2018 severe wx/chase season discussion

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

  1. Andy Wehrle

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    They note 2006 as a "notably active exception" but that is almost universally reviled as one of the worst overall chase seasons since the turn of the millennium. Most of that activity was in the jungles, and it shut down after April 15. May was dominated by a cool eastern trough.

    Based solely on my arm chair knowledge of meteorology/climatology, ENSO is overrated as a predictor of US tornado activity and chase season quality. PDO/PNA seem to play a far bigger role, although the details as to how and why are beyond the scope of my knowledge.
     
  2. Andy Berrington

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    Save 2013, the years listed in that analog composite are basically a smorgasbord of generally terrible chase seasons, especially in May. Also, the stubborn +PDO has been on yet another rising trend over the last three months.
     
  3. Brandon Centeno

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    B11DBFEA-D376-4DC1-B957-8C579344B256.jpeg

    Here’s hoping the upcoming (big) decline in AAM will yield quality events. Quite the signal there for a propensity for western US troughing.
     
  4. Jeff Duda

    Jeff Duda Resident meteorological expert
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    Moderator note

    Since this thread is evolving into the typical "state of the season: YYYY edition" type thread, I have gone ahead and renamed it thusly. Keep the good discussion going!
     
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  5. Brandon Centeno

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    Interesting, if not impressive agreement from a week out on western US troughing by the GFS, ECMWF, and CMC.

    500h_anom.conus.png CMC.png GFS.png

    Obviously each of the three have their differences, but there should be relatively high confidence in some degree of severe threat evolving over some portion of the plains, especially due to the increasing confidence low-level moisture will be in abundance. Looks like an eastern Great Plains event could be on the way.

    From an analogue sense, there seems to be a signal of enhanced predictability, given spatial probabilities associated with fcst pattern:
    LR.png
    Lines up nicely with where the threat area likely will be should the major models hold. Using a threshold of a minimum of 1 tornado report:

    PRTORNC01_gefsF168.png


    Certainly, this event bears watching. Even though the upcoming amplification of the east coast pattern blasts the gulf with a cold front, the extremely warm gulf SSTs, and more importantly, a favorable large-scale pattern evolution looks to allow an abundance of moisture into the plains. When you get favorable moisture return in the early season paired with an impressive mid-upper level system, big things can happen.
     
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    #30 Brandon Centeno, Mar 11, 2018
    Last edited: Mar 11, 2018
  6. Andy Wehrle

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    It's obviously way out in clown land, but there's been a signal for several GFS runs now of another significant system crossing the central CONUS after the first. It's interesting how the 06Z run goes from no CAPE over NW TX/SW OK at 18Z Thursday the 22nd, to almost 2000 j/kg and a PDS TOR hazard type on the soundings valid for 06Z (1AM) Friday the 23rd! That would be a very scary situation if the soundings looked like that at verification hour! By 18Z Friday it bombs the low out to 969 MB over central NE!
     
  7. Jeff Duda

    Jeff Duda Resident meteorological expert
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    There are some signs of an event showing up on the CFS dashboard (reminder URL: http://www.spc.noaa.gov/exper/CFS_Dashboard/) for the 17-18 March period, but only a handful of recent runs are showing it. Also, given the shape of the SCP and precip fields, it's hard to tell whether the model is catching a dryline forced event or more general convection associated with a completely different forecast trough. At that forecast range (day 10-18) there is absolutely no guarantee the model is even forecasting the same synoptic scale evolution.
     
  8. Jonathan Beeson

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    This is the first real "traditional" synoptic look of the spring for a severe weather setup for the plains and points eastward, which gives me a little bit more confidence in the models than this past weekend's NW flow mess.

    Also, of interest to me is that both the GFS and the Euro have a weaker primer system traversing the area late this week and into the weekend ahead of the stronger system next week. That may help moisture return get into place considering March usually isn't the most favorable month climatology wise for robust moisture return.
     
  9. Quincy Vagell

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    Is it just me, or has that dashboard not updated since March 6th? I realize there are many other places to access CFS data, but I'm just making sure.

    To chime in on the "state" of the severe weather season, I'm really not very impressed with progs for this weekend into early next week. The models have been inconsistent and are feeling around for the evolution of the pattern.

    Taken literally, the 12z Euro (largely supported by the EPS) shows substantial troughing across eastern North America, which limits moisture return across the central U.S. Combine that with a fast flow, featuring several systems, and there isn't much reason to believe there can be substantial moisture transport, i.e. dew-points over 60F, overlapping with favorable CAPE/shear profiles, much farther north than the Arklatex vicinity. This of course, is unless the evolution drastically changes. Furthermore, the data suggests that troughing over the eastern Pacific is going to throw yet another wrench in this pattern.

