2013-04-09 FCST: CO, NE, KS, OK

[Tim Nendick]

The second day of the first plains set up for the year has my attention.

The 4/4 0Z GFS is showing a robust area of >60ºF Tds stretching well into Iowa, and a well defined dryline draped across KS, OK, and TX at 0z on 4/10. A greater than 100kt jet streak is ejecting out of the base of the trough, and should aid in some synoptic forcing that may be absent on Monday.

A 996mb low is forecast to be present near topeka ks at 0z along the dryline with an appreciable 850mb vorticity signature, which should aid convergence along the boundary, and may help to bulge it some.

The GFS is currently showing convective initiation along the dryline in KS and into KS between 18Z-0Z in response to strong diurnal heating which should help overcome a finger of 15ºC 850mb temps; this is reflected in an absence of CIN by 0Z on the 10th. Along the dryline, 500mb temps of <-15ºF are present, which should enhance lapse rates and aid instability, which is currently showing values of ~1000J. I would expect large hail to be a major threat because of this.

Bulk shear from sfc-500mb of about 50kts and surface LCLs of less than 500m should further enhance the severe potential.

The model sounding near Holton, KS, demonstrates the convective initiation/cap break nicely.

the hodograph at 0Z is worth noting as well.

I would expect tuesday the 9th to be another tempting set-up that should produce nicely is storms can remain discrete.

 

[Tim Supinie]

I'm not a huge fan of the massive anti-cyclonic kinks near 700 mb in the hodographs Wednesday 00Z (Tuesday evening). Seems like more often than not, those types of hodographs result in cells running into each other, with nothing able to get organized. Those types of hodographs are apparent all along the dryline from eastern OK to northeast KS. It would make me worried about a junkfest. Low-level lapse rates are better farther north (northeast KS as opposed to eastern OK), but I'm not sure that's reliable on a 120-hour forecast.

Disclaimer: I can't chase on Tuesday.

Also, check the date in the title.

 

[Trey Thee]

I'm not a huge fan of the massive anti-cyclonic kinks near 700 mb in the hodographs Wednesday 00Z (Tuesday evening). Seems like more often than not, those types of hodographs result in cells running into each other, with nothing able to get organized. Those types of hodographs are apparent all along the dryline from eastern OK to northeast KS. It would make me worried about a junkfest. Low-level lapse rates are better farther north (northeast KS as opposed to eastern OK), but I'm not sure that's reliable on a 120-hour forecast.

Disclaimer: I can't chase on Tuesday.

Also, check the date in the title.

With the current location of the system, I'm also not putting a lot of weight on the forecasts yet, only thing we can take away is svr weather appears likely. Nailing down the location and mode is tough right now. I am also in agreement with you with regard to the kinks in the HODO's.

I'll start making decision (ie take off work or not on Tuesday afternoon) when the data starts coming in after 8pm tomorrow evening. At this point it looks like the storms will have trouble staying discreet and we could have a mess of convection out in front of a squall line.

We will have three days of good moisture return here in the Tulsa area and this time of year anything is possible. CAPE values aren't overly impressive though...at least not showing up yet. HODO's aren't great, SKEWT's aren't great. We just need a better handle on the system which we won't have for another 24-36 hrs.

 

[Mike Smith]

I've had a chance to look at the 4km and 12km NAM as well as the 00Z soundings from Monterrey, MX and south Texas. Not worried about moisture Monday. Based on what I have seen, if I had to issue an old-style tornado watch for Monday: 70 mi. either side of a line from Larned, Kansas, to 40 WSW of OKC. Put another way, I'd outlook it as 15% hatched.

 

[jeremy wilson]

I've had a chance to look at the 4km and 12km NAM as well as the 00Z soundings from Monterrey, MX and south Texas. Not worried about moisture Monday. Based on what I have seen, if I had to issue an old-style tornado watch for Monday: 70 mi. either side of a line from Larned, Kansas, to 40 WSW of OKC. Put another way, I'd outlook it as 15% hatched.

I agree Mike, although I think it'll be more like a 10 hatch. There could be some nice storms around the cf/dl intersection. Regrettably, They could be very near the OKC metro. On a slightly side/optimistic note, much needed rain could come to a lot of our drought stricken State. Regardless Tuesday will be a chaser choked nightmare, be careful out there.

 

[Chris Wilburn]

I think the best play for tornadoes is in SW OK along the dryline before the cold front takes over. Moisture and instability shouldn't be an issue. The directional shear is less than ideal for tornadoes, but I do expect a handful of reports. Capping shouldn't be an issue like Mondays setup so at least that is good. I would say Weatherford down to Lawton or just westr of there is a good starting point. The cold front will see plenty of storms and more coverage, but more isolated storms capable of tornadoes will be located along and west of I40. It will be nice to actually dust off the equipment and shake off the rust. The trough is a bit too amplified which is creating more southerly 500mb winds and thus hurting directional shear. It should be a fun day that's for sure even if it's just for us all to test the equipment and get our feet wet for the 2013 chase season.

