3-28-07 FCST: SD / NE / KS / OK / TX

[Mikey Gribble]

I must have misunderstood what you meant when you said...

"Deep layer shear and storm motions are much better for chasing."

Relative to what? The northern target or the past model run? Neither is different.

I agree that storm motions are more parallel to the boundary farther North and that may cause a problem with convective mode, but there are also some advantages to the northern target too. I think those advantages outweigh the 12 degree difference in storm motion at this point. I'm not even sure right now that I'll go as far North as Hays. The main things I still want to see before I pick my initial target is the WRF precip. graphics tonight (and the other model runs) and moisture distribution tomorrow morning.

 

[Brandon Lawson]

Someone slap me.

The new NAM has me really excited for southwest oklahoma. Surface winds are almost out of the southeast . Cape values are still really high and helicity values across all of western oklahoma range from 200 to 300. Dewpoints are all in the low 60's. What's not to like about that? Someone please bring me back down to earth and tell me if I'm missing something here. Forecast sounding out of Frederick, Oklahoma looks pretty darn enticing.

http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=024&STATIONID=KFDR

 

[Donald Giuliano]

After seeing the 00Z soundings, I was expecting the NAM to be impressive due to the very good agreement between the 700mb temp/wind fields and the 12hr NAM forecast this morning. But this looks even better than the 12/18Z runs of the NAM. My concern about the system coming out even slower has mostly been alleviated, because the CAA at 700mb on the base of the trough is intense, and will force the upper jet to propagate further east due to changes in the thermal wind, despite the apparent lack of CAA at 500mb. The evening soundings confirm this feature, and the RUC/NAM are in very good agreement about the 700mb cold front continuing to press east through 12Z.

As I look at this situation, all I can say is "wow". This could be really huge. The last time, maybe the only other time, I saw this kind of completely uncapped, strongly unstable environment with the kinematics this system is forecast to have was May 4, 2003.* I'm majorly looking forward to tomorrow morning's data...if it confirms the NAM, we could be in for a monster day.

*Edit: That is, the last time I saw these conditions over such a large area was May 4th.

 

[Mikey Gribble]

I am torn between the west central into SW Oklahoma target and my original target up by Hays. With the new run storm motions are slower in OK, but SR low level winds are still better up by Hays. Aside from that, everything else is pretty much equal. I think both places are going to produce tornadoes tomorrow. I haven't really looked closely at other targets (I did glance over the DDC area).
There are several things that could be better, but everything you need is there for a tornado outbreak. CAPE and deep layer shear are more than adequate for supercells all along the dryline from Nebraska through Oklahoma. Low level shear is good enough for tornadic storms, 1km SR winds around 30kts and 5km SR winds >20kts. LCL's are low enough.
I think there will be several tornadic supercells coming off the dryline tomorrow and I also think a couple strong tornadoes will be possible anywhere between southern Oklahoma and southern Nebraska.
I think this is a pretty easy forecast, but it is a tough choice as far as a target goes. I honestly would probably target 50 miles South of Elk City Oklahoma strictly because of storm motions being slower. I think the tornado potential is equally good between that and the Hays target, but I am going to stick with Hays strictly because I chase for a station up here so I'm not going to head out of state unless I see more tornado potential and that isn't the case here. Both of those targets are a little ways out ahead of the dryline because I like to forecast until the last minute and then move in on the boundary. If anybody is heading to Hays there is a Super 8 with Wifi just South of one of the Hays exits off 70. I will be there unless I change my target tomorrow morning (which could very easily happen). I'm still waiting on WRF precip. graphics and morning observations. Good luck to everybody out there tomorrow. I think we are going to get our first big severe/tornado outbreak of 2007.

 

[Jay McCoy]

The NAM and GFS both backup the dryline quite a bit west into the central Tx Panhandle by 21z with SE winds @850mb at 30kts. 700mb swings to 200 degrees at 40kts and 500 is from SW at 60kts. CAPE is forecasted at 3000 in eastern panhandle. They will have to back the slight area back west some. the Mod (if they go there) will still be eastern part of panhandle. I love dryline days!!