    It looks to me that several surface lows will quite possibly, if not probably, eject from the Rockies into the Plains over the next 7-10 days, but it does not appear that any of these systems will emerge as a substantive low, capable of producing more than isolated/spotty severe.

    I'm not too worried about it, since it's still early in the season. I'd rather see this sort of junky setup in March than April, given the overall lack of moisture, model consistency and perhaps most importantly, lack of ridging across the eastern third of the continental U.S.

    Sure, it's possible that one or two of these systems may improve somewhat as time moves on, but I wouldn't start rearranging plans or scheduling any sudden chasecations just yet.
     
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    #34 Quincy Vagell, Mar 12, 2018
    Last edited: Mar 12, 2018
  10. Jeff Duda

    Jeff Duda Resident meteorological expert
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    Good catch! I did not see that at first. That's unfortunate, as that site offered IMO the best graphical display of CFS uncertainty specifically for severe threats. It is hard to find good CFS data elsewhere. I know http://cfs.hopwrf.info/ still plots CFS graphics, but only starting at week 3 and beyond. Otherwise, COD still plots deterministic CFS runs, but they don't make any TLE products, just their dProg/dt display option.

    As to what Brandon and Quincy have discussed, I have seen a persistent trend for negative 500 mb height anomalies dominating western North America through the 6-14 day range, which implies a lot of western US troughing. And this is not just one wave, either, but rather a succession of troughs coming out across the southwest and west central US. If it was late April or May I would be very excited about the prospect of an extended period of severe weather. But the last few troughs that have affected the central/eastern US have done their part to mostly clean out the Gulf of good moisture, and moisture return is not going to be as rapid at this time of year as it will be two months from now, so that's one of many ingredients that will probably not be in place to make any of these troughs particularly threatening for good severe weather.
     
  11. Brandon Centeno

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    It is rather disappointing to see the recent trends in model guidance. To me, the killer isn’t quite the eastern trough. While having a stouter ridge in place would certainly help, sustained vort maxima traversing the plains actually seems to be distorting the surface pattern and really veering the flow such that moisture return is being significantly impeded compared to earlier runs.

    I’ve seen a lot of “too bad this pattern is happening now and not later.” Friendly reminder that patterns are not used up! There’s no magical well the atmosphere goes digging through until it runs dry in June. For all we know, April and May could be dominated by a central US ridge like last season. It could also be dominated by western troughing. Sure seems like we are headed for an active base state similar to one of the more active seasons in recent history. GWO forecasts show no sign of slowing down, granted there is a bit of noise at the week 3 range leading to uncertainty. Inevitably a quiet stretch will come by, but it could simply be an active year for us in the plains. This is suggested by research focusing on declining Nina years. We will see what that holds; but I believe there is reason to be quite optimistic about plains chasing this year.
     
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  12. Tim Paitz

    Tim Paitz EF2

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    I'm being St. Louis-centric with this, but what about St. Louis? :)

    I mean, March is pretty much shot, Intellicast is showing chilly weather for some time, and there hasn't been much severe weather in the spring here for the past few years. We already had the best severe weather at this point last year.


    I've been thinking about buying a couple dashcams for my car in the miraculous event there is chaseable severe weather around here.
     
  13. DNewman

    DNewman EF1

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    Now that we are in mid March. I'd like to see and hear the latest thoughts regarding the severe weather season. Especially seeing drastically increased rainfall across areas near and east of I-35 during mid to late February, which significantly put a dent in ongoing drought conditions or eliminated them completely. I have been monitoring low level features and upper level patterns over the last several weeks since late February. And I've noticed strikingly similar setups to 2011 with the dryline surging much farther east past the I-35 corridor in the last couple of weeks here in Texas. When the dryline doesn't mix out west of I-35 and continues into deep east Texas during the spring , this more often times than not means significant drought and or very dry soil, vegetation conditions across western areas of the state of Texas. Which is why we saw repeated events either east of Texas from 2011-2014 or in a handful of cases from near I-35 and points east from March through April, with reduced events in May. Being in Texas all my life and studying state weather anomolies and climate patterns (being no expert however). I'd be willing to put money on a more active Spring severe weather season due to a lingering very weak La Nina affect that will continue into the upcoming months, before turning more neutral by June. Areas along and east of I-35 have a higher chance at seeing above average severe weather this season from Texas to Kansas primarily, with the farther east you are, the better your chances of seeing more tornadoes from my experience. The entirety of the panhandles of Ok/Tx into western Kansas and into west Texas and areas nearby have yet to see any meaningful precip, and this will not get any better this spring.
     
