Upcoming Chase Season: 2017 Edition

Discussion in 'Advanced weather & chasing' started by James Gustina, Jan 14, 2017.

  1. James Gustina

    James Gustina Member

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    Coming back with one of these threads a bit late this year. Seems like a nice way to pass the time during the first few lean months of the year when there's not much else to talk about other than rampant speculation based on oscillations and climate progs.

    Just to kick things off, the good news is that the worst area of drought or days without meaningful precipitation is mostly confined to the Cimarron an Canadian River basins. The TX Panhandle has been receiving a surprisingly high amount of precipitation. All in all, pretty standard for the time of year.

    4c7c1b94b203b74022255131b87ec472.png
     
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  2. Jason Foster

    Jason Foster Member

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    This may be good news, especially for dryline chasers. Lets see how it holds out. Like to see less dryness over western OK & KS too. I need to refresh and update myself on other factors like El Nino/Southern Oscillation, GOM SSTs, Pacific SSTs and whatever else (been a while so I'm kinda clueless really).
     
  3. Mike Marz

    Mike Marz Member

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    c1e092d4166228b3a961ca5d5864d4d7.gif
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    The long range models are in pretty good agreement, with a potential severe weather event for this upcoming weekend for parts of Dixie Alley and along the Gulf. The SPC has highlighted this potential in their day 4-8 outlook. Although there could still be timing and location issues, it will definitely be interesting to keep an eye on this situation throughout this week. It appears right now that shear and instability could be adequate for a decent event. Obviously the location is not ideal for chasing, and it is still a bit too early to get into any of the finer details, at the very least, it is something to watch during the peak of our SDS...
     
    #3 Mike Marz, Jan 17, 2017
    Last edited: Jan 17, 2017
  4. Robert Forry

    Robert Forry Member

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    Mobile sounding for Saturday afternoon (1/21) looking loaded gunnish. Good post about the drought @James good to see those areas getting that moisture after a while of being exceptionally dry. Hopefully that bodes well for the upcoming chase season :)
    saturday.PNG
     
  5. Jake Orosi

    Jake Orosi Member

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    Turned out to be a tragic weekend for many in the Gulf region. Weather-wise, it seemed like an interesting early-year event. I wonder what it has to suggest, if anything, about the coming chase season.
     
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  6. Randy Jennings

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    We are off to an ingesting start for sure. I too was wondering what this might mean for the upcoming season, so I did some research. Many of you are likely aware of the Allen, Tippett, Sobel study published in Nature Geoscience in 2015 (Influence of the El Niño/Southern Oscillation on tornado and hail frequency in the United States http://www.nature.com/ngeo/journal/v8/n4/full/ngeo2385.html). While you have to pay for full access (or find a library that subscribes), the abstract gives you some clues: “We show that fewer tornadoes and hail events occur over the central US during El Niño and conversely more occur during La Niña conditions. Moreover, winter ENSO conditions often persist into early spring, and consequently the winter ENSO state can be used to predict changes in tornado and hail frequency during the following spring.”

    Cook and Schaefer point out that “researchers do not agree on the seasonal and monthly variations of tornado activity as a function of ENSO phase” in their paper (The Relation of El Nino Southern Oscillation (ENSO) to Winter Tornado Outbreaks, http://www.spc.noaa.gov/publications/cook/ensowntr.pdf) but do conclude “a statistically significant trend for stronger, longer-track tornadoes to occur during LN and neutral winters compared to EN winters is seen.” They go on to note that the most likely zones for tornados vary depending on ENSO phase.

    So given our current LN phase and the results of those two studies, one could reasonably hypothesis that we would see stronger longer-track tornados, more tornados in the spring, and the zone of most activity would occur “in a southwest to northeast belt that stretches from the Mississippi Delta to the Central Great Lakes region”.

    That may not be a good hypothesis after all. NOAA’s Climate Prediction Center says “a transition to ENSO-neutral is expected to occur by February 2017, with ENSO-neutral then continuing through the first half of 2017.” (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_disc_jan2017/ensodisc.shtml).

