4/1/10 FCST: TX/OK/KS/NE/SD/MN

[David Goines]

Even though I wont be chasing tomorrow, western OK is where I would be heading if I were. I know it's an "off-hour run" but the 18z NAM+30hr has an area of 1250+ CAPE with manageable CIN values.
Here is a sounding from the Altus, OK area.

 

[Skip Talbot]

Well, we had a few interesting runs that hinted at areas up north and maybe teased us with less of a cap down south. I can't bring myself to pull the trigger on this setup though. The 0z NAM has further strengthened the cap across the entire dryline and the warm front way up north. If I saw the NAM trending towards weakening the cap, I would be more optimistic. Its done the exact opposite, however, and I'm fairly confident this is going to be a cap bust. The NAM, GFS, and 4km WRF refuse to break out precip until well after dark. You can choose to ignore that, but with a cap index of 3 or greater and the main energy from the shortwave trough still well off to the west and pretty modest dewpoints on the dryline, I don't think we will have the forcing or the convergence to overcome that stout cap.

I've also been comparing surface obs with what the NAM has been forecasting from runs 12 hours earlier, and its way off. Its over-forecasted dew points by as much as 10 degrees in places. This setup was already teetering on the edge, but to have that kind of discrepancy in the dew points really makes me doubt anything is going to come of this setup.

 

[Jason Boggs]

After looking at the recent model runs, I'm still planning on going out and hopefully making it worthwhile.

I think with the moisture in place along with daytime heating, the cap may break allowing for a storm or two to go up. The highest forecast CAPE values are in the Vernon, TX vicinity, due to the higher heating and dewpoints. I definitely won't be surprised if no storms form, but I'm a storm chaser, and busts come with the territory.

As far as tornado potential...I think with the great shear in place, rotating supercells will be the dominate form if storms can develop. I wouldn't be surprised if a rogue tornado occurs somewhere along the dryline tomorrow. Hopefully it occurs near Vernon,TX because that's most likely where I'll be. I'll update before I leave if things change.

 

[Rich Thompson]

This sure looks like a cap bust to me. The EML is quite warm and well established already, and it won't be going away. Meanwhile, moisture return is rather meager compared to the warmth of the EML, and there's no easy fix with the tropical moisture still way off to the south. The model forecasts of convective initiation tomorrow night seem to go along with the arrival of the stronger ascent/cooling aloft from 06-12z from western KS into western OK. I'm just not convinced that the dryline circulation will be deep enough/strong enough to support even isolated storm formation during daylight.

I have no intentions of chasing this setup, though having to work tomorrow night makes that decision easy. Still, I'd only chase this if I really wanted to drive a few hours and chunk rocks at power poles!

 

[Jason Boggs]

This sure looks like a cap bust to me. The EML is quite warm and well established already, and it won't be going away. Meanwhile, moisture return is rather meager compared to the warmth of the EML, and there's no easy fix with the tropical moisture still way off to the south. The model forecasts of convective initiation tomorrow night seem to go along with the arrival of the stronger ascent/cooling aloft from 06-12z from western KS into western OK. I'm just not convinced that the dryline circulation will be deep enough/strong enough to support even isolated storm formation during daylight.

I have no intentions of chasing this setup, though having to work tomorrow night makes that decision easy. Still, I'd only chase this if I really wanted to drive a few hours and chunk rocks at power poles!

Really I agree with what you said here Rich. Maybe I'm just getting my hopes up too much, but I'm willing to take the risk. Td in Vernon right now is 50, so the moisture is definitely increasing with the SE surface winds. Your right that the main energy won't be in until later in the evening /night, but maybe if things come together just right, I'll be video taping a supercell...or getting my arm in shape. Only time will tell.

By the way Rich, thanks for sharing your thoughts on possible events. It's always interesting to see what you have to say.

 

[Patrick Marsh]

Similar to the post that David Goines linked to previously, last night I did another post on how a good meteorologist will interrogate model output in such a way as to gather insights as to what model processes are at work. This allows for a more robust conceptual model of the event at hand.

I won't rehash the entire post here (it's fairly long), but it is based on trying to predict thunderstorm initiation along the dryline during the afternoon on 1 April. The highlights:

• SW to NE oriented dryline is forecast to develop from Texas northward
• At 21 UTC 850/700mb convergence is forecast to be pretty abysmal along the dryline
• By 00 UTC 850/700mb convergence is forecast to strengthen along the dryline (substantially at 850mb)

Consequently, the SREF did not have a single member convect in this area between 21-00 UTC. Between 00 UTC and 03 UTC, the SREF does have a few members that convect, and even more members between 03 and 06 UTC.

Does this mean there won't be a storm along the dryline? No. Model resolution is just too coarse to say that. However, it does give a pretty strong signal that large scale forcing alone won't be enough to overcome the CAP. People will need to favor areas where local effects can enhance dryline convergence.

Check out the entire post here: http://www.patricktmarsh.com/2010/03/day-90-thursday-evening-severe-risk/

Just my lousy $0.02.

EDIT: I should have added, this analysis is done using yesterday's 12 UTC NAM and 15 UTC SREF. I don't think much has changed since then (although, I haven't looked this morning), so I feel it is still relevant.

 

[Tim Marshall]

Agree with Rich T on a daytime bust, so I won't be chasing today. I still think there is a good chance of convection breaking out over night -when I will be sleeping. This system is poorly timed, and low-level moisture is starting to return from the cool Gulf. Friday looks like an early squall line, but I might chase it anyways. Will monitor for now.

 

[Brendon Lindsey]

4/1/2010 NOW; KS/OK/TX

Well the show hasnt started yet and I doubt it will before dark but, It is interesting to see the area of 2000 J/Kg of CAPE in west central OK and the instability elsewhere got so high. Comon RUC... Cin is eroding as we speak. In the area of max instability, the high deck of clouds are whisping overhead, which will not help the situation. I believe we could see a few supercells before it goes linear. I am in Enid and will be chasing tonight's show. If anyone else is heading out in this area shoot me a PM.

Lift is not great... -3 on ks/ok border, That will only enhance as more forcing gets here. I would say the show starts on the OK/KS border...

New RUC hinting at before dark show.

 

[Andrew Pritchard]

Not sure where you're seeing that before dark hint as what I'm seeing has things extremely capped off until well after dark. The RUC loves to show minor qpf marks but you should be wary of calling this the "show", as well as using that alone to try and determine convective initiation on a day such as this as stated above by Rich. Looking at current data I see nothing that suggests severe storm development in the next 6 hours.

SBcape values are impressive, but MLcape values are much lower and realistic. Cinh remains off the charts, 700mb temperatures near 10F over much of the area, LCL's over 2000 and LFC off the charts as well. I'd be floored to see a supercell form before dark, let alone enough for something to go linear.

Enjoy the sights and the feeling of being out, and then the potential lightning display around midnight if you're lucky.

I hope I'm wrong for the sake of those who made the trip, but this looks like a longer shot at getting something to develop than those Nintendo number Iowa days in July.

 

[Rich Thompson]

Cirrus sitting over the dryline, poor low-level convergence, and marginal moisture tell me it was a good day to hang out at home. I recall the NAM and GFS forecasts from 1-2 days ago showing ridiculous 62-66 F Tds across IA by 00z this evening. The observations will easily fall 8-10 F below those values, aside from the awful AWOS sensors with the overblown Tds near 60 F.