2018 severe wx/chase season discussion

Discussion in 'Advanced weather & chasing' started by Warren Faidley, Feb 6, 2018.

  1. Jeff House

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    Hi @Richard Mark Stephens, I second what @Royce Sheibal says previous page. Kind of depends on your risk (of failure) tolerance. Gosh, I sound like a mutual fund adviser!

    I believe 3-5 chasable set-ups will take place next week, probably not in a row. Could be in pairs or 3 and 1. Yeah targets might be pretty spread out even from one day to the next.

    What is considered success? If one decent tornado, I think you can do it. If looking for two good tornado days, assuming a .333 batting average, it could be tough. Who knows, just one multi-cyclical meso-scale accident can make a year.

    You know what's most frustrating? Not having a total solar eclipse to fall back on in August!
     
  2. Quincy Vagell

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    In times like these, I like to watch the patterns day by day without getting to ahead of myself. "Day before the day" is a good motto, as some of the days in the past that were not hyped up, ended up performing. Predictability with respect to mesoscale details is very difficult in a pattern like this. Yes, Friday looks to have some "enhanced" potential, but for now, I'm focused on the complexities of the next two days. The synoptic pattern does not look great by any stretch of the imagination, but severe weather should occur both days and I'd think there will be some photogenic storms, somewhere...

    Tomorrow (Wednesday) features modestly rising heights and lackluster deep layer wind fields, however, the recent trends suggest that the southern High Plains has some chase potential. Combine marginally favorable upper level winds with the possibility for leftover outflow boundaries and the West Texas vicinity looks like the area to go for. As recently as this afternoon, my initial plan was to target the central High Plains tomorrow, but I'll explain why that's becoming less and less likely, aside from the fact that any robust convection, period, appears highly conditional there.

    Thursday should feature increasing mid and upper level flow as Plains ridging eases a bit, in response to the slow approach of a shortwave trough. The interesting thing with Thursday is that there should be a very broad threat area, expanding from the southern Plains, all the way up to North Dakota. Going back to an earlier thought, I really like the looks of North Dakota (possibly northern South Dakota) on Thursday, but with Wednesday's target trending south, the Dakotas play for the day after tomorrow seems unrealistic, at least for me and most people on chasecations. If you're up north and can't chase Wednesday, don't overlook Thursday, locally.

    This is yet another example of not getting too far ahead of the forecast. With that said, the threat area should become more focused and clear for Friday as the large scale pattern is more indicative of what you'd like to see for severe weather in the Plains in May.

    Remain cautiously optimistic. We may have some ridging over the Plains, but we don't have a death grip from the ridge just yet. Expect almost daily chase"able" targets through at least Friday and days beyond that don't look like shutouts either.
     
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  3. Andy Wehrle

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    Am I seeing things or did 06Z GFS just significantly up the ante for Saturday over NE KS/SE NE?

    Still on the fence about Friday due to distance (would basically have to leave immediately after work Thursday afternoon and stay overnight somewhere en route) and now moisture concerns.
     
  4. JamesCaruso

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    I really don’t see the appeal of the northwestern portion of SPC’s outlooked area for Friday. I don’t like the northeasterly surface winds in northeastern CO, and even the mid levels appear to back somewhat. The Denver AFD also mentions easterly 500/700 flow. I am more interested in southwestern KS, maybe east of DDC, where surface winds are backed, the LLJ looks good, and there should be sufficient moisture. Outflow boundaries from Thursday night may help or hurt this particular area, but will definitely complicate the forecast. Looking at flying to ICT on Friday morning; it’s somewhat risky to make it in time, but a Thursday afternoon flight from Philadelphia is a little challenging at this point.

    Saturday I think is potentially a triple point play in northwestern OK, but I’m not thrilled with messing around with the cold front.

    Sunday I am thinking southeastern TX panhandle. Decent moisture makes it into the region. Flow is weak (25 knots) but magic can happen there. The AMA AFD says Sunday is its forecast area’s “next ‘interesting’ day” for severe weather.

    Monday I am less comfortable with, flow remains quite weak, would hope for some Colorado magic but moisture will be limited, even for that region where we can do more with less.

    Looks like a potential midweek play up in the Dakotas but I am not looking too far out in detail at this point.

