35 or the Ozark Mountains and forests of Missouri, two places I have no interest in visiting no matter how appealing the setup. Other chasers feel differently and are willing to try their hands in a variety of terrain.
We'll know a lot more tonight and tomorrow.
I'm not thrilled about what the models do with the orientation of the trough axis during the afternoon, but at 12z Tuesday it looks vigorous enough to do some damage with about 60 knots of deep layer shear above a fairly aggressive dryline mixing east into around 2000 j/kg MLCAPE. This is a dryline even Neal Rasmussen can love (he thinks what we all call dl's are mostly surface troughs), a genuine, west-wind-behind, gradient-from-hell mixin' dryline. No convergence issues here.
My concerns are the nature of the moist layer (too thin given recent GOM FROPA? gets mixed out by veering low-level winds as trough axis goes positive?) and the shear structure evolution given the projected axis reorientation during the day. If this happens even six hours earlier than expected, the setup is probably ruined. On the other hand, if the trough should find additional jet energy to its south and go more negative tilt than progged, it could be an impressive day.
I have to decide Sunday night, essentially, what I'm doing, then leave Monday morning for Tulsa. I have more work this week than last, and the southern plains is a three-day proposal for me. So this setup has got to look iron-clad on the runs tonight, tomorrow morning, and tomorrow night. We'll see!
Friday, April 01, 2005
The wave I described for next week amplified and dug much further south on last night's GFS, making it a formidable weather-maker possibility on Tuesday in the southern plains. However, because the change was so sudden and drastic, it has to be viewed with great skepticism until it appears consistently on several runs in a row.
The synoptically-evident tornadofest that had appeared at 276 hours yesterday disappeared, too, so I'm glad I saved the output. Tuesday's chances are much closer--120 hours as of last night--so we can take that a little more seriously. A southern Kansas chase would suit me nicely, though I would have to prepare in advance since I'd leave on Monday. Unfortunately the run last night closes the upper low and tracks it through the southern tier of the CONUS, making this a one-day chase event.
I prefer the two-day shows since I have to invest three days to chase in the plains: one for the drive out, one to chase, and a third on the drive home. I don't pull all-nighters on the road anymore; your ability to do that suddenly ends in your late 20's (unless you find the right crack dealer I guess), as hard as it will be for some of my friends to believe. From age 17 to about 28, I used to ONLY drive overnight when going from Texas to New Orleans to see my parents. I would leave around 10:00 PM and arrive about 7:00 AM the next morning. It was fun. I couldn't do that now if I had to. I wouldn't want to, that's for sure--it's a guaranteed way, at age 35, to feel like hell for about three days.