3/3 FCST: Wednesday - A system to watch closely

Gene Rhoden

We may well have our first decent storm system of the approaching season come wednesday of this week. The current system obviously had problems from the get-go .....no surprise there when following the last system so closely. No moisture and forcing that was way to strong.

This system on Wednesday-ish looks like it promises to bring decent moisture ashore as trajectories off of the GOM appear to originate deeper into the western Carribean and have a rather long fetch over the western Gulf. We may have deep quality moisture surging northward on Tuesday with dewpoints in the 60s ....might even see a 70 or two in Texas. So couple that with rather decent lapse rates and good shear and we may have our first chase of the season .....maybe in NW Texas or the Red River Valley area. Time to charge the batteries? What is your take?

Been watching this myself since I'm coming out for the NSSL workshop. Since I don't trust anything that GFS says (think that particular model is a bit too aggressive, or at least I've found it to be so for systems on this side of the Mississippi), I'm waiting for a bit closer in to get ETAs take on it.
The last I looked, the surface low coming out of the 4 Corners along with east surface winds in central OK, 500 mb speeds of about 50 knots out of the southwest, dewpoints in the 50s, all pointing to possible development along the I-35 corridor (this was Friday night, so I may be totally outdated here). I'm concerned about the forecast for precip on Tuesday, so wondering if lingering cloud cover may be a major limiting factor. I'm also getting a gut feeling this may be an overnight event. (I tend to not chase at night, but I could be convinced to go out).
Definitely worth keeping an eye on (and bringing a bit of chase gear out for :) )!

I agree. One of the reasons I chose to stay home today (besides the obvious) was to save my guns for later next week. I haven't begun to really look at this sytem yet, but I imagine tonight will see my first attempts to try and figure it out. I'm not a big modelhead.......I get disappointed enough by the weather without creating more for myself by clinging to empty promises made by multi-colored graphics, lol.

But anyway, I'm getting kinda excited thinking about next week. My vidcam has been calling to me "Dude, take me chasing, take me chasing...."
I just about lost it when I looked at the 84 hour eta on this last night. For 12Z Wed, 3-3: Td's of 55 to near Snyder TX, vast moisture return continuing (as you point out, Gene) upper level support, dryline on TX/NM line, etc. etc......but what really blew me away was CAPE value of 1700+ in W TX.



In early March.

Still, there's something weird looking about it. I can't put my finger on it, exactly, but all the progged precip up in NE OK up into NE, I don't know....just something weird about it.

I am currently massaging my computer to get it to hurry up and bring me the latest eta run.

I won't be looking at anything very much until the day before this system - I don't like having my hopes dashed.

However I'll be watching forecast initiation times closely if we are considering Wednesday as a chase day - I finish work at 4pm which will be squeezing it a little.

For me there really was no question of going after the system in Texas on 2/28. I kept my butt at work - earning money so I can chase when it'll mean more to me - like May.

Looks to me like my target may well be within a triangle of Big Spring/Abilene/San Angelo.

Within this area at 00Z 040304:
sfc winds: ESE @ 5kts (hmmm)
sfc T: 70
sfc Td: 60
CAPE 2000-2500
LI: -6
Helicity: 200
850mb wind: SSE/SE @ 10-15 kts (hmmm)
700mb T: 3C
700mb wind: SSW @ 25-35kts (workable?)
500mb wind: SSW @ 60-80kts
300mb: Right front quad (not good)
500mb vert motion negligible or possibly slight subsidence for the target
700mb vert motion indicated a little west of target, essentially MAF

Not perfect, but very interesting.

I plan on hopefully chasing tomorrow!!Snow March 3rd???

March 3rd could be a snowy day for Iowa!!
First off... LOL Craig I think you posted to the wrong thread...

Secondly, and on topic...
I think it's important to realize that the CAPE forecast for WEdnesday afternoon from the ETA across the Red River Valley area are quite meager because the ETA blow up an area of rain / convection from northern TX into OK. This has an affect on sfc temperatures and mixes the atmosphere, which alleviates much of the instability higher up...

