3/30/06 FCST: IA/NE southward to central TX/LA

[bbarjenbruch]

Well... where to start???

First off, I must say that I am part of the Northern group of chasers, simply due to geographical position in Lincoln.

I'm worried about a couple of things up here. The first will be the stratus deck that is really going to make things problematic for both visual observation, and storm initiation. It seems, based on the 00Z NAM that there will be a dry punch capable of pushing this cloud deck off out of the way. The other dillema is whether or not the good wind dynamics will maintain far enough west in the clear slot. Another problem tomorrow will be the crazy storm speed. It's going to be really important to be in the right place at the right time as they are going to be hard (once again) to actually chase.

So where is the right place? It's hard to say right now, but I think my goal is to be sitting in York Nebraska (about right inbetween LNK and GRI) by 10 AM. This will depend largely on any ongoing convection, and the position of the cloud shield. A north or south repositioning may be advantageous as well in order to find the storms with a more easterly storm motion, feeling the helicity a bit more.

From then, the plan is to hang along the edge of the stratus, trying to pick off any discrete storms that develop and move toward the temperature gradient, and subsequent ambient vorticity, along said cloud boundary. With the low cloud tops (~30,000 ft), pronounced dry punch, and cold core low, it will be a fun "mini" supercell chase. The boundaries associated with early morning convection, old snowfall, and cloud shield will be very interesting as to how they add to this chase. Hopefully it will pan out with some rapid tornadogenesis, and a few damage-free touchdowns. Good luck to anyone venturing out tomorrow, whether North or South.

 

[Simon Brewer]

After taking a look at the 0z NAM I see a good possibility for a significant severe weather outbreak tomorrow with possibly a few long-track violent tornadoes!

Anywhere from Oklahoma to the Kansas/Nebraska border looks like fair game for tornadic supercells. I'm probably going to head up to Northern Kansas in the wee-early morning hours.

Late Note: for those looking for a cold core setup; this is not one of them, it is a classic setup for the warm sector east of the surface low.

 

[Scott Lincoln]

Anyone else notice the RUC model output putting the low pressure area in South Dakota... almost 300 miles north of the ETA/NAM output???

 

[Todd Rasmuson]

i'm making no final decision till about daybreak after reviewing surface charts,
latest data but attm i feel strongly in which could be wrong that the dryline wont
make it as far east as has been forecast its still way back there even tonight if
you put it in prospective so in reality we could be looking at a setup between i-44
and i-35 instead of along and east of i-35.. i feel pretty good areas anywhere
along and e of i-44 from nw tx to sw ok up through the okc metro to tulsa
could be in the line of fire... this could def be a *PDS* day esp once these
get a bit further east i-35 and points east i feel we could see one or two
long lived strong tornadoes... i'll have another post later tonight or
very early in the morning


Todd Rasmuson

 

[Donald Van Dyke]

Anyone else notice the RUC model output putting the low pressure area in South Dakota... almost 300 miles north of the ETA/NAM output???
[/b]

Actually, I don't think there is a particularly serious difference here. I think some of that is attributed the system initially getting organized east of the Rockies and the models trying to resolve where to stamp the "L" on the map. If you look at the 1000 mb contours off the RUC, NAM, and GFS, they're not terribly different. The NAM and GFS at 12Z tomorrow morning actually stamp two "L"s, but I would think the southern L will become the main area to follow as the system consolidates.

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...uc_slp_009l.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...fs_ten_012l.gif
http://www.nco.ncep.noaa.gov/pmb/nwprod/an...am_slp_012l.gif

Finally, I remember reading some years ago somewhere that the old NGM had a bias for initially developing lows east of the Rockies too far to the north, and look where the low is forecasted on the NGM tomorrow morning. There may a low there as forecasted, but it will not be the "main" low IMO.

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...gm_slp_012l.gif

The low "stamp" on the model is not as important initially IMO as the system is developing.

 

[Jeff Snyder]

From my blog...
The 0z NAM from this evening makes tomorrow look very appetizing! A very strong upper-level trough will eject out of the southwestern US tonight and tomorrow, leading to strong cyclogenesis in eastern Nebraska. The dryline will set up along the I35 by early afternoon, before marching eastward as a very intense vort max slams into central and eastern KS. Forcing from this feature (i.e. DPVA) will be weaker south of I40 in eastern OK (and northern TX). Shear profiles will be more than sufficient for supercells, and low-level shear (if the winds remained backed as the 0z NAM indicates) will be sufficient for strong tornadoes. The deeplayer shear vectors (which are progged to be >50kts east of the dryline) will be more normal to the dryline south of I40. I'm not sure that we'll see 65-68F Tds near the Red River as the NAM suggests, but we won't know that until morning. Almost all models overforecasted surface Tds
and kept surface flow too backed on 3/12, so I'm a little hesitant to accept this solution.

