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Posts posted by andyhb

  1. 2 hours ago, Powerball said:

    Or, it could just be like the past few years:


    At this point, I'll be happy with just getting another derecho in the middle of June (ala 2019). I just want out of this pattern of BN temps and grungy / gloomy skies. 

    You live in Addison TX. Have you not been paying attention to the past week in N TX?

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  2. Day has some similarities to 4/22 (Springer/Madill) last year being right at the base of the trough with cold air aloft promoting a lot of 0-3 km CAPE and strong updraft accelerations. Ingredients that I'd look for more of are low level flow/moisture depth and also the eastward extent of the warm sector. I'm wondering if some warmer temps closer to I-35 could promote a threat closer to the main LLJ axis, which would raise the tornado threat for DFW north to OKC.

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  3. Well, safe to say this could be a pretty big event. Convective evolution/mode concerns notwithstanding, there seems to be a consensus across all of guidance for hodographs supportive of long-lived supercells with long tracked tornadoes as early as 15-18z in LA/MS. The degree of low-level moisture is on the high side for this time of year, and I wonder if there may be some subsidence in the late morning following the passage of a potential lead shortwave that could help to suppress junk convection.

    Any discrete storm in the warm sector that manages to root in that boundary layer by early afternoon is likely going to be a problem. Now it's a question of what wrinkles the mesoscale throws in (and whether the NAM comes around more to the potent solutions suggested by the globals, particularly the UK and Euro).

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  4. Just now, jpeters3 said:

    Honestly, 5-20 is still a bit of a head scratcher for me.  I understand the issue with large scale lift, but large scale lift doesn't trigger convection.  It simply makes the environment more favorable by steepening lapse rates and potentially reducing CIN.

    An interesting result that trending in recent research is that, for CI to really go, you need wide enough sub-cloud updrafts.  In the absence of other forcing mechanisms (like OFBs, terrain, front, dryline), the size of sub-cloud updrafts scales with the PBL depth.  In the case of 5-20, the PBL was < 1 km deep, whereas the "threshold" sub-cloud updraft width for making sustained deep updrafts is generally larger than 1 km (in radius).  So my hypothesis is that the PBL convection just couldn't cut it on that day.  I have meant to write a paper on this, but i never seem to have the time.

    Based on my experience being out there in SW OK as storms tried to develop, this was the case. Every attempt became a turkey tower, and part of it was likely due to all of the smoke in the warm sector limiting insolation (and the capping being stronger than the models had).

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  5. Just now, jpeters3 said:

    I wouldn't call this bearish on a cleaner evolution.  The lack cohesive of UH tracks in the warm sector suggests shallower (than supercells), nonsteady convection.

    I was referring to the 12z runs here. The 18z was definitely less favorable, although there still seems to be some attempts at warm sector initiation.

  6. 7 minutes ago, jpeters3 said:

    I'm not arguing against a significant severe event.  Given the volatility of the environment, QLCS tornadoes, and perhaps some isolated supercell tornadoes, are likely if the current CAMs play out.  But they aren't showing a classic tornado outbreak by any means. 

    No one said you did.

    I'm just saying that I don't think the 12z CAMs were really a trend one way or another towards a really muted event ala 5/20/2019. If anything, the HRRR being a little more bearish than some of the WRFs might increase my confidence in a cleaner evolution, lol.

  7. 2 hours ago, jpeters3 said:

    I think the main question is storm mode.  CAMS seem to be trending toward a classic southeastern US "grunge fest" with widespread nonsupercellular convection in the warm sector, and a QLCS along the front.  This could therefore pan out like 5-20-19 in the plains, with an impressive environment but a lack of tornadic supercells.

    Main question in the SE usually is storm mode given lack of more obvious boundaries, but I'm not so sure that 12z CAM suite was as "grungey" as it would appear, especially a couple of the WRFs. The aggregate/average of them as depicted by the 12z HREF would likely be a significant severe event, with both supercells and bowing line segments.

    The big question is what does the storm mode look like post-21z when the low-level shear increases significantly. If there are still supercells ongoing by 00z and into the nocturnal period, watch out. The pseudo-cold core regime nearer to the upper low in AR/MO is also worth watching should it be able to destabilize sufficiently.

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  8. Wednesday has the potential to be a widespread severe weather outbreak across the Lower MS Valley/Mid South/ TN Valley/even Lower OH Valley. An expansive EML and high BL moisture content yielding a wide region of destabilization, large area of favorable shear, and moderate forcing for ascent could yield multiple corridors of enhanced potential. Still some uncertainty surrounding the low level wind fields and northward extent, but the signals are rather troubling.

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  9. 1 hour ago, Hoosier said:

    Well, if it is based on "extensive social science research with partners and the public", then I'll wait to pass judgment. 

    People like us are a very small slice of the public.  If the changes help with the messaging for the masses, then that is a good thing.


    Ignoring what weather weenies like us want in favor of what is simpler for the public to understand is the whole purpose of working with social scientists. I don't see any need to trash this decision until we see actual results from the change.

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  10. On 2/19/2021 at 2:57 PM, andyhb said:

    Look on the ensembles heading into March would suggest the potential for a warmer/wet period, with the possibility of severe wx somewhere, particularly east of the Plains. Again, this is tied to the retrograding longwave pattern across North America and the Eastern Pacific.


    Can be seen here in the 12z EPS mean, watch the behavior of the ridging that generally starts over the eastern Pacific, whose retrogression eventually leads to the jet dropping into the Pacific NW.

    Or we could just drop into split flow for the umpteenth time in the past decade and erase any chance for severe/a decent spring pattern, smh.

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