03/08/2006 DISC: TX/OK

[Bill Tabor]

I don't see any torns logged at SPC. Looked liked one of those cells in north Tx or southern Ok might have produced. Does anyone know?

Also congrats Evan on your first chase!

Mickey, Shane, and the rest of you. That's the way it goes - it's March. Those curses just go away when the storms start producing. You just need the right setup / system; otherwise as you know it can be a lot of work (albeit still fun usually).

 

[Jeff Snyder]

One of the SWS (or maybe it was a warning...) from OUN mentionedthat law enforcement reported a tornado down in Love county, but I haven't seen an LSR for that yet. I'm not sure if that just slipped through, or if the report seemed a bit sketchy and they want to verify it first.

In the end, I think there just wasn't enough instability for the massive deeplayer shear in place yesterday. We watched a couple towers go up and get sheared to shreds. There was that relatively persistent area of light precip that ran SW-NE from western n TX into sc OK and ne from there. I'm not sure what caused that, but it seemed as though almost all convection fired in that mess. Radar velocities showed quite a few anticyclonic couplets, which, knowing that there was some backing with height near 700mb during the mid-late afternoon, may indicate that the convection was largely elevated, with updraft parcel levels near that area of backing winds. There were a few areas of >4 Supercell Composite Parameter (Left-mover) in north Texas, so the RUC was analyzing the area to be favorable for anticyclonic rotation. The cirrostratus deck was hard to deal with, as it shut off the insolation and may have helped keep the area capped to surface-based convection. By 9-10pm, however, large-scale ascent ahead of the vort max, and perhaps mechanical mixing from the very strong low-level jet, helped remove the cap and destabilized n TX enough to support sfc-based convection.

 

[Scott Olson]

I wouldn't be to suprised if the Clay County Supercell produced a tornado. For seven or eight scans that cell was showing several couplets, including one that would have been definately rain-wrapped. Makes me tend to believe the Law enforcement report of a tornado in Love County. Of course if no one can see it (night) and no one notices damage there is nothing to go on.

 

[Sara Johnson]

I'm sure they're still assessing things, but it looks like no tornado reports. Curious as to what may happen today.

Nice cloud structure pics, guys!

 

[nickgrillo]

I would... SPC mesoanalysis was showing ridiculous SBCIN and MLCIN (>200j/kg) all over the moist sector yesterday night, with the increase of CIN owed to diabatic cooling. For that matter, I think the majority of yesterday's convection was elevated, and were largely hail producers (with both large CAPE and large SRH contributing to updraft rotation in many of the storms, but rooted above the inversion layer).

Here is a couple SBCAPE / SBCIN and MLCAPE / MLCIN graphic from SPC mesoanalysis at the time of the Clay County, TX supercell (around the time of the tornado report):

<img src=http://midwestchase.com/2006/sbcp-3-8-2006.gif>
<img src=http://midwestchase.com/2006/mlcp-3-8-2005.gif>

That is very large low-level negative buoyancy. Now, at the time -- very strong low-level shear was also present, and with a large amount accumulating within the lowest 1 km layer, although about >500m2/s2 0-3km SRH was invof supercell, per SPC mesoanalysis -- contributed to the significant updraft rotation. However, low-level CAPE (CAPE present within the lowest 3 km) was virtually non-existent in the inflow sector, except for a small blob (per SPC mesoanalysis) in southcentral/southwest OK at the time of the supercell -- and this, combined with the high LFC heights (>2500m) would lead me to believe the supercell was rooted above the deep-layer of CIN -- thus, dramatically reducing any tornadic potential with the storm (or any of the other deep convection around the area).

The storm initiated and matured in an area with very large low-level negative buoyancy and relatively moderate CAPE (with the majority, if not all of the positive energy rooted above the lowest 3 km) so I would have to say the tornado report is quite possibly false, since the storm was rooted above the layer of large CIN and was very likely elevated.

Originally posted by Scott Olson
I wouldn't be to suprised if the Clay County Supercell produced a tornado. For seven or eight scans that cell was showing several couplets, including one that would have been definately rain-wrapped. Makes me tend to believe the Law enforcement report of a tornado.