Currently, I'm favoring the area south of I40 and east of I35 in OK and northcentral/northeastern TX. Shear vector orientation relative to the dryline will be nearly normal here, which should favor discrete activity. Strong shear, as indicated above, will be more than sufficient for intense supercells, and mid-60 Tds (*crossing fingers*) should help boost CAPE to ~2000 j/kg. I'm afraid we'll see rapid squall line development north of Tulsa as intense mid-level UVVs push over the dryline in a strong DPVA regime ahead of the vort max. Farther south, the vort max trails west a bit and is a little weaker, so DPVA should also be a little weaker. NAM does show very strong UVVs along the dryline at 850mb by evening, so we may see squall line development farther south as well. However, I'll take my chances given the shear vector orientation relative to the dryline. In addition, NAM is forecasting Bunkers storm motions of 35-45kts south of I40, with 50-55kts north of I40 into eastern KS.

In the end, I think a lot of what happens tomorrow will depend upon what the surface winds do. If the winds can remained back, moisture will likely not mix out as much (i.e. Tds will remain elevated), and shear profiles will remain in the very strong category. In addition, backed flow in the warm sector will also help provide convergence on the dryline, which may be necessary for this southern target, which is more removed from the intense mid-level forcing that'll occur farther north. On the other hands, if winds veer a bit (such as what happened on 3/12), Tds will mix out a bit, low-level shear will weaken, and we could end up with a faster transition to squall line.

EDIT: Just noticed that there's a formatting issue w/ my blog in IE, but it works fine in Firefox.

 

[Kevin Polston]

Well....last night I did not think too much of the northern target area near the surface low because I thought there would be too much widespread precip. I re-evaluated looking at the 12Z Wed. models and it seemed like eastern Nebraska had a decent chance of seeing tornadic supercells. Now...looking at the 00Z ETA and GFS I think there is a very good chance of tornadic supercells near the surface low. Although both models are in good agreement with the placement of the surface low it is further south than what was shown even in the 12Z runs. What I like about this situation is a nice "dry punch" nosing from western Ok into northern KS.....which should help clear out the area just to the east of the low and dryline,; 0-3km cape values of 125-150 j/kg by 18Z just east of the low; strong lift from the approaching short wave trough, and when looking at the forecast soundings.....a nice "fat" cape profile with the EL about 300 mb. Also, LCL's and LFC's are in good shape with LCL's below 1000m just east of the dry punch, and LFC's roughly 1500 m. I believe it will be an early start in this area and as Rich T. said.....best to be out there early and don't hang back to the east too much. While it might not be the "classic" Davies cold core set up there are lots of similarities with the parameters that make it look very promising in my opinion. I believe it would be worth chasing (my only caveat being the ETA/NAM has sucked pretty bad lately - at least for events around KC that we were looking at - and the one thing which has me believing it more this time around is it is coming into pretty close agreement with the GFS. We'll see)

I still am standing by my forecast of my "southern area" from yesterday. I think Roger and Rich have the right idea in the MLC area late tomorrow afternoon. I still really like this area too and I think it could possibly extend down into far northeast TX. Although that is starting to get a little bit away from the upper system dynamics. Wherever the "tail end Charlie" sets up, whether it be in eastern OK or even down to the Red River....I think stands a very good chance of being tornadic. As of 06Z the plains are still quiet with no signs of any developing convection. Low 60's dewpoints have advanced into southern OK (although the station in far southeast Ok reporting 90/90 at 06Z seems a tad off!!). Profilers and VAD's showing 50-70 kt LLJ from OK into southern Nebraska so mositure should continue to advect northward. It will be interesting to see how these two areas play out later today.

 

[Chad Ringley]

Whoa nelly! 4.5 km WRF NMM has a few supercells in its little model domain

http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/

Esp. at 20 UTC..

http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/c...v2/refc_f20.gif

Note that its farther W than the current SPC 1 Day and the 00 UTC NAM I do believe.

If only we could make that reality tomorrow afternoon, huh?

Should point out that the 12 km WRF ARW which ran at 00 UTC should be out by morning as well. Interesting to see how it handles the various fields. I hate that the WRF NMM only produces precip graphics!!!!!