    Still wrestling with whether to make the trip only because of my daughters’ being in a play on Sunday but they always knew I would likely be out chasing and I think if anything it goes downhill after these next few days so might as well get out there, worried this could be it unless the next week beginning with Memorial Day Weekend turns around.
     
  5. Paul Knightley

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    Ensemble output through next week throws up a few chances early-mid week, with hints of a southern stream closed low/trough moving in from the SW, but trends have taken this a little west - even so, some upslope fun could be had for parts of the west central Plains.

    Later in the week there are indications of a trough moving into the PAC NW...but then considerable differences in its evolution thereafter. ECMWF ensembles have trended towards bringing it further inland 25/26th May onwards - but with the blocked pattern of late, confidence is below average for output in the medium range.
     
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  6. Jeff House

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    Paul covers my mid-long range thoughts well, so I will switch to short-term.

    Maybe not worth starting a Target Area thread for just one Saturday thought, but I want to note caution for the CF/DL intersection. Normally a second target behind, east of the surface low, but Saturday ECMWF has terribly low dewpoints near the CF/DL. One might be forced to settle for east of the surface low, and hoping no MCS wash-out. Saturday is four days out; so, much can change either direction. GFS votes Bennington 4 (kind of).

    After 12Z data I may opine on Thursday and Friday, perhaps in Target Area if threads are already going.

    Finally, @Tony Laubach I am glad nobody was hurt in your May 14th chase. Other driver on cell phone? Cannot really reply in Target Area, so I do so here. Everybody, I think Tony sets a great example of focusing on the positive. Chase vehicle was totaled, other driver's fault. However Tony celebrates a successful tornado intercept and living in Kansas. Yeah, I miss that last part.
     
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  7. Andy Wehrle

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    Agreed, great intercept for Tony of a surprise photogenic tornado. Bad way to end the day but glad no one was hurt!
     
  8. Quincy Vagell

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    The GFS and Euro diverge quite a bit.

    In general, I'm not particularly fond of sweeping cold fronts. The Euro and NAM (take the latter with a grain of salt at this range) show increasingly unidirectional flow in the mid and upper levels by Saturday afternoon.

    While the GFS does look more favorable with much better 850mb winds (S to SE), it is slower/farther west than the Euro. The GFS has the 850mb low over northwestern KS at 00z Sun, while the Euro is up near Omaha.

    My guess is that the setup needs to slow down, or it needs a more pronounced dryline over eastern KS to help with shear. I can recall a couple of eastern KS dryline threats this season that both more or less fumbled. It can be done, but the needle would need to be threaded just right.

    I may also be slightly biased since I can't chase on Saturday, but objectively, it's far from a slam dunk, so I do agree with SPC's "predictability too low" for day 4.
     
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  9. chrisbray

    chrisbray EF4

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    84 Hour nam (taken with grain of salt) in agreement with 6z GFS in regards to potential in IA/MO/IL warm sector Saturday.
     
  10. Jeff House

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    12Z NAM seems to vote ECMWF over GFS. Unfortunately it may be right. 12Z soundings have upstream air over OK/TX scoured our harshly at 925/850 mb. Tenn Valley low did a number on the moisture. NAM struggles to get Td65 into the Kansas target zone Friday. I prefer Td68+ so a caution flag. Sounding forecasts have that moisture recovering JIT, but then mixing out again at lowest levels. Radar simulation Friday looks like trash because the model is trying to gust out the storms on insufficient dewpoints. No inflow signatures on 850/925 mb or lowest 30mb or 80 meters. All of those show gust out signatures. Could be model cancer at hour 60 but it is very discouraging.

    Well @Quincy Vagell you are (likely) not missing anything Saturday. Thursday I see the Denver Cyclone play. Friday could be Raton Mesa magic but very subject to overnight and morning convection. When the pattern is awful, I look for physical geography help. Even nicer with outflow juxtaposition. Good luck to all!
     
  11. Dan Robinson

    Dan Robinson WxLibrary Editor
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    That's the problem with these "ripples in the flow" setups without a robust warm sector. They have very little tolerance for things going wrong and no spatial coverage for the targets to shift before things are hopelessly out of alignment. Friday's setup seems to be hanging on a thread with no room for anything at the surface or aloft to shift even 50 miles in any direction. Saturday's NAM has the better overlap of decent flow and moisture, but surface flow is weak (and in Iowa of course).
     
