3/7/06 FCST: Central / Southern Plains

In my opinion, I don't think that Thursday looks very good for a significant severe weather episode. Most of the jet "energy" is forecast to be on the east side of the vort max (according to the GFS), which suggests a weakening storm. Also, GFS forecasts relatively low Tds where the greatest juxtaposition of instability and shear should be.

However, with that said, this morning's ECWMF suggests that the greatest severe threat for Thursday should be closer to the Gulf Coast (with the vort max significantly further south). This could be advantageous in that any storms that would form would be in close proximity to the GoM and the deeper moisture. I guess we'll have to see how this plays out. (It seems like we've been talking about this forever! :p )

On another note, Tuesday is looking more and more interesting for the Southern Plains. Instead of a forecast for slight upper ridging, the ETA now forecasts slight upper troughing. Now, the CIN is still forecast to be insurmountable, but with the trend toward troughiness and the unreliability of model output this far in advance, it is feasible that a subtle wave could develop and set off deep convection. The environment would be fairly favorable for supercells, and perhaps even tornadoes (good deep-layer shear, helicity >200, CAPE > 1000). This day has been overlooked in favor of the more synoptically evident day, but it still bears watching, especially for those of us in the Southern Plains.

Gabe

EDIT: It should be noted that a system as dynamic as the one forecasted for Thursday is bound to produce some tornadoes. However, the threat for strong/violent tornadoes is somewhat reduced when instability parameters are low (though it obviously doesn't preclude such extreme events from occurring).
 
Originally posted by Gabe Garfield
In my opinion, I don't think that Thursday looks very good for a significant severe weather episode. Most of the jet "energy" is forecast to be on the east side of the vort max (according to the GFS), which suggests a weakening storm. Also, GFS forecasts relatively low Tds where the greatest juxtaposition of instability and shear should be.

However, with that said, this morning's ECWMF suggests that the greatest severe threat for Thursday should be closer to the Gulf Coast (with the vort max significantly further south). This could be advantageous in that any storms that would form would be in close proximity to the GoM and the deeper moisture. I guess we'll have to see how this plays out. (It seems like we've been talking about this forever! :p )

On another note, Tuesday is looking more and more interesting for the Southern Plains. Instead of a forecast for slight upper ridging, the ETA now forecasts slight upper troughing. Now, the CIN is still forecast to be insurmountable, but with the trend toward troughiness and the unreliability of model output this far in advance, it is feasible that a subtle wave could develop and set off deep convection. The environment would be fairly favorable for supercells, and perhaps even tornadoes (good deep-layer shear, helicity >200, CAPE > 1000). This day has been overlooked in favor of the more synoptically evident day, but it still bears watching, especially for those of us in the Southern Plains.

Gabe

EDIT: It should be noted that a system as dynamic as the one forecasted for Thursday is bound to produce some tornadoes. However, the threat for strong/violent tornadoes is somewhat reduced when instability parameters are low (though it obviously doesn't preclude such extreme events from occurring).

You stole my thunder about Tuesday. Call me crazy, but I'm prefering the backed winds and persistently strengthening instability/troughiness the models keep giving it. Considering I have an exam until 1:45 on Tuesday, I'm gonna put money on it happening :lol:

To me, if we can get a subtle wave to come through, things look very decent. FWIW, new GFS is now breaking out convection along the dryline on Tuesday whereas before it wasn't :)

EDIT: Granted, the 65/55 temp/td spreads aren't that appealing just yet, but it's definately something that will undoubtedly change one way or another by Tue
 
I agree that Tuesday is looking quite nice actually. The latest NAM is developing strong CAPE and intense shear east of the dryline across most of central/eastern OK and KS. Unfortunately, moisture will be a little limited (NAM forecasting mid-upper 50s in general), resulting in (a) relatively high LCLs (with ~15-20F td deficit, given temps in the 70s to near 80) and (B) very stout CINH. Given that the brunt of the vertical motion from DPVA will slide north of the risk area (mainly along and Emporia), and a dryline that doesn't look too impressive, I think it may be difficult to reduce the cap enough and provide enough surface convergence to allow for initiation. As it is now, the GFS does spit out some convective precip in the warm sector, but I'm not sure how much I trust GFS convective precip forecasts. Looking at initialization, it appears as though the NAM may be a tad too high on the sfc Tds compared to obs (looking at the 60F isodrosotherm, for example), which doesn't bode too well.

I can't chase Tuesday, so I'm going to bias my forecast towards a bust to make me feel better. :lol:

EDIT: I don't agree with the SPCs new Day 2 outlook... Given the setup, I'd at least do a "see text" for the OK/KS area. Sure, it looks capped now, but is there at least a 5% chance that we'll get initiation? I'd assign a nearly 100% chance that any storm that does go in that environment would be severe, so the prob initiation would be about equal to the prob of svr... 5% isn't much, but at least enough to mention the outside probability that a storm does pop through.
 
