2017-03-26 EVENT: KS/OK/TX

Discussion in 'Target Area' started by Brian McKibben, Mar 22, 2017.

  1. Brian McKibben

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    Not sure if moisture will make it to KS but figured, I would include them just in case.

    GFS and ECMWF have been consistent for several runs now showing a trough moving across the region on Sunday. One of the big limiting issues will be moisture.

    Surface
    Cyclogenesis begins overnight Saturday in SE Colorado and strengthens on Sunday as low moves into TX/OK panhandles. This allows winds to back to SSE east of the DL in the warm sector in OK and N TX. The warm front sets up in southern KS. Daytime highs look to be in the mid to upper 70s.

    Friday's system pushes the 60° isodrosotherm all the way to the gulf coast where it stays until 06z sunday. Then rapid moisture advection brings mid 60 Tds to DFW and low 60s to KS/OK border by 00z Monday. It will be key to watch how far south the moisture goes with Friday's system.

    The theta e tongue sets up along and east of I-35 from DFW to Wichita.

    00ac26df2016b06b5bb1552e0838f5ee.png

    Upper Level:

    Negatively titled 500 hPa trough moves across the region Sunday afternoon and evening. Looking at 50-60 knots from the SW.

    11804b85f22bffeec74a0dcddede9944.png

    At 850 hPa, the warm sector is overspread with 40-50 kts from about 190°. Needless to say low level shear should be more than adequate for tornadoes. 0-1km helicity greater than 300 m2/s2 look likely. And at this time I don't see any problems with VBV wind profiles.

    ec155b777dfd8d4eaae475ecf87a29ca.png

    Conclusion:

    Potential is there for some decent severe weather including tornadoes. The 500 hPa trough comes in right behind the friday trough so we have a short wavelength. This will potentially limit the available moisture. But with that said the friday system doesn't clear the Gulf and leaves the moisture on the coast. So confidence is medium that moisture will at least make it to north TX. Depending on surface temps and forcing I wonder if we will have any capping issues. Too far out to tell, but I will be keeping an eye on the models and the 12z NAM on Thur.

    Special Treat:

    Sounding for north Dallas

    b348e822b6d9066e218e33aa117c217c.png
     
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  2. Jeff Duda

    Jeff Duda Resident meteorological expert
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    The GEFS has remained rather uncertain as to the shape of the jet associated with this trough. As a result, there remains considerable uncertainty as to whether a widespread severe threat will materialze, and if so, where. Also of concern is moisture quality. GFS forecasts have been fairly consistent as of late of getting some 60+ dews into Oklahoma, but it's "just in time" kind of moisture.

    Personally I'm not too encouraged by what I'm seeing, as the event has also trended further east, mostly east of I-35. So an uncertain moisture scenario and uncertain shear in a less-than-favorable chase terrain doesn't get me too excited. But we will see what happens.
     
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  3. Gabe Garfield

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    The big issues to my mind are: wave timing and moisture return.

    The GFS moves the 500 mb wave into the Plains a little too early, which could result in too many storms. It also screws up the hodographs by creating a veer-back-veer profile (though the jury is still out as to whether VBV is actually "bad"). Additionally, the moisture is a question mark. As Jeff mentioned, it gets there "just in time" in the GFS. Even with limited moisture, however, I think we could see a few tornadoes: low-level shear is spectacular almost everywhere in the risk area. And, if we can realize mid-60's Tds (as the GFS forecasts), strong tornadoes would be possible.
     
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  4. Stephen J

    Stephen J Lurker

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    With what Jeff and Gabe has already noted about the "Just in time" moisture issues and the timing of the 500mb wave is a huge question with this system. It is also interesting to note that the EURO model has a slightly slower solution and ever so slightly to the west of what the GFS operational shows. One of those classic "Could go big" or "Bust" written all over it. Also wanted to note that the capping could be an issue as well with GFS showing the CIN filling back in at 00z and if you look back to 21z, it has a wide open hole just east of the dryline.