At any rate, I was more impressed with the setup when looking at last nights ETA... At the sfc, it seems that the sfc warm front sets up from east of San Angelo to near Texarkana / south of FSM by 0z Thurs. A large area of convection occurs along and north of this boundary through the day. As Gene and others have mentioned, Tds >60 will characterize the warm sector. This looks pretty nice at the surface...

The wind field, however, leaves something to be desired. The main 850mb jet/strongest winds is/are in eastern TX, with anything west of I35 in pretty meager flow. There is VERY good directional shear, however. The positive tilt of the upper trough (though it's a cutoff low at 500) probably will not help much either. It's interesting that the warm front position is quite different than it was from last nights run (which only went to 12z Wed), which had the w/f along the Red River Valley...

I certainly do agree that this is something to watch. It's important to remember that we are still 'pre-season' for the most part, although it time for TX to begin the uptick in severe weather potential...

I just looked at the 12z GFS, which I hope verifies moreso than the ETA. On the GFS, the warm front is along the Red River, with the dryline/inverted trough stretching from maybe Vernon ,TX, southward to the low in far northern Mexico... Again, however, the 850 wind max is more near the TX/OK/AR/LA area, well east of the dryline. The low then lifts rapidly northeast across FSM and into IL by Thursday afternoon. Something to watch still...

The ETA brings what appears to be a shallow cold front across the Red River Tuesday morning (or lays a warm front there, depending on how you look at it), and with northeast surface winds settling in behind it while the LLJ cranks up, I suspect we'll be dealing with lots of isentropic lift. So, precip out the yin yang before our upper level energy arrives, especially if the dewpoint forecast verifies. Looks like more of a rain-producer than a severe weather producer.

I could see things possibly getting interesting on the Edwards Plateau, however, where surface conditions may just be more favorable for organized severe weather. That's pretty typical of early March.

Worth keeping an eye on, though.
I have to agree that the system for Wed-Fri looks very interesting. The latest UKMET/ECMWF are actually a bit stronger than the latest 12Z/18Z GFS. Models agree that a strong 500mb vort will dive south into Mexico on Wed, then eject out into the Plains on Thu. This will result in a sfc low developing somewhere in the TX/OK vacinity. Using the GFS, the low then tracks towards Chicago deepening to ~985MB (the ECMWF deepens it to 980MB, with a similar track). Since the event is still far away, I usually just look at the synoptic setup, and leave instability out of the picture. Looking at the sfc low track and upper level wind fields, it looks like the threat region is from the southern Plains northeast into the Ohio Valley, with the OH Valley/northern TN Valley having the biggest threat come Thu into Fri.

I have also noted something rather interesting...Take a look at the 12Z GFS at 102HRS, then go to http://www.weathergraphics.com/sfcupr/ and check out the analysis for April 3 1974. The SFC and 500mb patterns are similar (particularly the 500mb level). Just and interesting climatology note.

I'm looking at the ETA 72 and 84 hour progs and just notified work that I will be taking WEDNESDAY, MARCH 3rd off work. So far the postives are: 1) surface moisture returns with 60+ dewpoints in central Texas (yeah!), 2) tremendous high amplitude wave comes through the west with 100+ knot jet aloft, 3) timing looks good for upper wave to coincide with maximum daytime heating, 4) surface warm front across north Texas will back winds along the Red River to easterly, 5) nice diffluent area showing up in upper jets. So, what is wrong with this system? Well for one thing, the upper dynamics are very powerful and can shear out the storms. We really need the instability at the surface. Another thing is that this system is digging way south, so Oklahoma looks shut out of it. If it digs any more, we'll be chasing in San Antonio! Right now, I'm looking at a Brady - Throckmorton line. Other factors to consider are cloudiness and the cap. On the up side - it is a tornado outbreak and the DFW metroplex could be in trouble. On the down side - just another squall line with tail end charlie south of Del Rio. This situation bears watching. Now back to the Oscars... TM
If the GFS turns out to be correct, I like both Wednesday and Thursday. Actually, to my feeble mind, Thursday looks better, although it will be over a less chaser friendly area.