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  14. Warren Faidley

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    I have no reason to think the spring SVR regions for 2018 will be any different than recent drought years. The western regions of Texas, Oklahoma and Kansas are still suffering from drought conditions with almost weekly extreme fire risks. Soil moisture content is something I always consider as the season progresses. The current soil moisture map (link below) is hauntingly similar to where the true DL has been setting up on average since the drought began, with the exception of course for late season RH which generally remains undisturbed. It would be interesting to overlay severe weather events on these maps over a course of months / years. (Map source: https://www.drought.gov/drought/data-maps-tools/soil-moisture) curr.w.full.daily.gif
     
  15. Jeff House

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    Believe it will be difficult to get a true trough west ridge east pattern while the atmosphere works through the sudden stratospheric warming SSW hangover and continued blocking. Early in the season one really needs a ridge back East to help moisture return. Rest of March I predict BN activity but that does not mean no activity.

    If the La Nina breaks down correctly, anomalies warming in 1-2 before 3-4, the TNI could set up bullish. Subsurface right now is not pointing that way, but much can change before the April predictability barrier. Either way I expect closer to normal activity in April as the SSW hangover ends.
     
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  16. Michael Snyder

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    It's going to be like most other years, good for some, junk for others, periods of inactivity, periods of higher activity.

     
  17. Tim Paitz

    Tim Paitz EF2

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    This cold, rainy November-like weather needs to GTF outta here. Now.
     
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  18. Quincy Vagell

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    March will likely end as another below average month in terms of tornadoes across the U.S.

    There is at least some potential for spotty severe from Sunday through Tuesday, but none of those days particularly stands out, despite having a slow-moving trough moving from the Southwest into the southern Rockies. It's a case of being early in the season and nearly constant troughing over the eastern U.S.

    Sunday's threat is quite conditional, but there does appear to be a narrow corridor from North Texas into the Red River Valley region that could support an isolated supercell threat. Forcing, both large scale and mesoscale, appears limited, but model forecast soundings have trended toward better boundary layer heating than previous days. This may be enough to erode surface-based convective inhibition.

    Monday could be a bigger day, if it was not for messy looking wind profiles. There is a veer-back-veer signature in almost all forecast soundings, and hodographs are not impressive at all, especially in the 0-3km layer. Mesoscale details could augment some of the kinematic issues, but I doubt this will be a significant or widespread severe day.

    Tuesday's threat pushes south across Texas and the lower Mississippi Valley region. Wind profiles become worse, largely unidirectional as a sagging frontal boundary becomes increasingly parallel to the deep layer shear vectors. A squall line with thunder and locally excessive rainfall will likely evolve.

    There is not much hope for substantial rainfall over the High Plains in the days ahead, but areas from I-35 and points east will see several opportunities for heavy rain over the next 3-5 days.

    Once the trough moves east, the pattern looks relatively quiet through the end of March, with a generally WNW flow aloft and no notable areas of low pressure across the Plains. This will probably result in a continued threat of fire weather from the southern Rockies into the High Plains.
     
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  19. TJ Schulte

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    I’ll tell you what guys this has been one long winter. December was brutally cold, and here we are in late March with still the same pattern. Even today in Toledo, it’s a high of 38 with pure sunshine.

    I will say the jet has been pretty active (just look at the amount of nor easters) so when the pattern shifts I’d look for it to be active in the severe season. Last year we saw an incredibly active early severe season just shut down by the time May rolled around, a reverse of that would be nice and I’d expect it honestly
     
  20. Ethan Lang

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    I have had only one chaseable setup in my area and it was on the one night of that week where I was busy and unable to chase
     
  21. Quincy Vagell

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    The next two weeks look awfully dull, especially once we get past the Texas/Gulf Coast threats of the next couple of days.

    The CFS, GEFS and EPS are all in agreement with minimal Plains instability and the dreaded eastern U.S. troughiness. As we move deeper into April, I won't speculate too much as mesoscale details can result in localized threats (as moisture return becomes climatologically more widespread), but even April weeks 2-3 may very well end up with below average severe activity.
     
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  22. Jeff Duda

    Jeff Duda Resident meteorological expert
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    This is pretty consistent with what the CFS dashboard and Dr. Gensini's ERTAF are both saying. Helpful links to those who may not be aware of these products or their recent moves.
     