EDIT: Also, it's interesting how the discrete nature is picked up in this WRF fcst across OK, and clearly not so much in KS..which is consistent with the deep-layer shear forecasts from the 00 UTC NAM...forcing clearly more perpendicular to dryline in OK. That 06z SPC Convective Outlook makes me scratch my head a tad.....

 

[Todd Rasmuson]

ok guys i feel fairly good about things now dp temps flowing very well into
sc ok from n.tx latest from adm has 63 dp and all around ardmore is pretty much
in that range now as well through out sc/se ok therefore looking at all the data as
a whole and the pds day this could poss be, i strongly feel a large or maybe two
violent, long lived tornado could be poss i-35 ardmore to pauls valley,ok and points
east and points west of a durant to atoka oklahoma line.. within this area iam fairly
confident this area could be right in the bulls eye of some violent tornadoes later
today, i will post again later on but as the hours go along iam getting more and
more sure on this, also pretty sure we could see the mod risk moved a bit further
west in the next day 1 outlook later in the morning...


Todd Rasmuson

 

[brody_clifton]

Even though I still think the entire storm is still lacking the moisture of past systems under most of the intense deep layer shear areas.. I'm gonna go on a crazy assumption here that tonights 0330 00Z NAM run is right on the money on its 18hr and 24hr run:
Based solely on those two runs valid 18Z and 00Z tomorrow, one location in particular sticks out to me as having a great combination of favorable paramters for severe, along and near the KS/OK line about half way between I35 and the MO/AR border. In fact given all the parameters could even be a chance of a significant tornado should convection exist or develop near or in the area come very late afternoon/early evening tomorrow. Several positive factors, according to latest NAM run, will be present in the region during that time frame:
Under or very near the nose of a 10C (50F) 850mb moisture tongue, streaming up from even better moisture in south central OK. According to surface output, dryline will be setup through central KS/OK at noon (18z) and will surge eastward to the target area by 00Z. And dewpoints along the KS/OK border ahead of the dryline will reach or come very closeto 60F. So moisture and upward forcing from surface convergence just ahead of the dryline is there. The NAM shows this area as being on the tail end of a strong dry punch at 700mb, which is nosing newd into eastern KSat 00Z.
The NAM also shows an intersection of jets over the area at 00Z. At 18Z on the northwestern tip of a 50+ kt 850 mb low level jet, and on the western fringes of the jet as it grows even stronger and moves up into Missouri by 00Z. Under a 55-60kt 700mb jet max at 18Z and on the western edge of this max, centered in MO at over 60kt, at 00Z. A hundred miles east of the edge of a 75-80kt 500mb jet streak at 18Z and directly under the same 500mb wind max at 00Z. And on the northeastern nose of a 100+kt 250mb jet max pushing eastward into NE OK at 00Z, with a relative max in duffluence
at 250 mb over the area.
I strongly agree with others' feelings that areas down into OK look prime as well late tomorrow afternoon, going off the NAM's indication of surface DPs in the low to mid 60s. Assuming a squall line eastern KS/sern NE during afternoon/early eve, my NAM-based target should be far just enough away from the extreme upward forcing to have a chance at being discrete, perhaps a tail end chalie of the line.
But that's just going off tonight's NAM and it's prediction of the jet intersections over the nose of the moisture tongue at the same location. If I were really chasing tomorrow (darn that'd be nice) - looking primarily at the low level moisture/thetae fields already in place and predicted by late afternoon/earlyeve, I'd start somewhere near Ada, OK. And then kick myself if cells in SE KS remianed discrete during the late afternoon.

 

[Todd Rasmuson]

I truely believe its gonna poss turn out to be one heck of a chase day! rightnow at my place just n of adm
70 degrees at 2:00 am! dewpoint at 64... i just took note on the nws oun page under the 'enhanced weather page' a graphic was posted http://www.srh.noaa.gov/oun/enhancedwx/fxc...ows_Outlook.jpg for the dryline position for this afternoon they have also pulled it west kinda like i suspected would happen basically from a Enid,Ok to El Reno to Just W Of Chickasha to just E of Lawton to just E Of Wichita Falls. so i would bet in the future day one upcoming that we will see much more of central, sc, ok included into the mod risk area probley pushed back west a bit. I also stand by my strong wording earlyer in the eve that this could be a outbreak day, iam still kinda up in the air on exact targets for ok trying to take in to account several diffrent factors but non the less i'd basically say that sc ok area along i-35 adm to paulsvalley,ok poss up to the okc metro area and just e of there i'd say 'HIGH RISK' in my books for poss in that area of large, violent long lived tornadoes... these dp temp readings this early morning i must say are quite impressive, i didnt expect mid to upper 60s, thought at best we would have upper 50s to low 60s... so this is going quite well with good moisture return! we'll i'll add more of my 2 cents as the morning goes along but if anyone is still up let me know what ya think about my i-35 area from adm up to pauls valley,ok up to the okc metro.. i believe the
large tornado threat could be really close to these areas if not within and just e within say 30-40 miles east.