I can’t help but be entertained by this morning NAM run. For once Oklahoma and Southern Kansas look very good for a chase and that’s back yard chasing in my book.

This run has a better return of moisture than did the 00z run. Forecasting some 60Td in Northern Oklahoma and Southern KS. Nice CAPE values, but as mentioned by other, yet less than last nights run, the CAP will be strong. I think with the amount of vertical shear in place and nice looking hodograph, I can’t pass up this chance. Tomorrow’s analysis will paint the best picture but as of now I am already gone.

Mick
 
Certainly looks alot more promising for Tuesday. The previous runs of the NAM held the CAP quite strong over but it looks more promising now. It certainly looks like the mode is supercellular and likely isolated based on the convergence needed to break the cap in any particular area. The 12z NAM for OKC has 1000 j/kg SBCAPE with only -40 j/kg CINH remaining at 0z. That's with 300 m2/s2 0-3km SRH and a decently oriented deep shear vector. Any storm that forms would be moving into higher helicities. I like Lawton in particular because of the forecasted lift in several levels. At 0z in KLAW NAM shows 30 j/kg CINH, 1400 j/kg SBCAPE and 200 m2/s2 0-3km SRH. Sometime between 0z-03z the NAM shows convective precip between Lawton and OKC. So with some decent moisture convergence, I think it's not unreasonable for intiation by or just after 0z.

One problem that Jeff already hit on is the LCL's. Most soundings show LCL's upwards of 2200-2500m. In Edwards/Thompson paper none of their anaylzed datasets showed a strong or violent tornado in LCL's above 1500m. In fact of their entire dataset the highest weak tornado LCL was about 2400m, which is about what is forecasted for these locations. Granted thats only 200 cases but it's certainly something to keep in mind.
 
Looks like there may be a narrow opportunity for some supercells in West-central Oklahoma. Although the instability axis is a bit displaced from the strongest shear, BUFKIT forecast profiles from the NAM and GFS both indicate approximately 45 knots of deep layer shear along a line roughly from Enid, OK to Frederick, OK. The best hodograph curvature appears roughly along I-40 (Weatherford and therabouts) with increasing 0-3 km helicity in the afternoon, with 0-1 km values in excess of 150 m2/s2. In addition, this morning's NAM showed some nice moisture pooling east of Enid, roughly along the I-35 corridor. My target based on what I have seen so far would probably be Weatherford, as I mentioned above.

I'm still on the fence for a chase as I have three (!) tests this week, but it may be a good chance to take a break. If nothing else, I could wait for it to come closer to the metro and get a chance at some decent lightning or structure shots.
 
Scott,

I get ML LCL heights in the range of 1100-1400 m AGL for multiple forecast soundings across nrn OK/srn KS along the dryline tomorrow afternoon. I suspect the better chance for inititation may be closer the KS/OK border where high clouds should clear earlier in the afternoon compared to areas farther south in OK.

A local hail model and forecast sounding analogs suggest the potential for 2-3" hail in the most intense storms. Additionally, I wouldn't rule out a couple of tornadoes where you can keep surface dewpoints near 60 F with temperatures less than 80 F.

Rich T.
 
Originally posted by Rich Thompson
Scott,

I get ML LCL heights in the range of 1100-1400 m AGL for multiple forecast soundings across nrn OK/srn KS along the dryline tomorrow afternoon. I suspect the better chance for inititation may be closer the KS/OK border where high clouds should clear earlier in the afternoon compared to areas farther south in OK.

A local hail model and forecast sounding analogs suggest the potential for 2-3" hail in the most intense storms. Additionally, I wouldn't rule out a couple of tornadoes where you can keep surface dewpoints near 60 F with temperatures less than 80 F.

Rich T.

Yeah those LCL heights in NRN OK/ SRN KS are much more tolerable, much better than what I was focusing on. Actually some of those soundings are down right impressive.
 
Admittedly, I'm really new to this forecasting thing.

I don't see Tuesday as having the LI to initiate convection.

Wednesday near the TX, OK panhandles looks like chase material to me.

What am I missing?
 
I'm with Mick, I'm as good as gone tommorow. My initial target of choice would be Enid right now, although anywhere up that way sounds game right now...
 
A couple of the previous posters have mentioned tomorrow's soundings looking increasingly impressive. I must agree. I did a quick analysis of soundings from Enid up to Ponca City and my eyes popped out when I saw the hodo's. Furthermore, the cap doesn't appear to be nearly as strong as previously forecasted (looking at GFS and NAM soundings). I have to concur that NW/NC OK is looking much better with concern to tomorrow.
 
