Stx_Thunder

Seeing new, fairly strong thunder development with the dry line/front closer to Abilene area right now with one embedded supercell near Coleman that was apparently producing 2” hail just a short time ago. The more reliable ARW2 and NSSL convective models are showing things organizing into some sort of linear MCS around DFW area (seeing some cells trying to initiate just north of there now also), and propagating south through ETX and toward Houston this morning (Friday) like the globals had been indicating the past days. Models are also insistent on some actual thunder cells (possible supercell or two) firing along the Rio Grande near Laredo overnite and moving east/northeast but that seems to be very conditional for tonight. Though I’m seeing one little thunder cell popping up not too far southwest of Brownsville right now also. There’ll likely be a significant outflow generated with N/ETX activity if it does organize and that would serve for renewed convective development later in the afternoon or evening closer to Del Rio - San Antonio - Houston area. Which still looks interesting for some severe potential into this evening. Then again Saturday and into STX also.

That 12Z Dallas/Fort Worth sounding has wet bulb zero (WBZ) height inside the large hail zone. But Effective shear at 36 Kts is much more meager for supercells than further north in OK at 67. BRN shear value at 40 is barely in the supercell range also.

The last time I had a similarly projected (severe) convective/MCS scenario happening around here in Southern TX in mid March (and at night) was back in 2016. Before that, on March 13, 2007. Even though the 2016 one had significant damaging winds in the region, I didn’t lose power. But the 2007 one I did. Though I don’t think the 2016 one had a Cutoff Low involved. 2016 one: https://www.weather.gov/crp/031816_highwind_hail https://www.spc.noaa.gov/exper/archive/event.php?date=20070313 The 2007 one had a non-severe (but restrengthened near coast) MCS, two nights prior and closer to sunrise. Tuesday evening March 13th, discrete supercells popped up around Laredo and Rio Grande plains area then gradually consolidated into a fairly linear but powerful MCS. Propagating east and came right through and off the mid TX coast, fully intact around midnight. I even got to see hail come down which is hard to come by here around the mid-lower TX coast. Very frequent lightning also of course. But there was more of a southwesterly 850mb flow and a thick stratus inversion deck in the low-levels that formed later that evening so I couldn’t see zip lightning out west outside until it got close. That very following morning behind the MCS on 14th (Wednesday), a few elevated supercells popped up near Victoria and headed toward Houston in the mid day.

SPC is likely going to expand that current D2 Slight Risk south-east going into tomorrow. GFS & Euro showing sufficient DL & effective shear around 50 Kts over southern half of TX Friday afternoon/evening (Del Rio - Houston line, south), with an unusually backed south-easterly 850mb flow happening right ahead of a slowing/stalling front. Because of a cutoff 500mb Low out west that’ll be edging a little closer by then with stronger shortwaves aloft in the SS obviously trailing in from it. But even through Friday night over STX, latest runs are showing CIN weakening more through the night with more storms popping up over the Rio Grande plains around Laredo overnite, going east. And with all that projected positive 850mb theta advection going on beneath steep ML lapse rates and sufficient shear, could still have some pretty powerful storms & supercells going on overnite into Saturday. Even if a little elevated. I see they also have a D3 marginal risk outlined over Laredo area toward San Antonio. But that’ll probably also be upgraded to a slight risk or at least in Deep STX if the front is still hanging around here until early Sunday. Can be earlier frontal push if mature MCS happens Saturday morning (which is good possibility seeing these things in the past around here). But this whole setup with a cutoff Low out west ahead a very modified warm sector in mid March (already 70F+ DPs on TX coast this morning), is unusual to say the least. There’s definitely going to be a lot of built-up instability that storms can tap into over southern half of TX (with enough lift), Friday afternoon/night.

Good multi early season MCS/MCC with lots-o-lightning potential (cutoff Low out west & projected steep mid-level lapse rates esp. on Euro), eastern to southern half Thursday nite - Sunday:

* Taken at 10am (regarding high-based cells in my previous post today). Could be another round later tonite - Wednesday.

Seeing a few high-based thunder cells popping up from an incoming ML shortwave across deep south since before sunrise this morning. BRO/CRP NWS offices did not forecast anything for today until they saw it now but already had somewhat steep ML lapse rates on Brownsville 0Z sounding yesterday evening. Already a good sign a more convectively active pattern is starting to return as later this week/weekend should be pretty fun with a parade of shortwaves coming in a more active southern stream. Potentially even part of next week seeing latest Euro runs as it got this morning’s sporadic high-based thunder activity around here right. Euro has been doing pretty well thunder-wise over TX since the beginning of the year. ‘Was not seeing very good reasoning with SPC’s D 4-8 severe risk highlights over the northeastern half (DFW region) as shear values were already projected to be modest there (consistently around 40 kts on both GFS & Euro the past couple days). And trending even more modest now on very latest runs on both models last night, for Thursday afternoon/evening. Though not too surprising on SPC’s part as they’ve been overforecasting the risks in the state lately. There may be a couple of supercells initially, but not seeing any kind of sustained/significant severe risk. Except for frequent lightning, smaller hail & heavier rainfall/flash flooding moreover. Might be a better severe risk in the southern half this weekend with higher shear values.