Todd Rasmuson

 

[Jeff Snyder]

Why am I not asleep yet? :roll:

Latest 6z RUC shows the dryline near Weatherford at 18z tomorrow, so I agree that the risk will prob be shifted a bit west. I'm curious as to why we haven't seen any elevated convection develop yet? All models, IIRC, had widespread elevated convection across most of OK and KS overnight, and so far, that hasn't happened. There are some showers trying to develop in western KS, but that's it. FWIW, the same RUC run shows CAPE ~2500 from far southern OK and ncentral TX (east of I44) by 18z, with significant 0-3km SRH east of there. I do think this will likely be at least a high-end MDT for central and eastern OK given the instability, shear, and convective mode likely being discrete supercells (at least longer than in KS). Comparing 0z NAM 6hr forecast to 6z RUC analysis, it appears that the upper trough out west may be a bit deeper than the NAM progged, so that may explain the slower trend / westward shift in the RUC and in the 12z-0z NAM runs. I still htink a LOT depends upon what happens in the next 8 hours in terms of elevated precip.

FWIW, I'm be a little cautious of the ASOS obs down near the Red River (and elsehwere in OK for that matter). Some obs (Ardmore in particular) tend to be 2-5F higher in dewpoint than nearby OK Mesonet obs. I think I trust the Mesonet data more, so just keep that in mind. The real (>65F td) juice remains locked in deep south TX, but there is an uninterrupted source of >60F Tds from I40 to the Gulf coast. I expect to see 61-63F tds tomorrow, since most of central and northern TX is currently seeing that. Vici and Haviland KS profilers showing 65kts off the surface, which is helping transport that moisture. In addition, sfc winds in western OK remain ~30mph sustained (at 2am nonetheless!).

 

[Matthew Havin]

Target as of 2 AM Thu: A box from Wichita-Chanute-Arkansas City-Coffeyville (KS)

As of 2 AM, southern surface low between Limon and Burlington CO at 997mb.
1500 SBCape has now moved into Woodward, OK and sneaking into SW KS east of Liberal.

6Z NAM has sfc low progged to move to NC KS by 21Z. Precip looks to break out just east of the low in NC KS and SE NE anytime after 18Z today. Warm and unstable air in my target area will likely see 70F+ and 1500-2000+ CAPE by 21Z if morning elevated precip doesn't interfere too much, with firing of cells around this time. Do a 21Z sounding of CNU and you'll catch my drift. This area will be under some strong surface winds by afternoon, with 25-30 MPH with gusts to 35-40+. Winds look to be from SSE under the NAM. Low LFCs will also aid tornado potential, with the LFC at or less than 700-900 meters from the surface at afternoon.

Any cells south of this target area that fire with daylight will likely see an even better scenario, with slower storm cells, better wind regime, and better instability (as Rich mentioned before). However, since I don't live in OK, we are planning on going for the target above due to daylight concerns.

EDIT: 335 AM Wichita AFD echo close thoughts.... http://iwin.nws.noaa.gov/iwin/ks/discussion.html

 

[Bill Tabor]

Looks like the Big Dog is about to Bark! I think the southern area / dryline looks strong. Dewpoints are showing better than previous model runs. With heating after initial convection - even stronger. Appears to me possibility of a few strong tornadoes possibly even a violent one. IMO likely small to moderate outbreak. Best guess SPC goes moderate with sig torn hatching possibly high risk in area of higher instabilities combined with outflow boundary left over from overnight convection.

Will I make it to the show? Maybe :wacko:

Good luck tomorrow - eh later today! I better get some rest.

 

[Paul Knightley]

Us chasers "across the pond" like to "virtual chase" these set-ups, in order to practice before coming over in May! My initial target is likely to be somewhere in the Salina - Topeka corridor - perhaps a little SE of there. Looks like some backed surface flow may continue there, as well as the fairly narrow instability axis progged by various models.