Stx_Thunder

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).

CPC wrote an interesting and uncertain Week 3 - 4 forecast discussion just this past Friday mentioning about a potential SSW: https://www.cpc.ncep.noaa.gov/products/predictions/WK34/ I haven’t read enough into (Sudden) Stratospheric Warming phenomenon and particularly data yet, but what are the odds of this happening, going into or in March? If my memory serves me right over the past few years, I’m sure it’s also had a significant impact on the AO going back into or staying in a Negative phase longer. Which could keep winter from ending too soon over the Central US.

Apparently baseball size hail (2.75 in. diameter) was reported a little further southwest of Tyler on superbowl Sunday morning: It turned out to be more severe wx active than I thought it was going to be in ETX. Especially being early in the morning. I was a little under the weather, so I wasn’t aware of how potent the environment aloft actually was for large hail. But I definitely see why it happened around there (despite the very limited CAPE in the region), looking at the 12 Z DFW/Fort Worth sounding from that morning: - I circled the parameters of note. But particularly the FZL (freezing level), and WBZ (wet-bulb zero height) ones were definitely both in that SIG hail range. WBZ height wasn’t any higher further east/southeast on SHV & LCH soundings (Shreveport & Lake Charles LA). But anything between 7000’ - 10500’ means a heightened large hail risk. Also have to note that fairly impressive BRN (Bulk Richardson number) shear value @ 200 concerning supercell risk. (from NWS glossary: https://forecast.weather.gov/glossary.php) * Shreveport LA observed sounding: - Pretty deep, well-defined 500Mb Low out west over NM on 12Z observed sounding compiled data that morning also.

Interesting overrunning deep convective scenario there in MO. A very good amount of strikes recorded on lightning data today progressing east through much of the southern half of the state. I’m sure graupel and a little hail was also falling in some of the stronger storms as 700Mb (10 Kft) temps were already below 0 C this morning, and 500Mb (18 Kft) around - 20 C. Which is quite cold aloft in the mid levels for such deep convective scenario in the south. And the residual chilly airmass earlier today was extremely shallow with an E on the 12Z SGF (Springfield MO) upper-air sounding this morning. Mid-level lapse rates were fairly steep too (7 C/km). Which was also causing the substantial lightning activity.

Big 850Mb cap amazingly weakened to literally almost nothing down here early this morning between 0Z yesterday evening's and this morning's 12Z CRP sounding ahead of that final, main convective line with the frontal boundary. So I actually managed to cash in on it down here. Didn't last long as it was pretty thin, but was decent with fairly frequent lightning (especially with such shallow convective tops on radar no more than about 30 Kft). Already looking forward to next round of thunder events soon lol, as that alone was a good sign in this unusually active pattern of late - But it is still looking very convectively interesting going the week of Feb 12th. Even into Feb 19th the following week. GFS/Euro & ensembles still holding onto a very unusually persistent troughing pattern for this time of year setting up out west next week of Feb 12th (at least within the active subtropical jet staying parked over northern Mexico, into TX). GFS in particular showing basically round after round of activity moving through the southern half of state during that week. SPC was also already mentioning severe potential for next weekend as well in D 4-8 outlook, earlier today (Saturday).

- Main thunder line developing west of San Antonio. Latest 6Z HRRR and 0Z FV3 both showing it slicing through mid-upper coast (CRP - HOU) before sunrise. Can also clearly see that developing mid-upper level Low up there off to the west of Amarillo/southeast NM/CO border.

Incoming mid-upper trough into Plains is indeed a bit negatively-tilted (looking at that backed south-southeasterly flow up there in that region) on observed 0Z 500Mb & 300Mb data this evening. That could also be because of that Omega block High that's off to the northeast near the Great Lakes region now. 500Mb Heights are now < 570 in most of TX. And we're pretty much getting into the LFQ down here of that pretty strong ULL jet streak nosing in from the west. So can't rule out some persistent stronger storms through the rest of the night at least over the southern half of state. The clusters in San Antonio region have a good chance of sustaining themselves/becoming more organized toward Houston with all the SSE inflow going on now around there too on HGX radar VWP in the lower levels this evening. And mid-level LRs are quite steep on 0Z CRP sounding (> 8 C/km between 700Mb & 500Mb) too, but.. there's that typical stout cap/EML just above 850Mb down here (though it's below 850Mb on BRO). So thunder action again doesn't look too great here in STX because of that & the incoming front tonight as there'll likely be more high-based cells like the CAMs were showing since yesterday.