    So I took a look at some localized data (http://www.weather.gov/fwd/fwdtornadoes) to see what I could learn form that. In 2017, there have already been 6 tornados in January in the FWD CWA. Going back to 1950, only 11 years prior to 2017 had January tornados. Of those years, 5 where EN, 3 where LN, and 3 where N (a surprise based on the Allen study). The average number of tornados per year in the FWD CWA is 25.5. Of the 11 years with Jan tornados, 5 where bellow average years and 6 are above average years. It is important to note that the lowest bellow average year was only bellow by 5 tornados. Of the above average years, only one year has 1 standard deviation above average (1996 which had 51). 3 years had 10, 12, and 13 more tornados each and the other 2 where barely above average. I should note that as one goes back towards 1950 in the pre cell phone days, the number of tornados is likely underreported.

    Bottom line to me – this is fun to talk about, and I remain optimistic about the coming season, but I don’t think we can draw too many conclusions right now. For one, we may be ENSO neutral by spring. For another, the effects of ENSO on tornado counts in any given area are still a subject of great debate. We wouldn’t use the GFS 384 hours out to pick a target area, so we probably should not get too excited or depressed over the chase season this early either.
     
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  7. NealRasmussen

    NealRasmussen Member

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    It's all in the snowpack I think. ;)
    I think we need,by law, all farmers to turn on their center-pivot irrigation systems with snow making nozzles when the temp is low enough. Blanket Kansas!
     
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  8. Paul Knightley

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    I think there are 2 overall 'things' to consider when looking at the upcoming chase season: 1) The overall season, and 2) When you might chase.

    For 1), we can sometimes get a reasonable impression of the overall chances of it being rather active or less active, by looking at the various analogues, large-scale climate indicators (e.g. PDO, ENSO, etc), as well as models. However, unless you have the relative luxury of being able to chase whenever you can (or a close approximation to this), you'll more likely be interested in a specific window, especially if, like me, you have to plan months in advance. In that case, the overall season's activity is rather overshadowed by unresolvable sub-seasonal effects. E.g. you could be in the middle of the most active season for years, but have a 2 week period of upper ridging, simply due to the state of the atmosphere at that point in time. If you time your trip with this, because you have to plan far ahead, then the season has not been a good one for you!
     
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  9. Jeff Duda

    Jeff Duda Arbitrarily calls almost every setup a bust
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    For those who don't know, a once active member runs a sub-seasonal forecasting experiment for tornadoes, called ERTAF. He will be starting again in March. You can read up on the methodology and check the forecasts here: http://weather.cod.edu/~vgensini/ertaf/
     
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  10. Brandon Centeno

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    I will be following this. I listened to his talk at SLS and found it very intriguing.
     
  11. Jeff Duda

    Jeff Duda Arbitrarily calls almost every setup a bust
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    It's probably not too early to begin considering how low-frequency seasonal and even sub-seasonal patterns may be setting up to provide some degree of predictability for how the 2017 chase season will go. One particular feature I tend to pay attention to is the MJO, which can be monitored on the CPC website here (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml). An MWR paper from a few years ago pointed to a link between MJO phase 2 and increased violent tornado outbreaks during March-May (and a reduction in tornado outbreaks during phase 8). Great! So how do we know when the MJO will be in phase 2? MJO prediction is not easy, nor particularly skillful, so that's still up for debate. You kind of still have to monitor current MJO conditions and perhaps operate under the assumption that if an MJO pulse begins in phase 1, then phase 2 is not far away, or that if a current MJO pulse is already on phase 3 or later, then phase 2 is probably a long way away. Since the MJO takes 30-60 days to complete, there's basically only going to be one cycle during the spring season.

    The final requirement described in the paper above is that you need to have a supportive large-scale setup already present when phase 2 of the MJO occurs. This pattern (Fig. 7 in the paper) features anomalous ridging at 300-mb across the western north Pacific and anomalous troughing across the western US (with some mildly anomalous ridging across the southeast US).