I agree.... There is some excellent low-level curvature in the NAM forecast hodograph (for 00z WED) for Enid, OK -- which yields relatively large SRH (with about 180m2/s2 accumulating within the lowest 1 km layer). The forecast sounding shows MLCIN decreasing to ~4j/kg at 00z, with MLCAPE increasing to ~2200j/kg, with a lifted condensation level about 1500 m AGL (assuming a mean parcel 79/57F). If you modify the sounding and moisten the column a bit (increasing the surface Td a few degrees), MLCAPE reaches ~2700j/kg and the MLLCL lowers a few hundred meters.

So, if we can get some localized moisture pooling (to get surface Tds near 60F) and temperatures in the 78F range, then we have relatively low LCLs, in addition to large CAPE and large SRH -- with strong 0-6km deep-layer shear of >45kts -- to easily support supercells, which could rapidly attain low-level mesocyclones given the considerable low-level shear/curvature. All of the forecast soundings around northcentral OK (e.g. WDG, END) shows CIN decreasing to <5j/kg through 00z, so we'll see.

Originally posted by Lance Maxwell
A couple of the previous posters have mentioned tomorrow's soundings looking increasingly impressive. I must agree. I did a quick analysis of soundings from Enid up to Ponca City and my eyes popped out when I saw the hodo's. Furthermore, the cap doesn't appear to be nearly as strong as previously forecasted (looking at GFS and NAM soundings). I have to concur that NW/NC OK is looking much better with concern to tomorrow.
 
Perhaps the best thing going for this system is the fact that I managed to schedule my seminar (which was done in Jan) for the first potential chase day of the year. Dang Murphy's law... always bites you in the butt.

Aaron
 
SPC 1730 Day 2 outlook seems to think there is a narrow axis for a tornado or two. Hatched 15% area from roughly Emporia to SW of OKC. Seems they have a concern on the LCL heights, otherwise the wording would be stronger. After the potential storms form, they say they will weaken outside a certain distance from the dryline.

I'm not free at all tomorrow, as I have class scattered until 5:20. I would be there if it weren't for that, since I'm more familiar with the area than other areas. I agree that things are looking better for tomorrow. Hopefully it holds up.

Main concern of course is convective activity tonight, and how far south and how fast it moves out. ICT forecast discussion noting highs could get into the middle to upper 70s in the warm sector.
 
Originally posted by Aaron Kennedy
Perhaps the best thing going for this system is the fact that I managed to schedule my seminar (which was done in Jan) for the first potential chase day of the year. Dang Murphy's law... always bites you in the butt.

Aaron

Thanks for that!!! Man, the signs are starting to point toward southern KS/northern OK tomorrow. Not the greatest setup in the world by any means but heck, it's early March. What more can we expect. 18Z NAM more bullish with the CAPE over extreme northern OK (~2000 J/kg) with little if any CIN over that same area at 00Z. Of course, that's closing in on sunset this time of year which could present another problem. Will see how the 00Z runs look before making a go/no go decision.
 
Not currently seeing much of an issue with high LCLs, as the target region appears to be <1000 for the most part ... CAPE is quite healthy for this time of year, checking in at >1500 J/kg. 0-1km EHI of 2.3, and >200 m2s2 are shaping tomorrow up as a 'strong tornado' day in my mind. If I could chase, I'd be focusing on the area just west of ICT. Wichita may want to batten down the hatches before the day is done.
 
Originally posted by Mike Peregrine
Not currently seeing much of an issue with high LCLs, as the target region appears to be <1000 for the most part ... CAPE is quite healthy for this time of year, checking in at >1500 J/kg. 0-1km EHI of 2.3, and >200 m2s2 are shaping tomorrow up as a 'strong tornado' day in my mind. If I could chase, I'd be focusing on the area just west of ICT. Wichita may want to batten down the hatches before the day is done.

Not for most of the area south of ICT. See http://68.226.77.253/models/eta/central/CE...ML_LCL_36HR.gif ... With temps in the mid-upper 70s and Tds in the upper 50s to maybe low 60s, dewpoint deficits should be in the 15-25F range, which would support the 1600-2400m ML-LCL forecast by the NAM. Soundings through the Gulf coast region indicate a healthy deep moist layer, with the nice moisture 150-200mb deep (that's nice for May!). My primary concern still concerns initiation. Given initiation, I think the threat for low-level mesocyclones may be signficiant given strong low-level CAPE (12z NAM forecasting >150 j/kg 0-3km CAPE) along with strong low-level shear (0-1km SRH >100 in the warm sector). Forcing mechanisms aloft seem to be weak or against us, as the 12z NAM shows a relative vort min moving towards the target area by 0z, indicate DNVA and attendant subsidence. There's a chance the the souther edge of the stronger vort max to the north may clip the target area, so we'll just have to see. I was reminded that the NAM does have an occassional tendency to overmix the boundary layer (resulting in too-low Tds and too-veered sfc flow). The deep moisture profile to the south may also help keep the moisture Tds from mixing out too much.

