2016-05-16 EVENT: KS/OK/TX

[Brian McKibben]

We are one week out, but the Good For Storms (GFS) model is teasing us again. Lots of abundant moisture working its way up I-35, Tds aoa 70° F. Nice 50 kts at 500mb and decent 850 flow. Lots can change but this is May.

I saw this one on the CFS a while back and it kept popping up and then disappearing on the GFS. I will be keeping my eyes on this one to see if models continue.



And here is a sounding from KOKC to wet your appetite

 

[Royce Sheibal]

Look at your Sounding Analogs....May 3rd, 1999 anyone? I took a few pokes myself and also found May 29th 2004, which was another big day. Considering the activity the day before as well...could we be looking at a tornado event sequence? The time of year is right and the likelihood of a bust during that period is relatively low (storms will fire...somewhere if you drive far enough).

It seems like that might be a good week to spend chasing...Sunday in the PH of Texas, Monday in OKC, moving into the MS. Valley on Tuesday. Finally wrapping up the week with what appears to be 2-day event Possible Next Friday-Sat in KS/NE. Time to plan your hotel reservations and rental cars!

But in all seriousness, it is a really long time away, and the GFS is TERRIBLE with cyclogensis timing. It is, however, very good at ridge/trough locations and amplitudes, so it's fair to say something big is likely going to go down, but we've got a 12-24 hour margin of error at this point.

 

[Eddie Natenberg]

Not sure if my interest in this event is 'clouding my judgment' and making me more biased to wish casting this event but I'll say this. I'm shocked how closely this analogs may 3rd, both in bulk indicies and qualitatively, at least in dynamics. Mostly due to the low amplitude of the trough allowing for waves to propagate ahead of the low pressure, which from experience seems to create a decent mix of CAPE and low level shear. Anytime you don't get a large high pressure to the east I tend to think it will favor a progressive system with a more outbreak scenario. The only thing missing that is that usually present for big outbreaks is a second day event allowing for a notcturnal MCS to move through on day 1 and clearing the skys for day 2. I am not seeing that for this event so morning/noon convection might be an issue (actually GFS precip is confirming this). So I guess this should be watched. If things change in the forecast and you get a strong shortwave to clear the skies before noon then all bets are off.

 

[Trey Thee]

Not sure if my interest in this event is 'clouding my judgment' and making me more biased to wish casting this event but I'll say this. I'm shocked how closely this analogs may 3rd, both in bulk indicies and qualitatively, at least in dynamics. Mostly due to the low amplitude of the trough allowing for waves to propagate ahead of the low pressure, which from experience seems to create a decent mix of CAPE and low level shear. Anytime you don't get a large high pressure to the east I tend to think it will favor a progressive system with a more outbreak scenario. The only thing missing that is that usually present for big outbreaks is a second day event allowing for a notcturnal MCS to move through on day 1 and clearing the skys for day 2. I am not seeing that for this event so morning/noon convection might be an issue (actually GFS precip is confirming this). So I guess this should be watched. If things change in the forecast and you get a strong shortwave to clear the skies before noon then all bets are off.

Good point on the morning convection but I would say sitting this far out lots can and probably will change. Even with morning junk, if it clears off by noon as you say, things could be potent. May3 pops up fairly often, a couple times a year in analogs usually...once we get within 48 hours I'll start taking the analogs more seriously.

This certainly looks like the most potent setup of the year, at least from my view...too bad I won't be able to chase.

 

[Brian McKibben]

Even though this isn't in the NAMs range yet... i have been comparing the 84 hr forecast of NAM and GFS since yesterday. So far, the 84 hours are lining up ok. The NAM looks to have a bit stronger 500 mb flow too. Friday morning runs will be interesting to look through.

One plus is that the GOF looks to stay primed so we should at the very least gets some decent moisture advection.

Lots of change possible but this day keeps popping up on the GFS since the 12z run on Tuesday.