  23. Dan Robinson

    Dan Robinson WxLibrary Editor
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    2004 had a couple of minor events in March and a pretty dull April in the Plains. I'm curious to see the longwave pattern looked like for that April to see if there are any similarities with this one. 2004 then went historic (in terms of chaser successes) after May 12. Before May 12 it was pretty dismal, but it really turned on a dime.
     
    #48 Dan Robinson, Mar 27, 2018
    Last edited: Mar 28, 2018
  24. Andy Wehrle

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    There were a couple of 15 hatched MDT days in OK mid-late April 2004 that largely underperformed the implications of an outlook like that. Most activity ended up being HP/undercut/cold RFD. A lot of potential setups in April 2013 turned out in similar fashion. As I recall that was another winter that didn't want to let go.
     
  25. Quincy Vagell

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    I pulled some of the upper air analyses from 2004 and there are some similarities, but differences as well. I'll share some of them below, but nothing is really conclusive in showing a strong pattern match.

    Looking at March, 2004 and 2018 are quite different.

    March of 2004 saw positive 500mb height anomalies across the continental U.S. with sharply negative height anomalies displaced to the Polar region, north of Canada. Surface temperatures were at or above average for just about all of the CONUS, but well above average over the central and western U.S. The month also saw an unseasonably far north shift in tornado activity, with clusters of tornadoes from North Texas into northwestern Oklahoma and central Kansas, likely due in part to the northward displacement (compared to climo) of the jet stream and resultant above average temperatures over the Plains.
    500_mb_04_vs_18.png
    On the other hand, 2018 has featured nearly constant troughing across the eastern U.S. with some troughing over the West Coast. Surface temperature anomalies show below average temperatures common across the northern and eastern tier of states, with above average temperatures over the southern Plains/southern Rockies.
    sfc_temp_04_vs_18.png

    Looking ahead, let's start with some of the similarities.

    The early April progs for 2018 are similar to what was observed over April of 2004. If the forecast holds, troughing (negative height anomalies) will prevail over central/eastern Canada with ridging in the northeastern Pacific. Tornado activity for early April 2004 was unusually low, with just 29 tornadoes occurring from April 1-15.
    apr_04_observed_png.png
    For differences, the longer range data, namely the European weeklies, suggests large scale troughing prevails across much of Canada, with a tendency toward positive height anomalies (ridging) from the northern Pacific into the Bering Sea. In 2004, ridging was evident over the northeastern Pacific/western Canada, but troughing occurred southwest of Alaska. This pattern ultimately shifted eastward, allowing for a series of upper level troughs to dive across the western U.S., supporting increased tornado activity (well above average) in May across the Plains and Midwest.

    An interesting note is that early spring 1997 is a common theme in the CPC day 6-10 analogs, accounting for 3/10 of the analogs. Years don't usually show up more than once or twice unless there is a strong correlation. Note that the northeastern U.S. saw a historic early spring snow storm from March 31-April 1, which fits the pattern of this year, as March has been much snowier than average in that part of the country.
    610analog_mar_28_2018.gif

    Final thoughts:
    I've dabbled a bit in analogs and long-range tornado prediction over the past few years and it's been tough. While there have been some successes, there have also been challenges as well. Since it only takes one or two big events to skew an entire tornado season, an otherwise quiet tornado season can be offset by a tornado outbreak sequence or even just a single historic event. Mesoscale details are important when considering tornadogenesis. A favorable looking pattern can go on to be a dud (April 2004 and 2013 were mentioned in this thread), while a relatively zonal flow can feature localized tornado outbreaks, if mesoscale features like a warm front or outflow boundary line up just right. May 18th, 2017 was an example of a tornado-driven high risk struggling to produce many photogenic tornadoes in the risk area, west of I-35, while most of the tornadoes of the event happened after dark in eastern Oklahoma and the Ozarks, displaced far from the high risk area.

    The bottom line is that predicting tornado activity inside of two weeks is considerably easier than the period of 3-4 weeks out and beyond. You can't predict a mesoscale "accident" a month in advance, let alone inside of 24 hours, sometimes...

    It's safe to say that April will most likely start with well below average tornado activity, but what happens beyond that is anybody's guess. I may dive a bit deeper into analyzing some analogs and such, but I'm not sure how worth it that is. Many of us are getting anxious for the upcoming peak tornado season, when it finally arrives. I'm somewhat more inclined to just leisurely look at weather maps and wait for May to surprise us with whatever nature has up its sleeve.
     
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    #50 Quincy Vagell, Mar 28, 2018
    Last edited: Mar 28, 2018

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