 

[Jeff Snyder]

Nick,

Possibly, but I'm not sure we'd see 70-75dbz echoes with an elevated storm. I'm a little suspicious of those mesoanalysis graphics... At the time of the 0z FWD sounding, the DFW airport reported 73/57 while the sounding indicated almost a relatively weak cap (40j/kg cinh). By 10pm, DFW was 70/60 -- the temp dropped, but the td rose, so theta-e may not have dropped any. Since the winds stayed up, temps didn't really cool off much after sunset, and it doesn't appear as though the boundary layer decoupled much. With strong ascent ahead of the wave to the west, I'm not sure how CINH could strengthen so much so quickly. So, the RUC shows massive CINH, but the environment didn't look a whole lot different than it did at 0z, when the FWD sounding showed only relatively weak cinh. Now, if the temp drops at the sfc at the base of a previously well-mixed boundary layer, you'd usually see a rapid rise in CINH for a surface parcel. In this case, however, the Td increased after dark, so the parcel would reach its LCL at a lower height, after which time it'd rise following a moist adiabat. Since the LFC was a ways above the LCL on the 0z sounding, a drop in the LCL (thereby 'starting' latent heat release ealier), the LFC may have decreased in time, so total CINH may not have increased as much the RUC indicates. In addition, if the supercell was able to initiate with surface parcels earlier in the evening, strong rotation of the mesocyclone would have developed strong vertical pressure perturbation gradients, which could have allowed the storm to ingest negatively buoyant low-level air (a similar reason, partly, why it can be much easier to sustain a supercell in a relatively capped environment than it is to develop a supercell in the same environment)... Vertical acceleration is a function of buoyancy and vertical perturb pressure gradients, so weak or even negative buoyancy may still occur in an intense updraft should the vert pert pressure grad be intense (i.e. strong rotation).

BTW, I'm not entirely arguing that it was sfc-based. I'm more thinking aloud than anything... I agree that the lowest few 100m may have been stable enough to prevent tornadogenesis. Then again, a strong updraft may contain strong enough inflow to allow for the mechanical mixing of the lowest few 100m of stable air, weakening the stability of the near-surface air.

 

[Mickey Ptak]

Re: 03/08/2006 DISC: So Were There Any Tornadoes Yesterday?

Originally posted by Bill Tabor
Mickey, Shane, and the rest of you. That's the way it goes - it's March. Those curses just go away when the storms start producing. You just need the right setup / system; otherwise as you know it can be a lot of work (albeit still fun usually).

I think we where all aware of the fact that it was March and the type of systems we normally have in this month. When it's close to home though I would rather take my chances chasing a marginal setup than sit in front of a computer and say I told you so. I'll take the hard chases with the easy chases. It builds character. Of course if you don’t want storms near your home just call Shane and I we’ll take care of that for you… As long as it is March.

The great thing about yesterday (and 3/7/06) was that it was really not hard to forecast the best target. Yesterday we had two places worth noting and IMO we picked the better of the two. That is just my IMO.

I will say this though the RUC really had a good grasp on this system. It forecasted the surface winds to back around 3-4pm along with the southern part of the DL retreating. It was really good with the timing of the jet max also.

Also the RUC forecasted the CAP to once again become moderately strong around 0Z. I think that verified completely thus the reason for the conclusion of all the initial storms that fired along the DL. There must have been some warming of the 850mb-700mb for them just to dissipate the way they had. I mean it was just one after another. Then again we had lost a lot of daytime heating due to the sun setting in that time frame.

BTW: I like this new DISC setup… It gives us room to analysis what happened and bounce suggestions and ideas off of each other.

Mick

 

[Scott Olson]

Nick, the soundings/mesoanaylsis seems to suggest that it would have been surface based but im not sure thats the case. The storm was present several hours before so it's possible the updraft convergence helped maintain it's current level. As well as strong vertical pressures as the mesocyclone intensified in 90kts of 0-6km shear. Jeff has already pointed out some of the very high echos in the lowest tilt (that would suggest it wasn't based above 3km). But also i'd like to point out the fact that the storm was being sampled somewhere in the 5,000ft range in the lowest tilt (about an hour prior to very strong rotation) and the storm exhibited a very strong inflow notch. That suggests to me that radar data has proven that the storm was based at least 1.75km or lower and that the strengthning vertical pressure and convergence would have easily kept it from becoming based higher. There wasn't certainly no shortage of low level SRH with 700 m2/s2 sampled nearby and 1k j/kg SBCAPE.