 

[Bill Schintler]

Chase target for Wednesday, March 28

Chase target:
30 miles east of McCook, NE.

Timing:
4 PM CDT.

Storm mode:
While a severe threat obviously exists anywhere along the dryline from western KS, OK and into TX; the strongest shear and best hodographs will be coupled with adequate instability in southwestern NE near a developing triple point. An additional weakness with targets further south is that the orientation of the line of storms will be parallel to the flow both at the surface and aloft. A full spectrum of severe weather is possible, including a tornado threat.

Synopsis:
Evening UA analysis indicates deepening, neutrally tilted trough with a closed H5 circulation over NV. Strongest flow in excess of 100kts was found on the back side of the trough while maximum height falls were noted over CO. Previously closed H7 circulation that was over TX this morning has opened up into an open wave with an axis along northern KS into CO. Strengthening H7 trough was located from near Salt Lake City through SRN CA. Pronounced H7 ridge extended from a high in the SERN CONUS up into south central CAN. H85 low was centered over NWRN CO while a LLJ was slowly transporting moisture NWRD with an axis of 8C dewpoints nosing into NCNTRL NEB. At the surface, low pressure was located over WCNTRL CO while a diffuse WF extended along a GLD, HLC, HJH, to SDA line. A few areas of rain with embedded storms were located N of this boundary over ERN NE/WRN IA while dewpoints of 55F had worked into SCNTRL NE. The NAM initialized well to SFC and H85 moisture as well as precipitation trends but it was too strong with the H7flow over the PAC coast at the back of the primary trough. It initialized well to the H5 wind fields. The GFS was several degrees cool with SFC moisture.

Discussion:
SFC low pressure will be located over the North Platte by late afternoon while a triple point at the interface of a NW/SE oriented trough and an advancing DL will be located near McCook. In this area, MLCAPEs will exceed 1500J/kg beneath H5 temperatures of -15C. LCL heights should range from 800m to 1000m AGL with SFC dewpoints in the near 60F. Backed SFC flow coupled with SRLY 40kt flow a few thousand feet above the SFC will contribute to (SFC-3km) SRH’s of around 200m2/s2; while (SFC-6km) deep-layer shear will easily exceed 65kts beneath the exit region of a 75kt H5 streak.

[FONT=&quot]- bill[/FONT]

 

[Jeff Snyder]

(I'm on a cellphone connection still - which explains my silence in this thread, and the past week - since some AT&T/SBC DSL lines were cut nearby... So, this will be short since my forecast process has been abbreviated)
I agree with good potential south of I70. I like the shear profiles farther east of the dryline (in western OK), but I'm not sure storms will be in that environment until ~3z, given that the dryline is forecast to be located in the central and maybe eastern TX/OK panhandles. Shear profiles immediately along and ahead of the dryline aren't terribly impressive, though the zone of "unimpressive" low-level shear narrows as one heads northward towards I70. The forecast storm motions of 30-40kts south of KS and 40+kts north of there should result in storms that do develop along the dryline to move east of the dryline and into the better shear environment rather quickly.

I really like the less-backed mid- and upper-level flow on the latest NAM run, that's for sure. South of Kansas, 500mb and 250 is more out of the SW (rather than SSW), which is helping to veer the deep-layer shear vector and may help storm mode stay discrete (as opposed to QLCS). I have just come to hate days where the upper-level / anvil-level flow is nearly parallel (or less than 30 degrees from parallel) to the dryline or front. In my experiences, with those cases, seeding can reak havoc on storms (with anvil precipitation being advected from one storm to others along the dryline... next thing you know, you have boatloads of storm interactions and a developing squall line). In addition, I have come to hate environments with S-shaped hodographs, as I've been burned many more times than I've been rewarded in such environments. At any rate, mid-level forcing isn't particularly strong south of Kansas, with the mother-ship vort max will well to the warm sector. 700mb UVVs from the NAM show very strong, linearly-oriented forcing along the dryline north of the OK Panhandle, which again makes me suspicious of favorable storm mode up there. It's not worth getting too particular with local maxima in CAPE, SRH, and other parameters, since they can be extremely sensitive to minor fluctuations in Tds, sfc wind directions, and whatnot, all of which are difficult to nail-down (to 1-2 degrees F for the thermo parameters and/or 10-20 degrees for wind directions).