    I think that if we can get the 500mb wave (Which GFS usually tends to be too progressive) and the deep moisture to return all the way north into Central Oklahoma. This could yield to a very big day from OUN down to DFW along and just west of I-35. Definitely worth getting a little tingly inside! I've heard Turner Fallis nice this time of year, and may take a look see down there on Sunday.
     
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  5. Ethan Schisler

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    This event has been kind of reminding me of 2010-05-10 except on a much lesser magnitude than the parameters were with that event (I think someone else may have mentioned this somewhere else), with the nature of this compact wave. As of right now, quality of moisture return is the biggest question in my mind. If we can get the moisture, then definitely could see a setup where a few tornadoes are possible. Not to sing to the choir or report what anyone else has already said. It will be interesting to keep an eye on.
     
  6. Trey Thee

    Trey Thee EF2

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    My biggest concern at this point is definitely with the moisture. It seems the last couple years models have been overly aggressive with bringing in moisture "just in time" which turns into "not quite fast enough". The shortwave also moves out a touch quick as was previously mentioned, though I've seen shortwave timing change a reasonable amount in a short period of time so I'm not too concerned with that until we get into Friday or Saturday morning.

    Moisture issue may become obvious once Friday's system moves through.

    It seems that we're on the cusp of a potentially big event for late March. DFW in particular may have some real threats to deal with, moisture return will likely make the red river putting the entire metroplex potentially in the mix for svr weather.
     
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  7. Michael Snyder

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    Seeing the NAM show DPs in the low 40's through much of north TX at 06Z Sun Morning is a tough pill to swallow. Thinking about flying down, would be a good trial run for 2017, but it could easily turn out to be one of those "almost" good enough moisture events, as everyone else has said.

    The surge of moisture on the GFS from 12z to 18Z Sunday just seems a bit unrealistic.
     
  8. Tim Supinie

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    Many people have pointed out the rapidity of the moisture return on Sunday morning. Just based on tonight's 00Z GFS solution, I'd argue the moisture has plenty of time to get here. Tracking the 10 C isodrosotherm at 925 mb, it moves 350 km in 6 hrs, or about 30 kts, which is pretty close to what the wind speed at 925 is. The fact that the moisture moves consistently with advection gives me confidence that it's realistic and not some funny business with the GFS land surface model. I just used the 12-18Z Sunday time period, but the speed of moisture return is consistent from 00Z Sunday morning (Saturday night) onward.

    925td.us_sc_annot.png

    Again, this is the GFS forecast verbatim, so there's caveats. If the boundary from the Friday wave stalls out farther south than the GFS thinks, then this might change. However, even in that case the nocturnal boundary layer jet that develops on Saturday night might save us.

    The fly in the ointment with these rapid moisture return events always seems to be cloud cover, as warm air advection tends to go with moisture advection. Verbatim, the GFS slacks off on WAA between 12Z and 00Z, suggesting it thinks any clouds should break up by go-time. I'm not sure that's reliable in a 96-hr forecast, so I'll say that's still on the table.

    There's also still some placement and structure issues to be worked out with the mid-level shortwave trough, per the ensembles (even though this morning's 12Z GFS and ECMWF agreed ... pretty well, actually, on the location and structure of the wave at 12Z Sunday morning). IMO, the cloud cover and the wave placement are the biggest unknowns with Sunday.
     
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  9. Robert Forry

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    All great points to consider before hoping in a car and driving 14 hours to an early season target that may or may not verify. Am really curious to see what the 12Z NAM today does with this as the GFS has consistently advertised the low/quality moisture concerns after the last several runs. Another concern I've noticed on some of the soundings is saturation in the mid levels, though low level shear looks great! Tim's point above is great and has me leaning toward making a rocket run.
     