    The current MJO status: RMM > 1.0, which means there is actually some distinguishable MJO signal above the noise level, and it appears to be crossing over from phase 4 into phase 5. G(E)FS forecasts call for the signal to strengthen and progress across phases 6 and 7 and into phase 8 by the mid-late part of February. Should it continue (once an oscillation is started I don't think there's any guarantee it will continue to progress across the rest of the phases) at a constant pace, it may be in phase 2 by early March, which may suggest an increased potential for early season tornado events. However, that is pure speculation at this time and is based on some really long range forecasts. It's best to continue to monitor the MJO index (RMM) throughout the rest of February and into March to see what help (or hindrance) the MJO may offer for 2017's traditional season.
     
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  12. Brandon Centeno

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    Good stuff.. saw a presentation at SLS regarding MJO phases and tornado activity. Gensini I think does one using the global wind oscillation or whatever..

    Extended range model forecasts don't show any particularly harsh gulf clearings occurring anytime soon, so I could buy an early-mid March setup happening *if* the general pattern persisted.
     
  13. Jeff Duda

    Jeff Duda Arbitrarily calls almost every setup a bust
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    That's a good point about Gulf clearing. I recall seeing an extended range forecast suggesting the second half of February would be very much above average in terms of temperature CONUSwide, which would suggest a minimum, if not an absence, of fronts making it to the Gulf. CPC's outlooks for the next several weeks concur...

    6-10 day temperature outlook:
    610temp.new.gif

    8-14 day temperature outlook:
    814temp.new.gif

    3-4 week temperature outlook
    WK34temp.gif

    70% probability of above average temps at 3-4 weeks with this kind of lead time makes me lol. These are very strong indications of a warm end to February. Now, they're also paired with solid probabilities of below average precipitation, and there is an ongoing drought across parts of the southern plains, especially Oklahoma. So moisture could certainly ruin any early season setups. We will just have to wait and see.
     
  14. Jeff House

    Jeff House Member

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    Agree MJO is a big player but it is too early to get into those weeds. ENSO has some value, including transition between phases: Trans_Nino_Index_(Lee_etal)_version2.0.pdf

    Past studies suggested La Nina is active from the Plains through the Southeast; then, El Nino is active early season Deep South and late season Upper Midwest, but less active heart of the Alley. Study above suggests those correlations are weak, esp if not considering the evolution of ENSO from the prior fall/winter into the spring of interest.

    Trans Nino Index also looks at the in between phases. El Nino ending early may allow more activity than persistent Nino. La Nina is still slightly more active than normal Midwest to Southeast. However decaying La Nina may be the most active relative to normal in the Plains and Midwest. La Nina is already decaying by SSTs. Atmospheric response was always stronger than SSTs alone would imply. A slow decay in the atmosphere matches North American charts in the paper.
     
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    #14 Jeff House, Feb 8, 2017
    Last edited: Feb 8, 2017
  15. Kevin R Burgess

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    I'am curious to know if Kelvin Waves have any influence,along w/ the MJO,on Severe Wx/Tornadoes ?
     
  16. Brett Roberts

    Brett Roberts Experienced Member

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    A couple years ago I developed a crude scoring methodology for previous chase seasons going back to 1955 using Storm Data (tornado and hail reports, specifically). I then ran simple linear regressions on the chase season scores against various climate/teleconnection indices. Looking at a 3-4 month lead time, the Arctic Oscillation (AO) had the largest correlation with the subsequent chase season's score. It's a positive correlation, so +AO values during the winter are associated with "better" chase seasons.

    So far this winter, the AO has been dominantly positive. In fact, we're just now entering our first sustained negative period since mid autumn! If the GEFS forecasts for the next 2 weeks are reasonably accurate, we should end meteorological winter with a mean AO somewhere around +1.0. All else being equal, this is a good sign for the upcoming season, and particularly the early season.

    Of course, there are tons of caveats, including the relatively small sample size. The correlation is not all that strong, anyway (R ~ 0.25 to 0.3, depending on the region of interest). But it's somewhat comforting to know that over the last 60 years, most of the completely dreadful Plains chase seasons occurred following dominantly -AO winters.

