April 14-17th Severe Weather (Day 3 Mod)

[patrick7032]

Chicago...I tried to send you a pm but it said you couldn't receive any new msgs...so responded to the chat we had earlier today. Just wanted to let you know about the new msg difficulty.

[Srain]

I would say it is much more impressive than last event ever looked, and I have been surprised by the lack of disco the last two days. My guess is folks are leery after the letdown of that event...and the similarities (especially a few days ago) with the surging cold front. Models have definitely backed off on the density/cold air with this first front.

I am more impressed with the potential ~vs~ last week at this time when we were seeing DP's struggling to reach the 50's in the NW Gulf where we currently are experiencing dews nearing 70 here in SE Texas. Seeing the guidance come into better agreement certainly raises an eyebrow and with the cautious nature after last week, I am more encouraged that this week may bode much better across the. Region. Frankly I would have been shocked if we didn't see a Day 3 Moderate Risk with such differences.

[andyhb]

Beefy numbers on the 72 hr SPC MARS prog, also note the top H5 analog. Also, October 4th, 1998 showing up among the H85 analogs.

 

[baroclinic_instability]

Still some stark differences in the numerical guidance with the upper trof ejection, placement of the warm front, and strength of the lee low. Latest 06z GFS places the warm front clear into N Kansas by late Wed afternoon. By my calculations, that is an incredible 375 mile difference compared to the ECMWF/NAM depiction. The result is much tighter baroclinic zone and stronger pressure falls lee of the Rockies in the vicinity of the trof ejection, with the GFS simulating a sub 994 hpa lee low and some pretty hefty, long low level hodographs/low level shear immediately east of the dryline from N Texas into N Oklahoma. NAM is much weaker immediately east of the dryline, and would support the best higher end tornadic supercell threat across far SW Oklahoma. The GFS verbatim, minus capping concern along the dryline, would suggest the potential (yes, I will use the term) for a much more substantial widespread severe weather event. Even farther N near the warm front into KS, GFS depicts some hellacious low level shear albeit much less instability. NAM and GFS depict widespread 850-750 hpa warm air advection in SW flow east of I-35 with an ascending WCB aiding quite a bit of elevated crapvection through late morning into the afternoon. Even then, impressive MU parcels as low as 800 hpa would have some stout near dry adiabatic lapse rates to work with above the inversion. It seems east of I35, at this point, will be the domain of gigantic hailers with chase threats limited to west of that demarcation. An interesting two days ahead. My gut says a middle ground approach (in between the GFS and NAM/ECMWF depiction will likely be right) in terms of both the placement of the front and the resultant feedback to the kinematic fields (i.e., not as tight of a baroclinic zone near the trof ejection...which would lend itself to less transfer to kinetic energy across the warm sector). But we shall see, it is worth noting the GFS has support from the Canadian, and it has led the way the past two days with a much stronger warm front return. I will say I am far less worried about a surging cold front. Even looking at 00z soundings in the cold sector of the northern plains cyclone, the airmass is nearly dry adiabatic in the dry air and does not in any way exhibit the classic arctic front characteristics with steep inversions and high density air.  This event is really not comparable to the last cold frontal surge

[Ed Lizard]

I'd smooth out that warm nose a tad if I drew this for Dallas and lower the LFC just a bit, but really, I can't complain.

[LocoAko]

I'd smooth out that warm nose a tad if I drew this for Dallas and lower the LFC just a bit, but really, I can't complain.

 

Yep. Really nasty low-level wind field forecast by the 12Z NAM around Lawton, esp if mid-level temps cool just slightly. 

 

[brettjrob]

I thought I might be a tad too optimistic last night, and even I didn't see that SWODY3 coming. The potential remains for an event that would make a D3 MDT look good, and that potential seems to be slowly ticking up. However, I still see a few flies in the ointment that we won't be able to resolve until at least tomorrow evening, most likely. I get the feeling the statistical post-processing must be screaming "outbreak" for SPC to pull the trigger like this.

 

Boy, I can't even remember the last time I saw, for a dryline event, an H85 wind map valid at 00z as impressive as what the 12z NAM paints at H+60. 4/14/12 was similar in magnitude, but slightly veered.

[lowleveljet]

Good read from Patrick Marsh on the progression of Day 3 Moderate Risks

 

http://www.pmarshwx.com/2012/04/spc-day-3-moderates-in-context-what-do-they-become/

[andyhb]

Some kind of sick low level theta-e inflow on the 12z GFS for Wednesday.

 

[JoMo]

The 12z GFS still appears to be doing it's own thing with the 12z Euro/NAM in better agreement. Both the NAM/Euro indicate some kind of warm sector morning/early afternoon convection forming. 

[andyhb]

Some of the soundings from the Red River Valley across the model suite are pretty damn stout on Wednesday, and this appears to be the Euro's favored area for convective initiation.

 

If we were to take a compromise of the NAM/Euro and GFS, that likely puts Oklahoma City right in the middle of potentially the most impressive parameters and in terms of likely convective initiation further south away from the triple point threat in KS/MO.

[OKpowdah]

From the 12z GFS for 00z Thu: pressure / winds on the DT. You can see a number of really cool features coming together.