  10. Tim Supinie

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    And now the 12Z NAM comes in and makes me a moron. Boundary stalls out much farther south than the GFS. So much so that the LLJ doesn't pick it up until 12Z Sunday morning, which is definitely too late. There's also some drying at 925 mb off the Gulf coast between 21Z Saturday and 03Z Sunday that delays the moisture return. Maybe related to the NAM's shallow cumulus scheme? Maybe some descent bringing down dry air from aloft? I'm not sure. Whatever, I'm getting too into the weeds on a 72-hr NAM forecast ...
     
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    #10 Tim Supinie, Mar 23, 2017
    Last edited: Mar 23, 2017
  11. Tim Marquis

    Tim Marquis Guest

    To me, there's a lot of mode failures here. Having two shortwaves back to back always causes concerns about moisture quality but for me, with how compact this shortwave, the timing has me most concerned.

    The GFS continues to be the most progressive of the bunch but we've all seen in the past how it slows down 48 hours or so closer to the event. The ECMWF nails having a stout surface low centered over Altus meaning a I35 corridor event is most likely. However, any delay in the ejection could lead to the moisture being misaligned with the main forcing.

    All in all we are definitely deep diving into this setup because well its the first one in OK and I think it certainly has the potential to be a tornadic day but overall the risk of it not is higher.
     
  12. Jeff Duda

    Jeff Duda Resident meteorological expert
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    Really not encouraged by the 12Z NAM and 09Z SREF. Moisture return not only questionable, but doubtful. Only a few members even put 60+ dews in DFW, and the ensemble mean is in the low 50s, and it's much worse further north. Also, for some reason the 12Z NAM occludes the wave during the day so that by 00Z the heights fill in, gradients weaken, and the wind fields fall apart. The 12Z GFS does not do this, so go figure.

    Since this is basically in my backyard I can afford to wait until Sunday afternoon to decide to chase it, but if I had to make plans right now I'd be unlikely to make the effort.
     
  13. Gabe Garfield

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    I'm somewhat encouraged by the 12Z 24 March NAM. Though the "juice" doesn't quite make it up to Oklahoma, the dewpoints are forecast to be in the mid-60's in the Dallas-Ft Worth metro area by 00Z 27 March. Given the pretty outrageous shear profiles and decent lapse rates, conditions would be favorable for supercells and tornadoes if that kind of moisture were to materialize. Additionally, the forcing is a bit more subtle south of the Red River, which might favor more isolated storms.

    However, the 6Z GFS was pretty stingy with the moisture, bringing only mid-50's Tds to N TX. If that's the case, in the words of the late, great Bill Paxton, "Game over man, game over!"
     
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  14. Trey Thee

    Trey Thee EF2

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    Enhanced risk up for tomorrow in central OK. If DP's get to the low 60's its game on for a tornado threat IMO.
    However, the bigger oddity in my mind is the lack of enhanced risk for the DFW metroplex. Forecast soundings look better, moisture return is better, instability is higher, at this point I it seems the DFW area justifies more of a 30% than does central OK.
    One thing to note the NAM has been trending an uptick in moisture between 18 and 00Z tomorrow. The trend is your friend?

    This is right in my backyard so we'll see how things unfold, I'm particularly interested to see how today evolves. That will be critical in setting up moisture return for tomorrow.
     
  15. Tim Supinie

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    The forcing is more subtle the farther south you get, so they're probably thinking the coverage will be less in the DFW area. Remember that SPC risk areas are primarily about density of severe reports, not intensity or chaseability.

    I'm encouraged by the 25/12Z GFS and NAM runs. Both of them bring the 60 F isodrosotherm into southern OK by 00Z tomorrow evening, though I'll be monitoring obs with the moisture and its transport this evening.

    One other potential issue that I forgot to mention earlier is that models have been busting badly on the mixing. They haven't been mixing deep enough, which results in deeper, drier PBLs than the models project. This is most pronounced in central OK, though is probably occurring to a certain degree everywhere, and is almost certainly related to the drought and time since significant rainfall. So be aware that areas that see significant sunshine tomorrow are also liable to have the moisture mix out, too.
     