GFS, Euro, and all CAMs holding onto eroded sfc-based CIN over SETX midday - late afternoon today (Friday).- - - Wouldn’t hope for a dry spring too soon especially coming out of a fairly wet EN winter and active MJO pattern since the beginning of the year. GFS/Euro and their ensembles starting to latch onto a potentially more convectively active pattern later next week into next weekend over TX (and potentially through the early half of Spring). Looking at CFS longer range depictions also, it may not be useful in temp forecasting for a month out, but that is not necessarily the case regarding precip looking at its spring depictions since the past few years over TX. Keep in mind for later spring that May is typically spring MCS guarantee month also. Over the years, it rarely fails to have at least one or two good thunder systems impacting much of the state (especially eastern/southern half) during that month. MJO activity was relatively inactive the past weeks. But is also forecast to ramp up again out over the tropical Pacific in the coming weeks with a new activity wave progressing eastward. So that will likely have an impact on convective activity (potential severe) over the state due to enhanced subtropical jet influence as well in the coming weeks. The afternoon heat + orographically induced storms or discrete supercells out over the Mexican terrain (west of Laredo/Rio Grande) usually startup in March most years. The Euro is showing that could be happening mid-late next week as some more shortwave energy starts to come in from the west aloft in the southern stream, with hotter afternoon temps happening out there closer to or around 100 F on both GFS & Euro. - - - - - By the way, those bats you mentioned are called ‘Mexican free-tailed bats’ if I remember correctly. I do remember reading an article Austin/San Antonio NWS (as they’re very common in that region of TX) wrote about them back in the 2000s. Especially how they cause the donut-looking ground clutter depictions right around the radar site location on DFX & EWX radars like you referenced when the bats come out in huge numbers together at sunset during spring season. * Found detailed info on those bats: https://en.wikipedia.org/wiki/Mexican_free-tailed_bat

Been seeing some persistent thunder clustering (likely elevated, seeing tops no more than about 30 Kft on ET radar) going on around DFW the past couple hours. Things seem to be winding down for now, (especially with not much CAPE in place on 12 Z observed sounding this morning). But there was some pretty powerful CG strikes around the area on lightning data earlier this afternoon with this one being the strongest I saw on analysis:

12 Z runs yesterday and today on both GFS & Euro are starting to show a forecast trend in less convective CIN in S-SETX (including Houston area), Friday morning ahead of the initial Pacific front/dryline (dry, modest polar reinforcing front Friday night). But even though moisture, and DL shear is looking good (generally 60 kts) on both globals, forecast ML Lapse Rates aren’t (< 7) and seems to be trending lower. CAPE modest also (but sufficient). So that’s likely going to tamper atmospheric instability and severe hail, lightning threat a bit if storms happen. SRH values aren’t great also. Timing of frontal passage and 700 MB Low track over the TX Panhandle on those 12 Z runs comparison seems to be slowing down a little too. That could allow for a little better dynamics aloft. And instability on Friday in the lower levels and surface if frontal passage is indeed later midday. Will be interesting to see what CAMs (especially HRRR & ARW-2 as those have been doing the best lately), show when the time period comes into window tomorrow night. But since it is a positive-tilt (but formidable) incoming mid-upper trough being shown, I still wouldn’t be surprised if timing of shortwave energy ends up being somewhat out of sync with frontal passage in SETX. Though that’s usually a bigger problem with fronts further southwest in STX even if environment is favorable for storms. Especially this time of year.

I’ve seen those weird flat-looking kind of hailstones with cratered edges before. They’ve got that foggy white nuclei, so they were indeed supercooled higher up in those storms with more updraft strength.

How long did all the hail last?

The more recent CFS runs seem to be hinting at that for late March cold snap in the Central US also. Time will tell in the weeks after March begins. But I’m just not convinced winter is actually done. Even down here in TX. Especially if the -AO phase verifies and has longer duration or more pronounced.

