4/22/04: FCST OK / N TX

[Jeff Snyder]

I have been delaying starting a thread until nearly 42-48 hours out, and I think the ETA is locking into a possible severe weather and tornado threat on Thursday. The front the is cruising through OK tonight is progged to stall tomorrow, and lift back north on Thursday. The ETA develops significant instability across southeastern OK by 18z Thursday, with CAPES >3500. As the warm front continues northward, this instability will spead northward behind it. By 0z, the warm front is progged to be near a Tulsa - south of Enid line.

The ETA builds strong instability behind the warm front, with a small area of CAPE >3500. There is very high helicity along and north of the front. This time, however, there is actually a decent area where there is signficant instability juxtaposed with signficant shear. Check out this graphic of CAPE/helicity/SWEAT from wxcaster.com (I've saved it to my site so that the actual graphic doesn't change next model run)... While mid-level flow is relatively weak, it is on the nose of an approaching jet streak. And actually, the ETA is forecasting 50-65 kt 0-6k deep layer shear!

Finally, LCLs should be relatively low, with upper 60s along and south of the front. FINALLY some truely humid air! We could actually get Tds >70 by friday, but that'll probably be another thread in the coming 36 hours...

Just some graphics for those who are interested:

 

[Dan Robinson]

SPC just extended the Moderate Risk on the Day 2 all the way to eastern Kentucky.

Haven't had a chance to really look at this, but the ETA breaks out an area of intense precip into this area by tomorrow. Moisture is lacking today, but it looks like this will improve tomorrow. Could be an interesting day, I will likely be out in Kentucky somewhere tomorrow.

 

[Kevin Scharfenberg]

The shear profiles Thursday look fairly similar to the profiles from Wednesday, so perhaps another day of non-tornadic supercells. This time, there is no strong shortwave trough progged to move into the region late in the afternoon, so while storm initiation before dark is not a given, hopefully any storms that can develop will be more isolated. I don't see any reason why the moisture will not continue to be meager (true tropical moisture still out of reach), so look for more high bases and cold, wet RFDs if storms can get going.

 

[Dan Robinson]

(Not sure if this post warrants another thread due to being this far east - if so feel free to move it if needed.) Regarding the eastern end of this event, the moisture situation is still not improving all that much. In fact, the higher elevations in the central Appalachians are showing DPs in the mid 30s (is this typical?). Earlier this afternoon, two stations in the NC mountain regions were showing dewpoints of 28F. Granted, these are the mountains (3K to 6K feet) but those seem extremely low by any standard. In the lowlands a little farther west things are slightly better, but not by much (widespread 50F DPs).

Pros: The ETA seems to keep most of the CAPE and precip in extreme western KY, but shows a nose of 60-65F DPs reaching up into KY, Ohio and WV. And we still have the stalled front on the doorstep. This along with the shear profiles seem to be the only potential positives. Cons: The RUC doesn't seem as optimistic about improving moisture, and the actual obs are showing marginal dewpoints (although we're currently in the nighttime hours). Looking at the IR satellite and ground observations, there is a lot of cloud cover hanging around despite some areas of mostly clear skies - so we might also have trouble getting any decent heating in the eastern portions of the risk area. I'm still anxious to chase, but I'm thinking that the moderate risk may be out of most of Kentucky by the 0600Z outlook Hope I'm wrong though!

That's my novice assessment, corrections are welcome and appreciated.

 

[Shane Adams]

Having yet to see a 0Z RUC run, I'm basing my current opinion on the 21Z RUC/0Z eta runs. VVs and CAPE spikes are nicely juxtaposed across east central/east OK per ETA by 0Z, while the RUC VVs are the same at 21Z, but further south and west.....this seems to indicate that these models will both agree on things by 0Z.

21Z RUC has a huge swath of CAPE AOA 3000 j/kg, right over the maximized VV/precip spikes. A check of current surface data shows moisture already pooling in that same area nicely; low 70s with low/mid 60s Tds are already noted across SC OK.

Will definitely wait until the next RUC run to start making finalized plans, but once again this lookd like a relatively close chase. I don't know what happened with the Day One/tornado probability graphic pages on SPC (they are both out to lunch), but I'm guessing it's still a 5%, if for any other reason, because of yesterday's non-producing PDS situation.

I see a lot of yesterday in today, but with higher CAPE progged over initiation points, I feel today's instability could prove sufficient for more-isolated storms. If we can get a few discrete cells up early and keep them alone, think we'll be in store for a few tornadoes.