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  16. Trey Thee

    Trey Thee EF2

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    Tim that is an excellent point regarding forcing and coverage. Forcing does look weaker down there.

    Your point about mixing is also a good one and not something I had really given any thought to but it beats keeping in mind as we think about tomorrow.

    Sent from my Pixel XL using Stormtrack mobile app
     
  17. Jeff Duda

    Jeff Duda Resident meteorological expert
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    There's been a significant uptick in SREF moisture over the last several cycles. I'm still skeptical on it verifying, though. Also, the 03Z SREF is significantly at odds with the 00Z NCAR ensemble, which keeps moisture well reduced compared to the NAM:

    SREF_OKC.png

    03Z_SREF_OKC.png

    NCAR_OKC_qv.png
     
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  18. Trey Thee

    Trey Thee EF2

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    If OKC only makes it to the low 50s you can scratch any tor threat, it'll be wind/hail. Ultimately we have to find a way to open the window to the gulf and get some moisture here...

    Jeff what do you make of the uptick in moisture showing up on the models the last few runs? You said you're a bit skeptical, why is that? Is it as simple as the models have been over forecasting moisture with system after system for a long time now?
     
  19. Troy Scheiber

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    DP's in south Oklahoma look to be 55-60 around 0z according to latest models I looked at. Gambling that ML moisture pushes through the DFW area to OK earlier than anticipated - Cape 1.5k. Not chasing yet this year but if I were tomorrow, I'd center around the Ardmore area and see what happens to SPC warnings along the I-35 corridor.
    Troy


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  20. Greg Blumberg

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    After perusing the 12 UTC NAM and GFS forecasts, there are a few primary differences that I've noticed. I much more like the GFS 18-00 UTC forecast, as it has a much stronger lower level wind field than the NAM, which seems to be nearly doubling the 0-3 km SRH at 21 UTC in southern Oklahoma. Deep layer shear looks good in both forecasts and there is sufficient CAPE (>1000 J/kg MLCAPE) in southern Oklahoma. In addition, at 21 UTC the GFS at Purcell, OK has stronger lift throughout the column (see first image), which has the benefit of eroding the capping inversion by 21 UTC. This is related to the fact that the GFS solution has precipitation break out at 21 UTC, where as the NAM has the precipitation holding off till 3 UTC. Although I should add that the NAM doesn't have any sufficient moistening in the mid levels after 21 UTC, which needed to activate the BMJ convective parameterization.

    Pairing forecast soundings from ahead and behind the dry line from the GFS and NAM forecasts suggest that the dry line circulation will be sufficiently deep enough to get parcels ahead of the dry line past their MLLFCs, which is a very good thing if we are questioning the possibility of convection initiation. From this, I am optimistic that storms will develop, but the issues of NWP recently under-doing the mixing Tim Supinie has brought up here and on Twitter constantly nag me and push me to adjust the NWP low-level moisture forecasts to be drier. However, right now I can see 1-2 supercells developing from this setup in southern OK/northern TX, at least from the GFS forecast. In particular, the Ardmore, OK 21-00 UTC GFS forecast soundings look incredible. Now, if the surface dew point drops below 55 F tomorrow, I will be very worried about whether or not storms will actually develop and sustain themselves. I can be a little pessimistic about the moisture quality, but right now I'm feeling cautiously optimistic about tomorrow.

    One thing that does stand out is that the NAM at 16-18 UTC has an odd moisture profile (with rapid moistening and drying with height near 850 mb in second image, although the 17 UTC sounding looks better) near the top of the boundary layer that stands out to me as suspicious. My guess is that this must be due to some of the parameterizations in the NAM, and given how unrealistic the profile is (I've never seen something like that in nature), I suspect that the NAM's moisture evolution may be highly dependent upon the parameterization schemes.

