4/25/09 FCST: NE/KS/OK/TX

[Andrew Pritchard]

Let it be know that I'm opting to not chase Oklahoma tomorrow so you can discount this as "not chasing so he hates the setup" syndrome.

There is excellent curvature on the low levels, but note the speed at the mid-levels. It'd be nice to see a little improvement there or you'll not only end up with an after dark show, but an HP after dark show at that. I'm all for after dark chasing, but chasing HP's after dark is a different story.

Anyway, it's certainly worth taking a chance on, just something to consider.

 

[Alex Lamers]

I won't spend much time to restate what many have written in this thread in the past 12 hours. However, I will say that I think there is a conditional threat for strong to violent tornadoes after dark tomorrow across western Oklahoma.

+1

I agree, the forecast hodographs, when combined with the degree and depth of moisture, and the strong instability is a concerning combination. I'm interested to see the 4km runs from NSSL and SPC to see how they handle the latest trend of blowing up the dryline late in the afternoon.

If storms can manage to stay discrete, they could be a major concern 7-10PM timeframe. Anything that stays by itself should be very chaseable given manageable storm motions. Right movers will be moving at maybe 15 knots and that could be generous.

The latest NAM sunk a little south, but both it and the GFS support a tornado threat, just vary on the exact location. It seems like a good idea to head west on I-40 for now, and then see which model is right.

AJL

 

[Brian Stertz]

I am headed off to bed and will still target the Glazier-Canadian TX area as my head to place tomorrow morning. Will leave before dawn from KC and will be chasing with Rich & Ryan Thies. The hodographs all across W.Oklahoma are insane (strong LL shear...wide and curved hodographs)....couple that with good moisture and lowered LCL's after 00z, and there is potential there for some W. Oklahoma wedges. Good luck to those chasing.

 

[Connor McCrorey]

I just made my final forecast post on the blog, http://blog.texasstormchasers.com/?q=node/5. See yall out there!

 

[Adam Penney]

I will be heading out at 6:00 a.m. tomorrow morning from the KC metro for the Woodward,OK area. It seems to do a sufficient job of splitting the difference between the models and has many options to readjust.

Good luck to all out tomorrow!

 

[Mikey Gribble]

I really like the 00Z GFS and totally agree with the statement made by Alex and Jeff that strong tornadoes are a very real possibility. My initial target right now is Woodward and like other have mentioned we can adjust from there depending on where exactly everything sets up. If you haven't pulled up the forecast soundings for Woodward and the area northeast of there you ought too. The composite indices were surprisingly low and 5km and 10km SR winds are a little weak, but otherwise it is an excellent setup for cyclic tornadic supercells.

I will say my prayers that the GFS verifies tonight before bed. I firmly believe it portrays a slightly better tornado threat when compared to the NAM.

I posted a forecast and a map on my blog for anybody who is interested. Here is the link http://loadedgunchasing.com/blog1/

 

[Mike Peregrine]

Solid Theta-E convergence corridor setting up across the panhandle dipping over into western OK by 0z per WRF. Cap looks to be eroding by this time too. Brian's Canadian target looks pretty appealing ...

Edit - Mikey's right about the hodos around Woodward ... w o w

 

[Shane Adams]

Let it be know that I'm opting to not chase Oklahoma tomorrow so you can discount this as "not chasing so he hates the setup" syndrome.

There is excellent curvature on the low levels, but note the speed at the mid-levels. It'd be nice to see a little improvement there or you'll not only end up with an after dark show, but an HP after dark show at that. I'm all for after dark chasing, but chasing HP's after dark is a different story.

Anyway, it's certainly worth taking a chance on, just something to consider.

Actually 40kts at 500 with the type of CAPE we'll have tomorrow is quite conducive to classic type supercells. You don't need 70kts at h5 for classic supercells when you actually have instability.

I'm rather surprised some folks who had the chance balked at this one; nothing's come close so far in 2009 to this weekend's potential.