So, I'm aiming for extreme western or northwestern Oklahoma, knowing that the DL will by a couple/few counties to the west, giving me plenty of room to adjust N-S before the storms get into the better low-level shear environment east of the panhandles. Short-term climo (if that isn't entirely oxymoronic) tells me that, for whatever reason (voodoo or not), hedging towards Kansas seems to be a better bet than hedging towards southwestern Oklahoma or northwestern TX. Overall, I expect to see a long MDT risk from western NE down the dryline to western TX.

EDIT: I haven't looked at NE too much since I'm not hot on driving ~8+ hrs to a target that, I feel, isn't a whole lot better than a target 2-3 hours away from me. I'm sure there's a pretty decent tornado threat up in that area, but I'm not convinced it's worth the drive (nor am I convinced it'll be any more chaser-friendly than those the OK/TX area).

 

[afischer]

00Z GFS deepens the low- and especially mid-level cyclones slightly less than the NAM over the next 24 hours. This isn't unheard of, I guess. Luckily I don't see a big difference if the GFS ends up verifying, other than slightly weaker mid-and high-level flow tomorrow afternoon, and the dryline perhaps shaping up a little farther to the west.

Even more intriguing, a quick glance at the RAOB plots incidates that both the NAM and GFS significantly under-initialized the strength of the 500mb and especially the 300mb flow on the back side of the trough. OAK shows 150kt winds at 300mb, though the wind data ends abruptly right at this level so I'm slightly suspect of it. VBG though shows a 140kt vertical max just above 300mb though, so the OAK ob at 300mb may not be bad after all.

 

[Donald Giuliano]

I really like the less-backed mid- and upper-level flow on the latest NAM run, that's for sure. South of Kansas, 500mb and 250 is more out of the SW (rather than SSW), which is helping to veer the deep-layer shear vector and may help storm mode stay discrete (as opposed to QLCS). I have just come to hate days where the upper-level / anvil-level flow is nearly parallel (or less than 30 degrees from parallel) to the dryline or front. In my experiences, with those cases, seeding can reak havoc on storms (with anvil precipitation being advected from one storm to others along the dryline... next thing you know, you have boatloads of storm interactions and a developing squall line). In addition, I have come to hate environments with S-shaped hodographs, as I've been burned many more times than I've been rewarded in such environments.

Very good point about the S-shaped hodographs, Jeff. Though much less so around 00Z, the hodographs become quite S-shaped aloft by 03Z over much of the warm sector ahead of the dryline as the 300mb winds back. If nothing else, this could serve to limit the window of opportunity somewhat.

However, at the same time, I question why it is that this S-shape suddenly shows up at 03Z, and I think that it may be because the 300mb flow is being affected by convection in the model. By 03Z, the precipitation bullseye is in SW OK...west of the precip winds are SSW, east they are a tad west of SW, and downstream of the storms they are SW. Not to say this is the only thing going on, but it does appear to be having an impact.

Regardless, this is definitely something that bears watching given the size of the anvils these storms are likely to generate.

 

[Dustin Wilcox]

I like the looks of the 4km WRF which usally is pretty accurate, it does eventually have storms lining up across the area, but the first couple of hours after initiation it hints at supercells and even embeded supercells after dark. Basically tommorow I am going to try and find the overlap between the high intstability farther south and the more favorable shear farther to the North, right now I like the area around Holderage, but I will just head out west bound on 80 tomorow and evaluate things on the way. I'll be out there plenty early so if your gonna be in the area let me know and we can meet up and shoot the breeze.

 

[Matt Chatelain]

After looking at the models, I don't really see how the storms could go linear immediately. The hodographs seem to be classic for supercells. The 4Km wrf seems to fire supercells from central south dakota to the texas border. It even is hinting at supercells firing ahead of the dryline in western oklahoma. I am freaking out right now because I have a dynamics test at 4 PM and won't get out till 5:15, so I am hoping for those storms to fire ahead of the dryline which would be closer to norman. Good luck to everyone!