 

[Jeff Duda]

Not terribly encouraged from the overall downward trend in shear I've seen from the GFS over the last several cycles. The trough is still wobbling around from run to run but also appears to be moving from an actual shortwave to more of an embedded speed max in the h5 flow, with progressively less in the way of a zonal height gradient with each new run. This raises questions about 1) location of the event, 2) whether or not supercells will even be the storm mode, and 3) capping.

Moisture isn't a guarantee with this one either. The current front looks to sweep across much of the gulf over the next few days with a big ol' anticyclone sitting over the western Gulf until Sunday or so. It does look like there will be a narrow tongue of onshore flow across the far western Gulf throughout this time, so much like last weekend's system, it may appear that moisture won't make it, but perhaps it will magically appear the day of. Not entirely encouraged by the surface pattern showing up at 00Z Sunday evening from the NAM either, as it seems to be trying really hard to bring back winter for some odd reason.

 

[Andy Wehrle]

NAM looks a little more on board as of 12Z this morning, highlighting the southern Texas panhandle. GFS has been relatively consistent with this system, although 500mb winds continue to look modest, it's spitting out some enticing hodographs at the low levels.

 

[Trey Thee]

NAM looks a little more on board as of 12Z this morning, highlighting the southern Texas panhandle. GFS has been relatively consistent with this system, although 500mb winds continue to look modest, it's spitting out some enticing hodographs at the low levels.

difference in moisture return is pretty stark, the NAM has 60* dew points struggling to get to I40 and the GFS has them all the way to the KS border with a sharp gradient. DP's in North OKC/Edmond are 9* higher on the GFS than the NAM. That's pretty significant. Normally the NAM is overly aggressive...we'll see if it turns the corner soon...

Looking like this could shape up to be a panhandle chase into western OK on Monday, with a setup in Arklatex Tuesday....

 

[JeremyS]

The placement of the best moisture and dynamics still remains different between the NAM and the GFS. However what concerns me and was mentioned by the SPC is that the NAM and the NAM 4K does not break out any precip during daylight. If I'm going to drive 9 hours I don't want to see storms at night!


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[Bob Schafer]

This is why I try to not hyperventilate about models more than a couple of days out. This forecast has changed a lot, at least based on the GFS and now NAM. New Mexico is now in play, is the current target, and initiation is of no concern. I wonder what it will look like in another 6 hours; probably way different.

 

[JeremyS]

I should clarify, the models do break out precip in the late afternoon, but in southeast Colorado which look to be elevated storms with little tornado risk. The dry line looks to remain quiet through daylight on the NAM and NAM 4k. The GFS might be trying to show something at 0Z due east of the surface low in the Oklahoma panhandle, but the question would be how long would it stay in the warm sector before crossing the warm front?

 

[Sam Lillo]

I should clarify, the models do break out precip in the late afternoon, but in southeast Colorado which look to be elevated storms with little tornado risk. The dry line looks to remain quiet through daylight on the NAM and NAM 4k. The GFS might be trying to show something at 0Z due east of the surface low in the Oklahoma panhandle, but the question would be how long would it stay in the warm sector before crossing the warm front?

I would be wary of using the NAM for judging convective initiation. The BMJ parameterization scheme being sensitive to mid level moisture will frequently underplay dryline convection.

To your last point, one pro for Monday is that storm motions look pretty slow, giving more residence time in the warm sector and best instability.

 

[JimMartin35]

Today's 18z GFS showing a more favorable wind profile + plenty of surface based CAPE for Monday evening...

 

[JeremyS]

0Z runs of the NAM models are in and again don't show any precip breaking out along the dry line before dark. I can understand if that model has issues with dry line convection but of course I've seen these models spit out storms plenty of times too along the dry line. Does this concern anyone else there's no precip showing up on every run of the NAM?! I see plenty of vertical velocity and it is a sharp dry line with a nice bulge to it so curious if this is just a model issue


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[John Moore]

GFS looks a bit happier on the dryline 0-3Z. 4K convective allowing NAM, however, does not. I don't know if it shares the weakness on CI of the main NAM model, though.