 

[John MacKay]

If I'm not too sick (felt horrible in the morning and afternoon past 2 days), I'll be leaving PHX at 7:20 AM MST, getting to Tulsa at 2 PM, then heading west to Clinton to check data (getting there by 5:30 PM, hopefully) before going west or north to the action.

The 4km WRF paints an interesting picture, breaking out some supercells around 6-7 PM time frame, then looking like monsters until a dominant one takes root. Those of you pegging Clinton and other parts of W. OK seem to be on to something. The unfortunate part is it looks HP, one of the concerns we might keep in mind tomorrow approaching these storms. Those channeling the US 83 corridor in E. TX panhandle (Canadian-Wheeler-Shamrock) seem to be in the best position to run along with these storms for their whole journey. Because of time, I likely can't get that far west without sacrificing intercepting position.

At least this is somewhere close to GFS model guidance, and now the NAM after the inconsistency earlier.

Good luck to those out there tomorrow. I hope to join you late for the show. If anyone is free to nowcast for me (Sat. and/or Sun.), feel free to PM me. I will get to you before or after my series of flights.

 

[Chris Nuttall]

Well, I had plenty of time to peruse the data at work today. Disclaimer: This post is based off the 18z NAM and 12z GFS, since the 00z runs were not in yet when I left.

The NAM is continuing to drop the cold front pretty far south into the TX Panhandle bringing the triple point fairly close to AMA. I've been treating the NAM as an outlier (although not totaling discounting it) since the GFS has been far more consistent run-to-run with itself and the ECMWF.

It appears a cap should hold things down for much of the day. I expect initiation to be somewhere around 23z-00z, so we should have a good 2-3 hour window of daylight to work with for spotting. Winds back dramatically near the triple point, so shear will definitely be maximized in that area, however surface winds are progged to be SE pretty much all along the dryline. Storm motion should not be too bad either...looks to be around 25-35 kts.

Dewpoints should be well into the 50s to near 60 in some places, especially further south, so moisture will not be a problem. There's also a chance that some convection could fire along the retreating dryline after the nocturnal LLJ develops. That could play some havoc with Sunday, however, that's a topic for another thread.

For Saturday, the key will be two-fold: (1) how far south the cold front makes it; (2) how far east the dryline makes it. Either way, I think a target east of a line from Canadian-Wheeler-Childress should be pretty good. I'm splitting the difference and am planning on a target somewhere around Wheeler to Sweetwater. This will give me good road options in pretty much all directions, and I would rather be too far south and east rather than too far north and west.

Since it's barely a two-hour drive for me, I'll have the luxury of waiting until the last minute before picking a final target. To everyone that ventures out tomorrow, good luck and stay safe.

 

[Darrin Rasberry]

SPC Day 1 has gone Moderate with a 10% torn bullseye - pretty much right over everyone's target. Dewpoints there are already getting close to 60F. Good luck everyone out there!

Yeah, looks like a hail MOD, not a Tor MOD. Reading the description for today's Day 1 makes sense with it, although I'm not sure as if they won't actually end up hatching it later. After all, if there's to be a small number of isolated supercells producing tornadoes, and not a major outbreak of them, then the 10% is more warranted than a 15%

One thing of note in the SPC Day 1 as it stands at 06Z is that the NAM is favored, and it uses the majority progs that most of us don't have to place the area a little closer to the Texas/OK border along the panhandles. I like that this information was noted, and I think that this is one of the better SPC forecasts I've read as far as chaser-friendly info is concerned, and I don't have a qualm in the least in relying on it this time to verify my guess. Woodward is still looking like the best "assessment point" for a late lunch and current conditions/RUC checkup, and a new target will be assessed at that point if I find enough money in the couch cushions over the next couple of hours to be able to do this "week before payday" long-distance chase in the first place.

 

[Dan Dawson]

The 4km WRF paints an interesting picture, breaking out some supercells around 6-7 PM time frame, then looking like monsters until a dominant one takes root. Those of you pegging Clinton and other parts of W. OK seem to be on to something. The unfortunate part is it looks HP, one of the concerns we might keep in mind tomorrow approaching these storms. Those channeling the US 83 corridor in E. TX panhandle (Canadian-Wheeler-Shamrock) seem to be in the best position to run along with these storms for their whole journey. Because of time, I likely can't get that far west without sacrificing intercepting position.