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    #236 Dan Robinson, May 16, 2018
    Last edited: May 16, 2018
  12. Tony Laubach

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    Thank you... no, per the driver, she was a little freaked out about the tornado warning and was trying to get home from work. I don't think she was on a cell phone. Unfortunately I didn't get that great a look at her prior to impact ;)
     
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  13. Quincy Vagell

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    The 12z Euro shows a prolonged period with relatively unfavorable (marginally favorable at best) upper level flow from days 4-10, pretty much all of next week. Winds struggle to reach 30kts at 500mb, even for the balance of this week. That coupled with the CFS "looking blue" next week is a sign that any widespread or significant severe weather will be fairly unlikely, barring a significant synoptic change in the model progs.

    As always, localized severe events remain possible, as well as mesoscale "accidents," but aside from that, the outlook is not encouraging.
     
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  14. JamesCaruso

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    Now I’m really depressed. This morning I made the decision I was a “go” for Friday morning and earlier today booked a flight to Wichita. I wasn’t expecting much and was just in the “when it’s May, you chase,” for better or for worse mindset. But now you guys have me second-guessing that decision, with the above posts sounding bleaker than ever. In a normal year I wouldn’t care, but now I am missing my daughters’ play on Sunday. The last thing I want to do is end up missing that for absolutely no reason, jerking around out there under a blue sky, unable to even claim to actually be chasing, and who knows, maybe even coming home a few days later if nothing is on the horizon. What a ridiculous scenario that would be...

    I can always cancel the flight, I was just using mileage anyway, I guess at this point I will make another go/no-go decision at this time tomorrow night.
     
  15. Brandon Centeno

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    0E4CC3EC-9F4B-4120-BE44-D72998BF1FBB.png

    E91640D2-C8CD-4B73-9DB3-40F55BBD3EC6.png Regarding near term..

    Moisture is not terribly promising for any of the upcoming three days. NAM is, predictably, pulling back substantially on its outlier 84 hour forecast everyone freaked out about.

    A big reason I am having second thoughts on my upcoming Friday chase is the current state of the gulf. Moisture across the coastal plains of Texas, LA, etc are not tropical at all. In fact it’s modified continental air rather than any sort of maritime airmass. The LCH sfc Td and mean mixing ratio are both at or below the 25th % for moving average.... not exactly what you want to see this time of year 48 hours before an event.

    Moisture should improve by Saturday, but not nearly to the degree the NAM is showing. Yes there will be storms, but whether they are supercellular and/or tornadic is a much different story.
     

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  16. Jeff Duda

    Jeff Duda Resident meteorological expert
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    The moisture problem stems from the fact that we haven't really had a trough take a southerly-enough track since the beginning of the month to induce deep, strong onshore flow from the Gulf, and thus the metaphorical "firehose" of moisture from the Gulf has been more like a trickle or has been shut off. The decent moisture that is in place currently is the result of 10+ days of no cold fronts to clear out the moisture + ET + what little trickle of moisture is actually coming in off the Gulf.

    As long as we continue to be locked into this split-flow pattern where the main polar jet is along or north of the Canadian border and all we get are these measly cutoffs oozing into the Rockies before stalling and filling, there will be insufficient widespread flow for supercells and also generally no synoptic scale moisture return off the Gulf. Can't say return flow off the western Atlantic is out of the question, but the trajectories needed for such moisture to reach the Plains are less than probable. It also doesn't help that the subtropical jet is a bit far south and for some reason is failing to generate the troughs we would need to see good Plains setups.

    I think I mentioned this before, but this kind of seasonal evolution is why I hate seeing really active troughing patterns in March-early April. I know this isn't entirely scientific to say, but it does seem like that type of pattern (frequent high-amplitude troughs crossing the CONUS) exhausts itself after a few weeks or up to a month or two, and then it seems like it has to reload. So when that pattern sets up too early, you get this death ridge/split flow/zonal flow lameass crap during the climatological peak of the season. What I like to see is the active troughing pattern set up starting mid-late April so that synoptic-scale cyclogenesis episodes coincide with the stronger diabatic heating and better moisture return of mid-late spring rather than early spring when CP air masses still pervade the eastern 2/3rds of the US and moisture is always questionable. In the former cases you're much more likely to have the ingredients in place for a prolonged period of more significant severe events, at least a few of which are bound to promote satisfying chase setups and/or tornado outbreaks.
     