 

First of all, notice the ridge anticyclonic wave breaking over the eastern Pacific into the Pacific NW. This helps to dig the trough toward the subtropical jet, at which point the phasing of the two quickly intensifies the jet streak (from ~115kt to 155kt in 24 hours).

 

Also fun to watch in the meantime, realtime WV loop: http://www.goes.noaa.gov/HURRLOOPS/hpwv.html ...

You can see the outflow from the convection in the ITCZ extraordinary well, expanding northward and accelerating to the right, forming the subtropical jet streak that will move into the Southwest US on Wednesday. Very cool.

 

Back to the GFS, you can also see the raised tropopause over the Midwest associated with convection firing along and ahead of the warm front. This helps to pump up the downstream ridging, and intensify the polar jet streak ... which increases upper level divergence in the equatorward entrance region, and then goes on to reinforce the thunderstorm activity over the Midwest, and so on.

 

So the jet circulations that develop work in concert, and the convection over the Midwest is crucial in anchoring upper level ridging toward the west ... and then preventing the northern part of the trough from taking off to the east, and cold high pressure surging south. Some nifty positive feedback processes helping out on Wednesday.

 

[andyhb]

Tornado watch out for N TX, Central/E OK, NW AR.

 

http://www.spc.noaa.gov/products/watch/ww0108.html

[Quixotic1]

Tornado watch out for N TX, Central/E OK, NW AR.

 

http://www.spc.noaa.gov/products/watch/ww0108.html

Late one too.  Til 11 pm.

[Indystorm]

Monday's action begins.

BULLETIN - EAS ACTIVATION REQUESTED  SEVERE THUNDERSTORM WARNING  NATIONAL WEATHER SERVICE FORT WORTH TX  417 PM CDT MON APR 15 2013    THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A    * SEVERE THUNDERSTORM WARNING FOR...    JACK COUNTY IN NORTH CENTRAL TEXAS...    EASTERN YOUNG COUNTY IN NORTH CENTRAL TEXAS...    * UNTIL 500 PM CDT    * AT 417 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A    SEVERE THUNDERSTORM CAPABLE OF PRODUCING PING PONG BALL SIZE    HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS    LOCATED 6 MILES NORTHEAST OF GRAHAM...MOVING NORTHEAST AT 30 MPH.    * THE SEVERE THUNDERSTORM WILL BE NEAR...    BRYSON AROUND 425 PM...    JACKSBORO AROUND 450 PM...  

[andyhb]

Moving into an area with ~3000 J/kg SBCAPE per mesoanalysis.

[OKpowdah]

That's a pretty cu field

 

 

[LocoAko]

That's a pretty cu field

 

And pretty convergence, too.

 

 

[OKpowdah]

Cb starting to take off just east of Norman

 

[Indystorm]

Wondering if CINH will be too great this evening to really allow storms to get going.

[andyhb]

Likely, there's not enough large scale forcing for ascent to help break the cap substantially, among other things.

[JoMo]

Wondering if CINH will be too great this evening to really allow storms to get going.

SGF had 88 J/KG of CIN on the 00z RAOB. Probably more farther south and they said that convergence alone probably wouldn't allow storms to form. However, storms should become more numerous to the N of the front once the LLJ kicks in.

[chase_stormz]

So how are we all feeling about the Nam vs. GFS battle for Wednesday? Really debating taking the time/money to go that far from IL.

[Ed Lizard]

Free NWS NexRad picking up rotation now in severe warned cell SE of OKC/OUN.

[OUGrad05]

So how are we all feeling about the Nam vs. GFS battle for Wednesday? Really debating taking the time/money to go that far from IL.

 

I'd hang tight until lunch or 2pm tomorrow.  You can make that drive pretty easily after the data comes in around 2 tomorrow afternoon....just my 2 cents.

[chase_stormz]

I'd hang tight until lunch or 2pm tomorrow.  You can make that drive pretty easily after the data comes in around 2 tomorrow afternoon....just my 2 cents.

 

yea good point. 

[baroclinic_instability]

So how are we all feeling about the Nam vs. GFS battle for Wednesday? Really debating taking the time/money to go that far from IL.

Probably down the middle in terms of placement of the WF in the end, but I am more inclined to lean slightly toward the GFS at this point, especially with a lead wave ejection that far to the NW and the lack of an arctic air mass sinking southward. 

[chase_stormz]

Probably down the middle in terms of placement of the WF in the end, but I am more inclined to lean slightly toward the GFS at this point, especially with a lead wave ejection that far to the NW and the lack of an arctic air mass sinking southward. 

 

LOL everyone is so bad and forth on what they believe. I have trouble putting faith in GFS, but it's just a tough call when you have to make a 10+ hour drive to your target. 

[Jim Marusak]

for wednesday, yea, i'd give it one more day and a couple more runs before deciding on heading.

 

as for tonight's cell near Seminole, OK, I have seen better rotation in the last few frames, looking more straight-line. but that being said, the last shot is looking a bit more promising near Bowlegs, OK. it's interesting to learn grlevel3 2.0 on these cells tonight though (won it over at the MN Skywarn Workshop over the weekend). .

[OKpowdah]

This cell is passing through a narrow stretch of the ripest conditions in OK right now