 

[Kelly Sugden]

Based off the ECMWF...
Strong pressure rises behind front, isallobaric wind response, tons of mixing along density gradient, shear vector aligned nearly parallel to 500-300 hPa mean flow. Meh.

Edit: that was for Kansas... even going farther south into Oklahoma the upper level winds back. HP/QLCS mess.

 

[jeremy wilson]

Without going into extreme detail, Here's my take.

After looking at latest models, my best guess is several tornado reports from the SW Oklahoma area. Maybe even as far north as El Reno. From my past 15 years of chase experience, tomorrow has the potential to produce a few strong tornadoes. Then again, it could be a squall fest after dark. Game on!!!

 

[John MacKay]

I agree with the take of Oklahoma being the best shot at tornado potential. The most recent 00z runs have hinted at a window in OK where isolated development on the dryline could occur. The wind dynamics further up in the atmosphere, though, leave more to be desired. Many setups with that 850 mb-500 mb spread tend to have trouble with the storms staying isolated enough from each other to maintain circulation centers in cells. Even so, many of those same setups provided strong tornadoes. My inclination would be to target OKC and points SSW of there to the Red River.

 

[Tony Gilbert]

SPC now ramping up today's severe potential nicely! I won't duplicate what the SPC are saying because we can read this straight from their page. Though, in addition to this there are certainly some good positive aspects to this outlook that catch my attention for OK;
Earlier models were not clear regarding the long wave to short wave upper transition. This now looks much clearer based on the NAM. A strong divergent vector above 500mb will assert moderate upper lift to 200mb where cloud tops are expected reach. This upward displacement should at least filter downward to the mid level increasing the upward velocity of updrafts hence a significant risk of large hail. Forecast soundings south central OK predict low LCL, probably below 850mb. This combined with good low level hodograph signatures and workable moisture certainly creates a good environment for tornado genesis. Current thinking would see a favourable environment primarily SW OK by late afternoon. Though target zones are better located using RUC or HRRR when they come into play. With just a 90 deg turn of directional shear up to the mid levels we might see some train echo motion of storm cells with any cell developing to the east of the line becoming dominant. So in short, alot of decaying cell activity west of the SSW to NNE orientated line.

 

[Trey Thee]

This system is not looking impressive this morning. IF and it's a big IF something can get going in the warm sector it'll have a chance at producing significant severe weather. However, the significant cap is likely to prevent anything from going in the warm sector until it begins to errode late evening. At that point one or two cells could pop in front of the main system.

Once the dryline is over run by the Canadian front things will line out and even then I'm not sure we'll see a severe squall line given the placement and speed of the system. It could simply choke off a lot of the warm and moist air resulting in a heavy rain event. Perhaps I'm just being a negative nancy on this system but at this point I'm not buying the hype.

 

[Marcus Diaz]

I'm sitting at work and by 8am the cold front was screaming through here in AMA. If anything goes it'll probably be confined to souther OK/N TX. But with the cold front 8 hours ahead of schedule (forecasted to come through here around 21z) I don't see a good supercellular storm popping anywhere before the cold front ruins the day.

 

[Brian McKibben]

Just looked at the models (NAM, RUC, RAP, WRF, HRRR) and they all pop convection on the cold front. The front is way further south and than it was forecast. Therefore, the models show the only dryline play will be from SPS south to ABI. Everywhere in OK looks to be a cold front play. I am not too optimistic on tornado potential in Okla. because of this. The mesonet shows the CF already pushing into NW Okla. with winds screaming at near 40 mph behind it. Models indicate front should be in Central OK by around 2-4pm. With the CF's current position and a movement of 35 mph this seems very likely.

If I was chasing I would target NW TX. Poor road network down there though. Good luck to all who do chase.

 

[Tony Gilbert]

Agreed, based now on the RAP and HRRR, certainly appears less convective than the earlier NAM predictions. Vis Sat currently shows CF rapidly moving eastward. Though the most recent model output holds the frontal boundary almost stationary on a SW to NE train motion by 22Z primarily within the SW OK quadrant. The lack of appreciable forward momentum could well force any building storm cell development to undercut themselves as they transit NE on a parallel line. The HRRR likewise seems to be ingesting this latest update of conditions and is pushing the CAPE out ahead of the CF frontal boundary. This is certainly not a good advance to the forecast! Ironically the vertical shear in line with the cold front is exceptional ATM though sadly the lack of sufficient overlay to SBCape could just deliver strong winds and heavy rain to most parts. Much will now depend on the eastward speed of the CF.

 

[E Hale]

2013-04-09 FCST: TX / OK / KS / NE

What on earth is going on? This system is bizarre to me. Forcing is clearly present but the front is undercutting updrafts? Is there still a chance that isolated cells could develop in the warm sector out ahead of the front? It seems like some CU pops up and then dissipates in Eastern OK. Cape high, low level winds adequate and not terribly strong cap.