 

[Kevin Scharfenberg]

Two boundaries are interesecting near Yukon at this hour. The front extends from east of Red Rock to Yukon to Frederick, and a nice confluence line extends from Yukon to south of McAlester. Moisture is really pooling along the confluence line, with some mid-upper 60s on the mesonet. I would expect the dewpoints to mix out into the lower 60s during the day.

Deep-layer shear is again favorable for supercells. Dewpoint depressions will continue to be high today thanks to the marginal moisture, and low-level shear will again be weak, so I'm thinking the storms will once again tend to produce wet, cold RFDs but perhaps extensive hail.

The snyoptic-scale forcing will not be as strong today, so perhaps the storms will be more isolated.

The best chance of storms will be south of the front and east of the confluence line. Target: Seminole, OK.

Good luck to anyone who can chase! Even though today looks a lot like yesterday on paper, that doesn't preclude an unforeseen "accident" happening!

 

[Chris C Sanner]

Today is Thursday right?! A lot of the same stuff as yesterday it looks like. I'm really liking Southern Oklahoma along the front today. If we can keep these storms more isolated we might get a tornado out of these today. Right now dewpoints are 66-68 along southern oklahoma. If we can raise those somewhat and we keep the sky clear, it could be another big day. The clouds are broken allowing intermittent (sp?) sunshine right now, so if the clouds clear as fast as they did yesterday my initial target will be somewhere in Southern Oklahoma, probably a start off in Velma and then go from there.

 

[Aaron Kennedy]

Current setup (brief overview)...

Right now we have our largest dewpoint gradient along I35 to Norman, ESE to McAlester. Along the Red River, dewpoints are in the mid 60s. As of this afternoon, the boundary shouldn't move much. I still like the intersection of the dryline/front.. and points NE... which should be somewhere near somewhere along I35 south of Norman. (Ardmore-Ada?)

Expect initiation mid afternoon. RUC is breaking out precip all over. Let's hope its just a bit less than yesterday. I feel that if we can keep things a bit more isolated, perhaps our tornado chances will be a bit better.


Target: argh.. these close to home chases. I will probably wait till I see the cu fields start to take shape and then make my decision. As of now though, I would pick Ada. (corrected from Ardmore... a bit far from the front)!

What it really comes down to is the fact I won't be able to chase from April 29-May 10. Got to go chasing now. I have nothing to lose.

Aaron

 

[Shane Adams]

Well, Kevin likes Seminole and Aaron likes Ardmore-Ada. LOL, my initial target about an hour ago was Pauls Valley. I like the RUC breaking out precip by 21Z south of OUN along 35, but I'm concerned about the positioning of the front relative to the preciptation. Those northerly winds behind the front seem to want to invade my target area well before dark, so I am thinking of shifting east a bit, just for insurance. Especially due to the fact that today seems much like yesterday, and if so, not being right on a storm when it goes up won't be an issue.

I'm the eternal optimist, so I'm counting on (hoping, really) that jacked up areas of CAPE will influence a more isolated nature of convection. At least today, we'll know to go home if there's 15 severe warnings within the first hour. Will keep monitoring from homebase (just like yesterday), and make our move accordingly.

 

[Kevin Scharfenberg]

The triple point has translated northeast and is now just west of Chandler. Dewpoints are still holding in nicely, but I would still expect some mixing out later.

0-1 km shear still stinks on the Purcell profiler, but is much better on the Haskell profiler. In fact, the current Haskell wind profile is better than anything I remember seeing yesterday.

I look for storms to develop along the convergence line not far east and southeast of OKC/OUN and move east into an area of better low level shear. My target is now Henryetta, Oklahoma, with a slightly higher confidence for tornadoes.

 

[Jeff Snyder]

Dewpoints are actually increasing across the area. Now 81/70 south of Ardmore. Upper-60 tds advecting just south of the boundary that along I-40. RUC has CAPE >3000 by afternoon. Shear will likely be enhanced near any boundaries this afternoon. I am getting increasingly optimistic now... I'm thinking probably east on I-40, with a slight tendency to want to drop a little south of I-40. I'm worried about the cold front and convergence along it busting too many cells (similar to yesterday along the dryline), but I not too concerned about that yet. Will likely head out mid afternoon....

 

[KMcCallister]

Since I have a test this evening, I can't go anywhere. As of early afternoon with the boundary moving SE through OKC, my original "virtual target" would shift too far east. I'd now call Mcalester my "target city".

With the veering surface winds at ADM, I am not optimistic of any storms in quality chase country.

Enjoy the trees everybody!

Happy hunting everybody!

 

[Shyanna Busch]

Is anything going to be firing up in SW/West Central MO this evening? All day we've had small thunder storms building. With evening approaching, is there anything to look out for? I don't know how to read the maps well enough to figure it out myself.