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  17. JamesCaruso

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    Jeff, this is an interesting observation. You gave the caveat that it “isn’t entirely scientific,” but as a non-meteorologist that is limited to anecdotal observations and pattern recognition, I would similarly always get uneasy about what would be “left” during peak chasing season if there had already been a lot of early activity.

    This year, however, there hasn’t been much activity, so I am surprised at how poorly things are turning out. I wasn’t really following Plains weather much back in March/April, except to be generally aware from this forum that things were off to a slow start. So I am surprised to see your observation that it was actually *too active*, *too early*. In retrospect, having been focused more on the unusual frequency/severity of winter storms for that time of year here in Philadelphia, I guess there were a relatively high number of troughs crossing the country back then (at least in March; I don’t remember much about April, but if anything wasn’t there a persistent trough in the east and ridging in the west?)

    So then how does all this (frequent early season troughs) reconcile with such a slow severe weather season in the Plains? Why weren’t those troughs producing at the time? Was it the path they took, i.e. not digging into the Plains? You mention the lack of moisture at that time of year, but wouldn’t the troughs, if present, facilitate moisture return at any time of year? I guess you are saying it’s not that a favorable pattern per se has exhausted itself, it’s more just the absolute number of troughs that we’ve pretty much “used up” so to speak, is that a fair characterization? Still, hasn’t the atmosphere had sufficient time to “reload” by now? Are you thinking that it “reloads” by June or are we pretty much done in your estimation?

    Thanks for helping me better understand this and put some context around my disappointment.
     
    #242 JamesCaruso, May 17, 2018
    Last edited: May 17, 2018
  18. Paul Knightley

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    This season has been dominated by a blocky pattern in the jet, largely as a hangover from the major sudden stratospheric warming event we had in late winter. This really disrupted the polar vortex and since then we've seen rather anemic flow around the N Hem. Tropical forcing seems to be fairly non-existent, and no doubt sea temps in the N Pacific will have had some effect on the way the jet behaves. Interestingly, 2006 has come up numerous times this year so far as an analogue (although 2013 is one too) based on various teleconnection indices, and 2006 was a poor year, overall, for chasing.
     
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  19. Andy Wehrle

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    Strange thing is though, I remember May 2006 being very cool with hardly any storms, just stratiform showers when we got rain. This May we've had plenty of summerlike days and no shortage of thunderstorms (in fact already the 4th wettest May on record for Madison), just nothing to get them to severe levels on an organized scale.
     
  20. Royce Sheibal

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    @Jeff Duda I think you're being more scientific than you realize. We had a very strongly swinging MJO from Feb-April, which tends to encourage your massive troughs. Now that the MJO has finally settled down in magnitude (as would be expected after a several month up period) we're stuck in the MJO doldrums, which are not great for troughs. Some amplification would be nice, sadly it doesn't look too promising right now.

    [​IMG] [​IMG]
     
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  21. Brett Nickeson

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    The folks above have more scientific explanations of why this occurred, but in general the answer is that it was still basically winter when the jet was active. It's hard to get moisture and adequate instability when you're at 45 degrees for a high and it's snowing once a week up through early April. We went straight from a winter pattern and 25 degrees below normal to a late June pattern and 15 degrees above normal within about a two week period.

    Just a miserable, miserable year.
     
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  22. Eric Bucsela

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    Thanks for your comments Dan but I’m still not clear why Friday looks so marginal, esp in SW KS. To my non-professional eye, both NAM and GFS show decent wind fields, CAPE approaching 3000 and a breakable cap. At least one NAM run has a cell pop in that area by 0-3z. DPs are already in mid- to upper 50s and a little advection could help that. DDC is somewhat optimistic but SPC is obviously not too jazzed. Guess I still have a lot to learn!
     
  23. Jeff Duda

    Jeff Duda Resident meteorological expert
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    As far as "active" goes, I was referring to the frequent troughing, not to severe weather report numbers.

    Troughing does not guarantee sufficient moisture return in the early season. If a major cold front swept out the entire CONUS east of the Rockies and the Gulf itself of moisture, all the 50 kt surface southerlies off the Gulf wouldn't do a damn thing to restore moisture over land. With less direct heating in the early season, it takes longer for evaporation of surface water off the gulf to "recharge" the atmosphere with moisture also. Furthermore, while this is less common of a failure mechanism, if you're coming off a major drought (such as was the case in the south-central/southwest US this past winter) in a source region for good lapse rates, that can promote early EMLs and capping. March sun isn't all that strong just yet, so diurnal destabilization is also not guaranteed to break early season caps if they're strong enough.