Nice. Though I might question if it’s actually real (though I see the timestamp in the stream). But if it’s legit, definitely supercooled hail stones (foggy or white nuclei). I’m assuming the “cracked” area on top happened when it hit the ground before it was picked up. It kind of looks like the shaved ice that’s made or packed for snow cones. I wonder if anyone on here has seen spiked hail stones. I saw that in real life from my own eyes once back in May 2005 from an HP supercell that was about 2” diameter and picked it up. The hailstone was almost literally ‘spiked’ that it could make your hand or fingers bleed if you weren’t careful handling it, basically.

Evidently seeing more multicellular clustering on radar like the low BRN shear values on the late afternoon DVN & ILX soundings were indicating (rather than truly discrete supercells). I’m sure this will have a somewhat negative impact on tornado production in the risk area unless things get more discrete. - - - - - I’ve seen that a handful of times before on lightning data or radar over the years. It probably is a “false” lightning strike. But what it likely really means is that the atmosphere is electrically charged (favorable for lightning production) in that area when you see that and nothing on precip radar.

Number of multicell clusters literally exploded just in the past 30 minutes, just east/south of Davenport IA area. Couple of severe thunderstorm, and tornado warnings now also.

Not surprised as I just checked the SPC 22Z DVN (Davenport IA) observed sounding. Again similar to a few weeks ago in eastern TX, Low CAPE (282 MU), but both steep low & mid-level lapse rates. Surface temp at 72 F which I guess pretty warm for this time of year up there. WBZ height isn’t ideal for large hail, but FZL height is definitely low for more hail production. PW only at 0.57 BRN shear parameter is low at 24 which doesn’t support supercells though at least in the immediate Davenport area (mainly multicells). Gonna try to watch how this evolves as that environment aloft around there is definitely still interesting. *Edit: 22 Z or utc DVN sounding. ILX sounding just off to the southeast in central IL showing much more CAPE around 1000 & better shear parameters.

By the way, I’m assuming that was a typo for ‘South Padre Island’. But the way you wrote it is legit pretty much what it is anyway there in deep STX lol

Just to reference for everyone on here in case some aren’t as informed, NWS defines ‘Elevated Convection’ on their meteorological discussion glossary as this: https://forecast.weather.gov/glossary.php - - - And I never wrote that ‘elevated’ and ‘high-based’ storms were indeed the same and I already explained what high-based normally, or better yet, logically means. ’High-based’ though, can be interpreted differently because it is not an existing term in the NWS glossary. But, SPC also uses both terms in their convective discussions (and it’s been like that for a lot of years now as I’ve seen & read). Each forecaster may very well have a different interpretation of what's actually ‘High-based’ to them. But they could also just be meaning ‘Elevated’ at the same time too because there doesn’t seem to be an actual top layer criteria that strictly defines an elevated storm, looking at that NWS definition. ’Surface-based’ is indeed in their glossary as well. But it obviously has no room for individual interpretation because it inevitably means storms that are based within the surface layer (very near the ground), as written on there.

Well it seems that even very elevated storms rooted close to 700 MB, but especially, storms in majorly lower than normal CAPE environments are producing more severe/larger hail instances & lightning than before. Those baseball diameter hail reports around Tyler, TX that happened just a few weeks ago on the early morning right around sunrise of Feb. 11 (despite the favorable hail-producing environment aloft with quite cold mid-level temps this far south just below -15 C, steep mid-level LRs, and favorable shear parameters), was awfully interesting to say the least. Looking at the 12 Z FWD & SHV (Dallas and Shreveport LA) observed soundings ahead of a front, there was essentially no CAPE whatsoever in that area (including MU). I posted that info/data about it in the 2024 Texas discussion thread: https://www.americanwx.com/bb/topic/59912-texas-2024-discussionobservations/?do=findComment&comment=7228417 There was also 3.00” diameter hail reported from a fully discrete supercell between the I-10 corridor that runs from San Antonio - Houston TX on Jan. 8 (this year) also. But the environment in the area that day did have some actual CAPE on 12 Z observed SPC soundings (a little surface-based probably too) as it happened in the early afternoon. But even then, to have that kind of hail going on in early January is very unusual down around here close to the Gulf coast (looked at historical data also). As that’s normally only severe season type hail in spring. There was also a confirmed tornado report in an embedded, elevated (but likely near sfc-based) supercell in Brazoria county (near Houston TX) that happened in the very early morning near sunrise around 6:00 am last month on Jan. 5 that was also in a very low CAPE (< 500 j/kg) environment. Even though it was influenced by a warm frontal zone nearing the coast with favorable shear profiles and lapse rates aloft. The elevated storms also had a good amount of CG lightning going on that developed around TX coast when I was looking at lightning data early that morning and in another, weaker storm that developed near me. - - - Personally, looking at all those severe events I wrote above that happened this month and last month so early in the year is quite concerning to me. Especially when normal severe season this year starts next month.