Otherwise, there looks to be plenty of tilting and stretching potential, with a very real supercell threat (in fact, I think that'll be the prefered mode given initiation). The dryline doesn't look particularly intense, but then again, models tend to difuse the Td gradient in the vicinity of strong gradients such as that provided by a strong dryline. Otherwise, with a nearly normal / perpendicular orientation between the deep-layer shear vector and the dryline, in addition to the strong shear aloft and decent low-level instability, I would expect to see supercells, though that's entirely hinging on initiation. Regardless of tornado potential, the strong supercell potential (with good CAPE and strong shear favoring strong updrafts) and relatively low wetbulb zero level will likely promote very large hail (3") in any organized supercell that develops. Given the dewpoint deficits, I'd think damaging wind potential is there as well.

As others have noted, the sun does set relatively early. Too bad Congress decided to enact the Daylight Saving Time change in 2007 instead of 2006... Overall, it seems as though the change to DST will occur nearly 3 weeks earlier starting next year, which will definately be welcomed by me since that gives me more time to chase in the afternoon (assuming my classes get out around noon), and I certainly won't miss the hour of sunlight in the morning!

I may virtually target extreme southern KS (perhaps near or just east of Harper county, which almost always seems like a good location for mysteriously favored initiation based on my experience). Again, I'm trying to be as pessimistic as possible sinceI can't chase... My situation is kind of similar to Aaron's, in that I set aside tomorrow back in December... Again, what are the chances that a single early March day could turn out to be a potentially significant chase day? Ugh.

I expect to see a MDT risk should it become apparent that more than isolated supercells can develop. Remember that the categorical risks (SLT, MDT, HIGH) associated with a given set of probabilities changed a few weeks ago. Please see http://www.spc.noaa.gov/misc/SPC_Prob_Conv...e_20060214.html for more information.

EDIT: Reviewing the new tables, I actually must say that I don't think a MDT risk would be issued, since a MDT now requires 15% tornado prob or 45% wind or 45% hatched hail... I do think they would hatch the hail risk, but I can't imagine seeing it any more than 15 given the isolated or widely scattered nature of the storms (maybe 30% if the coverage is more than widely scattered). If dewpoint deficits are more in the 10-15F range, resulting in LCLs that were more int eh 1200m range, I could see a 15% tornado risk IF coverage is more than isolated.
 
Ok so let me get this straight.....Tuesday I have 3 classes ok. One at noon with an exam then another at 3:30 with an exam till 4:45. Then Im free Wed and Thursday. Any day this week but Tuesday and what day does this scenario choose to occur on....yep thats right, Tuesday @#*(#$&)#()*!!!!!

Im with Jeff on this one: BUST BUST BUST Please BUST
 
My hopes for chasing close to home is getting better and better every hour. My original thinking was that the so-called dryline was going to set up in far western oklahoma and my original target was Enid. Looking at latest obs, dryline appears to be evolving in the central Texas Panhandle. Dews in here in Booker have climed by 4 degrees in the last hour and southeast winds are increasing. Dryline is clearly seen on surface observations, Clayton, NM has a dew point of 8, while Canadian, TX has a dew point of 41. Pretty good difference within an 80 mile stretch. My forecasted target as of now is going to be Shattuck, OK. I feel the dryline will swing east pretty fast on Tuesday. With dew points around 60 and temperatures in the mid-upper 70s, Cape values appear to be around 1500 j/kg. I will just have to see the latest runs to determine for sure.
 
Originally posted by CHris Whitehead
Ok so let me get this straight.....Tuesday I have 3 classes ok. One at noon with an exam then another at 3:30 with an exam till 4:45. Then Im free Wed and Thursday. Any day this week but Tuesday and what day does this scenario choose to occur on....yep thats right, Tuesday @#*(#$&)#()*!!!!!

Im with Jeff on this one: BUST BUST BUST Please BUST

You know wishing for a bust for others only leads to future headaches for yourself :wink:

0z runs don't change my mind any, I'm still looking towards Enid or so. LCLs look decent still up that way. I'd be happy with a good looking supercell out in Western Oklahoma myself...
 
If your on the fence on chasing tommorow, consider the forecast sounding for Wichita. Very low LCL's with 2500 j/kg SBCAPE and 300 m2/s2 of 0-3km SRH. The CINH remaining at 0z is quite negliable and with some convergene should see some isolated development.

Virtual Target: 166 Highway/35 intersection in extreme SC KS.
 
I'd be very skeptical of 2500j/kg CAPE being realized in this type of early season event... just a little bit of a negative (be it clouds, slightly less dp, etc.) can absolutely kill these sorts of numbers. That said, I'd be chasing if I didn't have to give a seminar about supercells :shock:

Aaron
 
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