Its interesting that the EMC 4 km WRF takes that supercell and tracks it all the way into NE OK before dissipating it. Given the continual moisture flux we'll have all night tomorrow night, I can see something like this happening, where one or more supercells remain intense and potentially tornadic all the way through the night (ala 9 May 2003).

One thing to point out here, and I'm not picking on you in particular, but we should be careful in interpreting these high-res model runs as to particulars on supercell structure (i.e. classic vs. HP). 4 km grid spacing is barely enough to resolve supercells; at best you are getting something the model considers a supercell, but since it can't resolve any feature smaller than 8 km on a side (2*delta_x) in this case, it ends up making it larger and meatier than it probably otherwise would be. That is, the updrafts and downdrafts are too big in the model, and the model has to make up for it by parameterizing the effects of turbulent mixing on scales smaller than the grid scale. Unfortunately, no model does this very well. Thus, I would argue that pretty much every "supercell" these runs produce is HP, regardless if the atmosphere actually supports it or not.

There's been a lot of research lately that suggests that grid spacings on the order of 100 m or even smaller are necessary to really get the details of the convection on the storm-scale right (see George Bryan's papers).

Dan

 

[Brandon Sullivan]

Yeah, looks like a hail MOD, not a Tor MOD. Reading the description for today's Day 1 makes sense with it, although I'm not sure as if they won't actually end up hatching it later. After all, if there's to be a small number of isolated supercells producing tornadoes, and not a major outbreak of them, then the 10% is more warranted than a 15%

I'm certainly still amatuer at all this, so not trying to beat ya down. But, I think for now it is simply a case of uncertainties. The SPC outlook does indeed show 45% Hatched Hail, which is represented. Shear is more than adequate for nice supercells, simply put. Continued analysis of 06 Model Suite shows impressive Hodograph curvatures near and just after dark. Surface - 1 KM EHI's spike at this time also. We can see from the models, that while CAPE dips down to near 2000, helicity Spikes in this time frame, which shows the increase in EHI. EHI = (CAPExHelicity)/160000

As the low level jet kicks in, again, the hodo's go crazy and LCL's drop way down. Near and after dark, I certainly see the potential for large tornadoes, some of which could be strong.

I guess the jist of my story is, its early, there are some clear uncertainties, just don't get caught up in chasing SPC probs, I could easily see a 15 hatched tor today.

 

[Brian Stertz]

Looks like the 06z ETA has the main supercell initiation on the boundary and DL across WC/SW Oklahoma...and possibly the extreme E. Texas Panhandle. Things continue to look very intense given the considerable LL broad loop on forecast hodographs all across W. Oklahoma. Right movers will be there certainly and this should bring about very favorable chase storm motions of 15-25mph. This may also bring these monster supercells into C. Oklahoma eventually with a continued threat of baseball or bigger hail and tornadoes moving towards the OKC Metro later tonight. Looks like we'll be adjusting the chase target a little further south down towards I-40 and the town Elk City OK. Plans are to head off from KC in about 30 mins.

 

[Tim Marshall]

TARGET: SHAMROCK, TX TIME OF DEPARTURE: 9 AM - A classic severe weather setup today for the eastern TX panhandle and western OK. PROS- An approaching upper trough with 500mb jet max points toward the TX panhandle on last nights NAM. Ample low level moisture streaming upslope will result in great low-level directional shear. A dryline is forecast to move to the TX/OK border by 00z (per NAM). CONS- High clouds are currently over the target area. Hopefully, they will move out of the way and allow for some surface heating. A cold front is continuing to move southward, just passing Perryton. This could wipe out the northern portion of the TX panhandle if the front doesn't stall and winds don't come around to more easterly. I will be trying out my Sony FX1000 HD camera -which arrived yesterday. tm