 

[nickgrillo]

The FWD sounding at 00z [using VTC] still showed ~50j/kg of SBCIN (and ~30j/kg of MLCIN) with virtually no (perhaps ~10j/kg of 3km CAPE) positive buoyancy located below the lowest 3 km. I'm not arguing that the storm didn't exhibit a strong, deep mesocyclone... I just think the rather significant near-surface stable layer could have prohibited tornadogenesis. There was plenty of deep-layered shear (>60 knots in the lowest 6 km) and low-level shear (>500m2/s2 0-3km SRH) to favor updraft rotation and induce dynamic vertical pressure gradient forces to help overcome stronger environmental CIN. However, diabatic cooling could have strengthened CIN greatly (with a >4F drop in surface temperature around FWD between 00 and 04z) in the four hours (between the time of the DFW sounding to the time of the tornado report) which could have rapidly limited tornado potential with the storms. There is really no way in saying how much environmental CIN can be overcome by dynamic vertical pressure gradient forces, but numerous recent studies have shown that with increasing ambient CIN -- tornado development drops off significantly.

I'm not definitely saying that the Clay County supercell wasn't surface based, but I'm also not saying it was. Perhaps I'll retrieve the 00z sounding from FWD and modify it.

 

[Glen Romine]

The idea that the DFW 00Z is even somewhat representative of the actual storm environment is questionable at best. Also, an established supercell with a low-level mesocyclone likely has a significant amount of surface parcel inflow even with CIN up to around 150 J/Kg. As you get much larger than that, it becomes less likely, but the SPC mesoanalyses are a blend of observations and a short (1 hr) forecast, so are error prone, and can smooth out meaningful localized features. You really would need to go back to the time of the report - look at nearby sfc obs to try and assess the sfc inflow properties, and then get a sounding appropriate for the environment the cell was in (which would likely require some educated manipulations). There were significant changes to the profile at DFW between 00Z and 06Z - so neither may be very representative.

Glen

 

[mikegeukes]

Nick is this one of the articles you are referring to:

Estimations of CIN and LFC Associated with Tornadic and Nontornadic Supercells
http://members.cox.net/jdavies1/waf796/waf796.htm

Mike

 

[David Drummond]

Originally posted by Jeff Snyder
One of the SWS (or maybe it was a warning...) from OUN mentionedthat law enforcement reported a tornado down in Love county, but I haven't seen an LSR for that yet. I'm not sure if that just slipped through, or if the report seemed a bit sketchy and they want to verify it first.

We saw one chaser out there we met up with south of Ardmore. He had some video of something from that area that was VERY suggestive of a funnel cloud/tornado. Just looking at the video I would say 95% it probably was. It was in the right place, at the right time, and supported by radar. If it was in fact a tornado, it was brief.

 

[nickgrillo]

Yeah...

Originally posted by mikegeukes
Nick is this one of the articles you are referring to:

Estimations of CIN and LFC Associated with Tornadic and Nontornadic Supercells
http://members.cox.net/jdavies1/waf796/waf796.htm

Mike

 

[mikegeukes]

Latest Local Storm Reports out of NWS OUN, does not list any tornadoes
http://www.srh.noaa.gov/productview.php?pi...ersion=0&max=51

Severe Weather Statement is where it mention the tornado
http://www.srh.noaa.gov/productview.php?pi...rsion=14&max=51

No Public Information Statements about the tornado either,

Mike

 

[Jason A.C. Brock]

I was listening to area storm spotters on the Clay County Texas storm but never heard of any confirmed tornado reports. I did notice the lack of spotters actually on this storm once it moved into Clay county. There were spotters on the cell from Throckmorton Texas to Roundtimber in extreme SE Baylor County to Megargel in extreme SW Archer County to Olney in Extreme NW Young county and then from Anarene and Windthorst in SC & West central Archer county. Once the cell moved towards Bluegrove area of Southern Clay county spotters dropped off. This tends to be the case in this area especially during nocturnal events.
I did hear of an actual spotter report of a tornado once it moved into Oklahoma just over the river. The cell also had two areas which were capable of producing a tornado according to NWS.
I wouldnt be surprised at all if the cell did produce a tornado in Clay county but I believe the lack or spotters made it really hard to determine. Of course if the storm produced during a rain wrapped stage and it being at night I could also see how it was missed.
Throckmorton had golfball size hail
Rountimber had dime size hail
Megargel had nickel size hail
Olney fire department reported baseball size hail and .02 inches rain
I Was hoping these cells would help out with rain but they were moving so fast and producing alot of hail. Megargel reported hail was covering the roads. No reports of rain over an inch anywhere except Noconna in Montague County from a strong cell earlier that produced 1.3 inches. This rain off quickly tho due to very hard dry ground and the short amount of time the rain fell in.
A resident did call in a possible funnel cloud between Roundtimber and Megargel but we all know how those can go. :?
It was a March situation s the lack of any tornadic activity isnt too mind boggling. I do see why a watch was warranted however. Better safe than sorry I say. Id rather be informed tornadoes could occur and they dont than to not be and they do. Of course some may disagree.