    With all that said, drought is certainly becoming a concern, especially for the High Plains. The past two years, drought looked like it would be a problem during the winter and early spring, but slow-moving closed lows in April saved the day just in time. So you never know. Unfortunately, the ENSO signal -- weak negative ONI likely transitioning toward weak to moderate positive values during the spring -- is not particularly encouraging, either. Some recent seasons with a similar progression include 2006, 2009, and 2012...
     
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  17. Brandon Centeno

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    Way too early to be talking about much, but it seems western troughing will take place late next weekend into early next week, indicated by both GEFS and EPS. GFS ensemble is shallower and faster/farther east, but EPS (is EPS on tropical tidbits the true ensemble mean or just one member from the ensemble?) shows several days of return flow with a wide warm sector and strong low pressure system in Lee of the Rockies. I would certainly keep an eye on this time frame for a bit. 9b4f1282fe59401522e776ce06a134e2.png

    Seems more like an early May/late April pattern than a February pattern.
     
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  18. Jeff Duda

    Jeff Duda Arbitrarily calls almost every setup a bust
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    You can generally tell whether an ensemble product is the mean or a member by examining the structure of the field. As smoothed and "textbook" as the 500 mb heights in your image look, that's got to be the ensemble mean. Ensemble mean fields are filtered and smoothed compared to what any given ensemble member will look like.
     
  19. Jeff Duda

    Jeff Duda Arbitrarily calls almost every setup a bust
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    Looks like the MJO pulse that was beginning when I posted recently has really blossomed into an event. Moreover, recent forecasts are consistently showing a significant strengthening as the event enters phase 8, with a rapid die off afterward. Therefore this MJO cycle will probably not directly impact the early season for severe weather, but it is interesting to watch nonetheless.

    ensplume_small.gif
     
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  20. Brandon Centeno

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    That's what I thought, especially when comparing to the deterministic EC. I am just impressed by the signal so far ahead for a robust system in the lee of the rockies, with what appears to be a pretty broad warm sector.

    In contrast, the GFS/GEFS is much more progressive and really a non-event for the plains. Moisture, this far out, looks to be an issue given strong frontal intrusion currently progged, but I will be watching.
     
  21. Brandon Centeno

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    Unsurprisingly, while there will probably be some marginal severe risk in portions of Texas, what will now most likely be a highly amplified system producing heavy rain over the southern plains will of course be a non-event.

    Attention turns now to late next week. By then, we should be entering (or in) phases 8-2 of the AAM/GWO with strong troughing pushing into the rockies. W/SW flow aloft will possibly transport weak EML over C/S plains. Given lingering effects of a cutoff low, and time of year, moisture will be limited, however looks like the trend may be to moisten with time. Additionally, if model solutions are to slow (slower translation of wave) then moisture return could actually be better. In any case, looks like next week could be something to watch, but climo says probably not.
     
  22. Jason Gassner

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    I would say we got hammered in Texas. I'm not sure if this is what you were referring to, but 9 confirmed tornadoes...highest rating an EF2.
     
  23. Tim Paitz

    Tim Paitz Member

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    Here's the current state of the ENSO.

    c51d7e83308b166001a180f7339df1f4.gif


    It's almost looking like an El Niño in the making (mainly in February). The SST's need to be .5° C. above average in the Niño 3+4 for 3 months to be declared an El Niño if I'm not mistaken.
     
  24. Jeff Duda

    Jeff Duda Arbitrarily calls almost every setup a bust
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    A lot of the seasonal forecast models are indicating a rebound to a +ENSO state (i.e., El Nino) arriving as early as this summer.
    figure4.gif
    nino34Seaadj.gif

    A developing El Nino is likely not going to have any major impact on the quality of the 2017 spring season, though.

    EDIT: I should add that we're punching into the spring predictability barrier right now, too, so take these forecasts with a grain of salt.
     
    #24 Jeff Duda, Feb 22, 2017
    Last edited: Feb 23, 2017
  25. Michael Snyder

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    Just for clarification: El Nino would need 5 consecutive overlapping 3-month periods.

    Check out 2008-2009 almost La Nina, the Nov-Mar period missed being classified as La Nina by 0.1, the Feb/Mar/Apr reading came in just over with (-0.4).
     

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