 

[Chris Wilburn]

I am really liking the western Oklahoma/eastern Texas panhandle and points to the south. It will be interesting to look at the models tomorrow and see if the forecasted CAPE and dewpoints hold up. Dewpoints are currently mid to upper 50's in this area. I expect some mixing to occur during the day so I hope we can get dewpoints to rise a little bit more before this happens. I hope the surface winds stay backed a bit and that the 500mb flow will veer to the sw. May need to go as far as the central Texas panhandle but that will be no problem as we are headed out early. Goal is to leave early and evaluated some more data on the road. I will take a look at the RUC in the morning along with soundings for the area. Will also try to keep track of where special soundings may be done. Of course will keep an eye on SPC's mesoanalysis page as well. We will try to get as far west as quickly as possible and go from there. I am chasing with Tyler Costantini and both of us or at least one of us will be on the spotter network, so stop by if you are in the area and we can shoot the breeze. We will be driving a 2005 Chevy Trailblazer. Good luck to all and hope to see a few of you out!

Chris Wilburn

 

[Jason A.C. Brock]

I have decided to moe my target of Woodward Oklahoma South to at least Altus but I may very well end up in Childress. It all kinda depends where the dryline is setup. I may very well as other mentioned try to stay back away from the dryline at least 30 miles to try to get a good angle at any incoming cells. Being there withing 10 miles of a forming supercell and seeing it mature is a tempting treat however. I will take another look at data before heading out and I may very well try to get to the target general area at least a couple hours before initiation if not more. That way I can keep an eye on data till the last minute and if something of a surprise looks to be occuring or not occuring I can still maybe have time to adjust positions if need be.
Im going to try not to overanalyze things and jsut get myself to the place where the storm forms and start photographing. All storms should be discrete and rather impressive initially and the further south one is I think the more discrete. In fact I kinda like the Childress option a little more due to its access to the South in Case things fire down towards Guthrie and Paducah Texas or just West of there. As always the Norman chasers seem to like the shamrock option for obvious reasons and the few Wichita Falls Chasers left here seem to like the Childress option again for obvious reasons. Both have good North South East and West Options for the msot part and both have Wifi spots. Dont get caught up in watching the radar in Wifi tho. Many chasers made that mistake with the Jayton tornado a couple years ago. Once a cell forms....go for it! I will try to pick anything Due West of jsut Southwest of me if it forms and works out that way. This may also be a long 2 days so get some sleep everyone and be safe. We all will have the chance at seeing some storms! Perhaps even some tornadoes. I tend to not get the hopes up too high for tornadoes until I see the video later that evening on the local news. I am also glad I enjoy alot more about storms than jsut tornadoes......but they certainly are a great added bonus.

OK MOTHER NATURE....BRING IT ON! IM ALL RAIN-Xed AND READY FOR ACTION! ;-)

Now I jsut have to force myself to SLEEEEP GRRRR

 

[BrandonWhittington]

Due to work restraints, I will be forced to focus and set my target close to home. Looking at all model runs and speaking with the NWS in AMA, I will try to stay in the Perryton, TX down to Canadian, TX, Beaver, OK and Shattuck, OK area. Skies have cleared out quit nicely here in Booker and I hope they stay that way. I will be driving my White Ford Explorer with Storm Search 7 on the side. Any one out there and see me, say hello, LOL...................Good luck to all.

 

[Tim Marshall]

TARGET: The eastern Texas Panhandle. TIME OF DEPARTURE: 10 AM. Ahh. Chasing in the ole stomping grounds again. This is a classic severe weather set-up. PROS - Deep trough moving out on the plains along with a dryline will encounter adequate low-level moisture. (I was afraid that yesterday's little short wave would have affected the moisture fields but it did not.) Expect supercells to develop along the dryline then move fairly quickly northeastward along the TX/OK border. CONS - The unidirectional flow aloft is a concern. We will need east-southeast winds at the surface to develop sufficient low-level shear and/or a right moving storm. Also, the lack of any visible mesoscale boundaries makes it difficult to come up with a focal point. So, it will be the old nut and shell game out there in a large area from western Nebraska to west Texas. TM