    P.S. With respect to the NCAR ensemble run, I wouldn't pay too much attention to it, as most if not all of the members have already busted the 18 UTC 2-m dewpoint temperature in southern Texas by nearly 10-20 F, and suggests that any moisture advected from that area northwards during the day or tomorrow will be drier than reality. Per other forecasts, the moisture in southern Texas plays a critical role in moistening up the southern Oklahoma/northern Texas areas as it gets advected northwards by the low-level jet stream. Another thing noted by Tim Supinie (who I've been discussing the forecast with for the past few hours) is that the 2-m dewpoint at Brownsville is running above the mean of 9 UTC SREF forecasts. This may also suggest that the 9 UTC SREF members may be also under-doing how moist the source region is for our moisture.

    2017032621_PRC.png

    2017032618_PRC.png
     
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    #20 Greg Blumberg, Mar 25, 2017
    Last edited: Mar 25, 2017
  21. Robert Rohloff

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    Greg, we have seen some very nice DP readings in OK since the start of the year, 70 in Feb. Do the models bias towards a normal for time of the year? If they do would it be a bias towards under estimating the levels?
     
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  22. Jeff Duda

    Jeff Duda Resident meteorological expert
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    @Greg Blumberg is right that the 00Z NCAR ensemble has severely underpredicted dewpoints in southern TX as of this afternoon. However, going by the math, the winds are only forecast to switch around to "return" flow sometime this evening (perhaps late) and winds in that area are not forecast to be particularly strong (generally 10 kts or less through 12-15Z tomorrow). So the math on advection allows for movement of the higher moisture isodrosotherms of about 250-300 mi northward progression from where they are when winds switch around, which, based on current obs, puts the leading edge of moisture somewhere near the I-20 latitude (DFW area) by 00Z tomorrow, or AT BEST (assuming moisture coming from Houston switches around at the same time) the Red River. The sensitivity of my math to errors in the wind speeds or timing for return does leave a window where moisture gets into southern Oklahoma, however. Also, I have seen moisture return even faster than suggested by the NAM in recent times, so it's not impossible that moisture could make it, although if I recall, those types of events were later in the spring after green-up was long since completed and full ET was in place. This being only late March and it being so dry across much of the southern Plains lately makes me wonder if ET is going to have as strong an impact as it would later in the year.

    We'll see if I'm wrong. I certainly could be. But my argument above is mathematically and scientifically defensible.
     
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  23. Damon Lewis

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    HRRRx has had nice 12z and 18z convective runs for C/E OK.

    b2cec23c26bf056850fedcfcadd3402b.png
     
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  24. Ethan Schisler

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    While pretty to look at, these 3km NAM and HRRR graphics don't mean anything if the moisture they are advertising doesn't make it up in time for the main show. The latest run of the HRRR which goes out to 10am tomorrow, shows the nearest 60 degree dew points about 3-4 counties south of the Red River. Will this translate into moisture making it at least into Southern Oklahoma by 00z? Who knows, and even then with such a rapid moisture return, the depth of the moisture is likely going to be coming into question. I'm about 40/60 on chasing this event right now as it is, normally I wouldn't consider a one-day haul for such an event, however Monday may be decent in Arkansas and that would be.......sorta.....on the way home lol. Or I may hold out for the next system on TUES-WED which looking at guidance taken at verbatim, holds chase potential as well, especially over the Western Texas/Caprock region....but that is a discussion for another thread.
     
  25. Damon Lewis

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    I agree 100%. My confidence in moisture return with decent depth is not that high and the HRRRx is really the only one depicting that type of convection.
    I just posted it as it was two runs in a row and gave me a little hope, LOL..

    I'm 50/50 on chasing tomorrow. We'll be working on buddies chase vehicle tomorrow afternoon at his house and I'll have mine there so we'll play it pending how it looks around 3 tomorrow and head out from Tulsa if it looks decent.
    We have some new tech we're wanting to try so we're antsy to get out on something good.
     
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