On the other hand, the ETA seems to position the low much farther S at the beginning of the period. Therefore until the days in question get closer, I think I'll hold off on any predictions. But it's certainly worth watching, as it could be a pretty significant two day event if things fall into the right places. At least we have something to look forward to besides cold temps and snow for a change!


John, discrete storms as opposed to a mesoscale convective system (squall line).

As far as Wednesday is concerned, I believe that supercells will certainly be possible, as long as the storms can remain fairly isolated. ETA has CAPE up to 2500 j/kg in western N. Texas, and at least 200 m2/s2 helicity in the same region. Local backing of the winds within the vicinity of the warm front could enhance the tornado threat of any storm that rides the boundary.

My main concern with this system is the lack of strong 850 mb winds where the greatest instability is located. If these were juxtaposed, I believe the tornado threat would be greater. As of the 12Z ETA run, the greatest CAPE will be located in the Abilene with 850 mb winds region wide less than 30 kts. However, a LLJ max of 37 kts is forecast by the ETA in central Texas and it is collocated with the boundary and some very juicy dewpoints (near 65 F).

All in all, this looks to be a legitimate chase day for those who can make it down to central/north central Texas.

First off, I'd have to say that there are some pretty major differences between last nights 0z run and the latest 12z run from the ETA. The upper trough is about 150 miles farther west by 6z Thurs (western NM instead of central NM), and is more positively tilted. On the other hand, there is significantly less rainfall (qpf) north of the warm front. Actually, with the trough being farther west, the sfc low is also a little farther west. This, along with the lesser amounts of qpf north of the boundary, has seemingly allow the warm front to move farther north by 0z thurs (Weds. evening), and has allowed the untable air (with CAPE >2000), to move into northern TX.

I do hold the same concern as Gabe... 850mb winds are farther east, for the most part. However, this seemed relatively common last year (strongest 850 winds well east of the dryline)... What is of more concern to me is the tendency for the ETA to shoot the low/trough out of the SW US too quickly. This has been in play the last couple of runs, as the systems has slowed down each run. Well, the system doesn't slow down, per-se, but the forecast position of the system slows down ;) . At any rate, if this trend continues, we may run into a signficant timing issue, and evererything may pass through the area durng the night Weds and morning Thurs...

In all, each run seems to be getting sweeter, so we'll just have to see...
Indeed. The morning models slow down this system. This will allow even more low-level moisture to advect northward. The 12z ETA now has 60 dewpoints all the way to Oklahoma City by Wednesday evening! The warm front still remains across north-central Texas. Yes, Wednesday is looking more and more like the day before the dynamics spill onto the plains. I agree with the concerns others have expressed over prior convection and the cap, and it now looks like the system is about 12 hours out-of-phase. But, Wednesday looks like the first chase day of the spring for me. Looking at the Junction-Abilene line right now. TM
There's certainly no question this storm has WAY more moisture to work with. It will be interesting to see how things come together with this system.
The main concerns I'm focused on for Wednesday are a possible cirrus deck, and a lack of upper level support. Based on current water vapor imagery and backed up by the ETA, it appears there may be cirrus worries for Wednesday.

If there is no cirrus deck, then Wednesday will be a great chase day. If a cirrus deck prevails, this will keep surface temps down, and I'd then be worried about initiation. The current 850 temp forecast shouldn't be a problem, ~15C, but it could be with cirrus.

Otherwise, Wednesday looks great!

Jim Bishop
Today's nice weather is having the usual effect, getting me excited about the coming setup despite previous concerns. The 12Z ETA isn't helping, either.

It now looks as if the warm front will prove more of an advantage than disadvantage, giving us a good boundary to work with in North Central TX. One of the biggest concerns I have is convective debris from storms Tuesday night limiting insolation for Wednesday. On the other hand, any storms Tuesday night might make for some outflow boundaries to work with. Dependant on what happens, it could be a tricky situation at the surface Wednesday morning.