That depends on what you’re meaning when you say, ‘high-based’. It usually means a step above ‘elevated’. High-based cells usually means that they’re rooted well aloft in the mid-levels above 700 MB (10 Kft above sea level), typically because the low-levels below that or the boundary layer all the way to the surface is too dry and/or stable. So obviously, the severe risk would be low because the depth of the storm is much shallower, if it’s actually high-based. Elevated thunderstorms usually means they’re rooted below that in the boundary layer or below 700 MB. Where they typically still have better access to more substantial warm/moist inflow (despite not being surface-based), in the appropriate environment. Usually in shallow polar/arctic frontal air masses rooted in the surface layer no more than a few thousand feet above the surface (basically a cold dome with warmer air overrunning it causing cloudiness down here in the south). So in that kind of scenario, the severe risk would obviously be higher.

Normally the risk of all severe hazards is virtually non-existent in very elevated or high-based storms.

Looking back on observed soundings at what happened in Eastern TX a few weeks ago early morning of Feb 11, larger hail, especially in discrete supercells seems to really hinge on wet bulb zero height (WBZ) being in the sweet spot between 7500 - 10000 on soundings. From NWS Glossary: https://forecast.weather.gov/glossary.php * FZL, cold mid-level temps & steep LRs should be no problem this far north in this topic’s forum region or risk area. Especially being early in the season.

Looks like Laredo is going to reach & potentially exceed its first 100 F mark of 2024 tomorrow (before end of February), looking at those latest GFS/Euro runs today. And seeing the actual high of 98 F today (even mid 90s in DFW) out there with all this ridging/subtropical high influence that’s been going on aloft since earlier last week. It’s not extremely unusual on record in February for Laredo to reach 100 F, but there may be a 50+ degree difference further behind Wednesday’s incoming Polar or Canadian front, on Thursday. Overrunning precip activity in the state late this week not looking impressive on models, but both GFS/Euro showing mid-level LRs will be steep Thursday night with rising PW ahead of some incoming mid-upper level southern stream shortwave energy. So can’t rule some thunder activity over the southern half/coastal region. But any severe storms with the front itself entering the state Tuesday night should stay east/northeast, this time. But, things could get more convectively active again with more severe potential starting early next week as it looks like the more active subtropical jet pattern from Jan - early Feb looks to be coming back at least to an extent in March. Polar air mass intrusions aren’t really uncommon in the whole state during March and even somewhat in April, at least during the past 2 decades. I also recall the 2007 Easter weekend cold snap (which was more unusual as it got into the 30s in STX that Saturday night going into Easter Sunday). There was another notable one in 2004 Easter weekend and it was interesting both had decent elevated thunder events down here at night going into Easter Sunday. Though I can definitely recall a number of March cold snaps during the 2010s. But most notably in 2014 (March 3rd to be exact), where that was an actual Arctic origin airmass that came into the whole state. It only managed around 40 F during daytime down here in STX (and solid overrunning low-level cloudiness), so the airmass was obviously very shallow. Though I do remember looking at the 0Z March 4, 2014 BRO & CRP observed soundings. Not only that and even more interesting and awesome this time, there were actual (still elevated) thunderstorms (some fairly strong near the lower Rio Grande on VIL) going on around here in the abnormally cold overrunning environment. And north-northeast from San Antonio - SE/ETX (all sub-severe in the state as far as I can remember even though SPC was monitoring when they got going in the state that evening). As a stout mid-level southern stream shortwave was coming in from Mex. It was definitely cold enough aloft in ETX for all winter precip types (thunder sleet/graupel, snow, and freezing rain). But seeing actual CG lightning bolts going on a couple miles just behind my backyard and 38 F actual temp outside down here…, man that was just crazy awesome. There was also ample MUCAPE with that activity back then (around 1000 j/kg), to note as well. Not like these Low/very low CAPE severe events that have been happening in the state recently earlier this month and in January. Which could be concerning going into spring this year. - - - - - Here’s a snapshot of the archived mesoscale discussion SPC had put up for freezing rain that evening back in March 2014:

It’s been basically like that for about a week now (closer to 2 weeks of above normal temps this time of year) down here in southern TX with more unusual mid-upper level subtropical high influence nearby in Mexico. But I’m glad winter isn’t necessarily over yet for the Southern Plains into March (possibly even into late March/early April looking at recent CFS runs especially if -AO phase does indeed return), as another polar airmass intrusion all the way south to the Western Gulf is likely after tomorrow. Despite the cooling effects will only last for about 3 days down here (which is typical).