    So there can remain multiple failure modes in the presence of even a strong trough in the early season.

    Regarding your last set of questions - as I mentioned, my interpretation was not entirely scientific, meaning I can't identify a single set of physical processes that mystically govern the total number of troughs that will cross any given longitude in a year, although I do suspect there are underlying larger-scale physics processes that may indeed explain this phenomenon. [ADD: As Royce mentioned, I should probably be looking at MJO indices. Unfortunately my knowledge of larger-scale processes is pretty lacking, as I never studied those in school. Seems like others in this thread have a better handle on it, though.] So I would be hesitant to use the phrase "used up our number of troughs for the season", although that is kind of what I'm hinting at. I have no idea how much time it would take for a more active pattern to reappear, so I cannot say with any certainty whether we may be done for the season as far as large-scale troughs go. Typically June is ruled by mesoscale setups anyway, as moisture and heating are generally always there; you generally only need some sheared flow somewhere to get a big event, and you don't necessarily need a big trough to get sheared flow.
     
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    #248 Jeff Duda, May 17, 2018
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  24. Jeff House

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    Friday trouble is dewpoints/LCLs. Moisture will try to recover but 850/925 mb was scoured by the Tenn. Valley trough. Forecast soundings revert to inverted V by late afternoon Friday lowest levels - allows evaporative cooling gust out. Even at the ground South Texas dews are below 70 - awful. ARW version of the WRF really does not get target area dews to even 60 deg. Touches it and mixes out. NAM version of the WRF, usually pretty bullish, barely touches 65 before mixing out. Both CAMs low level wind fields and reflectivity look like gust outs early. Might get a quick landspout, but I can't see a path to a good multi-cycle show.

    Saturday CAMs don't look a whole lot better but I think dews will be higher. Goal is to avoid a mess of clusters. CAMs might improve. Fundamentals are not bad. Models show a slightly veered LLJ, but not a problem considering westerlies farther up. Plenty of outflow boundaries. Maybe just too much convection too early?

    Here is my take on this weekend vs a Major or mid-major family event (FE). It is understood that minor FEs are blown off for chasing. Mid-major FEs might get skipped for an excellent chase set-up. I would not skip a Major FE for any chase set-up. @JamesCaruso I really wanted to PM but ST setting(s) will not permit. If the play is a mid-major FE I see a 50/50 choice. If the play is a Major FE, I would personally not chase. However each individual is different, with unique risk tolerances and relationships. Stormtrack is a like Planet Fitness, a judgement free zone. I might chase 50/50 a great/excellent set-up (this is not) if the play/sports game was regular season (mid-major FE). A first ever play, or sports post-season feels more like a Major FE. Lurkers, I cannot stress enough these are personal choices.

    The following may be as scientifically awful as predicting EF levels, but I want to quantify this weekend. Friday and Saturday both probably have about a 40% chance of producing more than a landspout. Add other factors like cell selection, roads, whatever, and probably go 20% chance of success each day - likely generous. 80% chance of failure, but 64% of failing both days, so 36% chance of intercepting at least one day. However the chance of something memorable is probably 10% or less. I prefer 33% or better odds.

    And that 33% is with nothing on the family calendar. This weekend I have nothing, but I am still not chasing. Maybe I'm too pessimistic. We were packing our bags, and punted the plan around 00Z yesterday. I may miss the next Rozel, but I doubt it. Those chasing, I do wish you good luck!
     
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    #249 Jeff House, May 17, 2018
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  25. Dan Robinson

    Dan Robinson WxLibrary Editor
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    In a "good" season, you have abundant moisture and broad areas of upper level flow that overlap in large areas, maximizing the potential for healthy supercells and for one or more of them to benefit from a small-scale feature like a dryline bulge, warm front or outflow boundary. In seasons like this, deep moisture and upper support are occurring in only very small areas (if at all), meaning the chances for them to overlap at the right time are very low, much less be coincident with an OFB or some other mesoscale feature that could enhance tornado potential. It's just harder in our current setup to get everything you need to line up correctly because the basic ingredients are in short supply.
     
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