I'm feeling more confident now that North Central TX will see some severe weather out of this system, but I'm not sure yet what my chase strategy would be Wednesday. Obviously, the warm front will be the primary player, but with storms potentially all over the place, picking a target is going to be tough. To be honest, I usually don't like to chase days when there are numerous clusters of storms in the muck, as your success really comes down to simply being in the right place at the right time. April 7, 2002 comes to mind...lots of decent storms that day, but only one that interacted with the warm front at just the right time and place to produce a significant tornado.

I'm getting in the mood to chase, but I'm not clearing my schedule for Wednesday quite yet. I want to see what transpires tomorrow (and especially tomorrow night, which could be interesting in itself).
I've been looking at everything and I agree that there is some promise.

However, I do have a question about helicity and the models. I'm not like reliant on the models or anything, but the forecast helicity in the North/Northwest Central Texas area is, like, 50 m^-2 s^-2. Don't you need higher values in order to even get weak tornados? How important is the helicity forecase relevant to everything else, and how good is the ETA for forecasting helicity anyway (in your experience)?

I always feel stupid asking questions... :oops:

Storm-Relative helicity is VERY dependent upon storm motion. While 50m2/s2 is weak in many regards, one must ask with which motion is this the result of? In other words, a storm moving northeast at 55mph may experience helicity of 50m2/s2, while a storm in the same environment, but moving east-southeast at 40mph may experience MUCH more. In cases of supercells, motion tends to be slower and to the right of the mean mid-level wind, which tends throw any model forecast helicity out the window...

I find that it is difficult to put much weight on model forecast SR helicity (make sure it is SR, too, and not environmental helicity, which negates storm motion). Oftentimes, the storm modifies the environment itself, or at least the environment is modified by mesoscale features that can hide in coarse model grids and go undetected by the models. Just something to keep in mind...

Jeff Snyder
Well, the 0z models are starting to roll in... Just from the 0z graphics, it doesn't look too good (well, as good as earlier runs at least). CAPE is meager (<800) across much of north Texas and points northward. Now, I think much of this has to do with the fact that the ETA convects across the area by 0z, and thus decreases surface temps and related instability at that time. This explains why there isn't progged to be much more CAPE across the area at 0z than 18z. So, I don't think I'd take the 0z CAPE too stringently.

Again, as has been the case, the system continues to slow down. The problem is, by the time the system kicks out on Thursday, upper forcing is very strong and will likely result in a strongly-forced squall line...

I think the best convection will likely be nearer San Angelo than SPS, I think, mainly because of instability reasons...

Any other thoughts?

I second that Jeff. After looking at the 0Z Eta & GFS, certainly looks like the best chance of any solid convection & discrete storms is going to be in the SJT CWA. But with the 850 flow backing significantly NW of the upper level low (not sure how much I believ that, but there has been some run-to-run consistently), 0-1km SREH may be limited at initation time in the SJT CWA.

The Gulf is defintley open for business again though. High precip totals nonetheless for N. Texas/S. Oklahoma (0Z Eta has returned 60°F+ Dwps across the Red River) but it appears the severe potential will be limited thermodynamically north of I-20.
I'm not too impressed with the chances for along the Red River at all... north of the warm front there is little instability... probably a lot of left over clouds from the previous day (elevated stuff?)...

Maybe in and around Junction and South.... that area of Texas. Better instability... decent shear, but both the AVN and ETA showing some mid level moisture getting pulled up from the Pacific... above a dry punch at ~700mb. I'd be concerned about mid-level clouds perhaps?

Laptop is still 2500 miles from here, won't have it for over a week. Perhaps the funds could better be saved for May/June. I'd be looking at a 6 hour drive from the Sun City, on a 3-day stretch off work, but right after an 3-12 shift. Intrigued, though I'll probably sit this out.