5/1/08 FCST: KS/MO/OK/AR/TX/NE/IA

[Mike Hollingshead]

Well I mostly meant it's a lot easier to get dews to increase a little at night, with loss of heating. 60 sfc TD in se KS at 6 a.m. likely wouldn't tell me all that much.

And wasn't the ruc's biggest issue with some moisture deal? It should still do decent or well with the amount of winds, and yes, they are pretty impressive all night long. Zoom zoom moisture.

 

[mark plate]

Yeah hoping for moisture as far north as central IA seems at this point a little loopy! But as for shear, dereks right its good until you get up to around 500mb then it is just weak to say the least. Not sure if that profile would be enough given there was any moisture? Looks good though if things could speed up a bit!

Hard to play this one out! I guess we will just have to see how far the moisture will get by around 00z friday.

Ohhh yeah and I forgot to mention gas is up to 3.70, LOL. Not fun for me I live in IN. And if I see any miracles in the moisture department I will be on the move again like always! Talk about an expense I envy all of you who complain about driving say as far as central OK from KC

Dewpoints will be as high along the warm front as they will be in SE KS...15-17C...as forecast by the normally most reliable models. 500 winds are only weak on the GFS/WRF-NAM...not exactly the best models around. Much better on the normally more reliable UKMET/ECMWF...still only 30 knots, but that's just enough.

 

[Darrin Rasberry]

We're getting some decent helicity and CAPE up here in Iowa (not Ames, but more to the SW part of the state). GFS is pushing some nice-looking SE winds, and the upper-level winds at least don't look as bad as they did before. KDMX is pushing 60% or so on supercell potential, but with ML LCLs in the 600's I'm not quite sure how to interpret that with my newbie skills. I'm sure the ML LCLs will be higher to the SW part of Iowa, off-model runs are guessing around 800m for the area.

Earl's page maze is showing some decent shear and storm-relatives for SW Iowa now, and at 21Z tomorrow the dews are looking to be in the upper 50's ... with temps in the lower 60's.

-Winds are good until the aforementioned somewhat weak (but as per the model progression, increasing) upper-levels.

-Moisture better get here. With the strong southerly push illustrated by Mike H above it just might happen.

-SB CAPE and 0-1km CAPE look great.

-Getting some shear and helicity for that area.

-Winds look to back a bit more for SW Iowa, at least at the surface.

-Cap projected to erode a bit better than the southern target.

-Actually, it's NW Missouri that looks the best to me right now, but I don't want to chase there in the 15th century, where I can't pick up any signals, but I will if I have to.

-Looking for initiation up here, around 5 PM or so.

I put the likelihood at something happening for us far-northerners at a 1 in 3 shot.

As far as the southern target goes, it's been said earlier in the thread, and it's something I've said way too much this year: either there's going to be nothing or there's going to be one or two very destructive supercells.

It all depends on the moisture. Blow, winds, blow.

 

[mark plate]

We're getting some decent helicity and CAPE up here in Iowa (not Ames, but more to the SW part of the state). GFS is pushing some nice-looking SE winds, and the upper-level winds at least don't look as bad as they did before. KDMX is pushing 60% or so on supercell potential, but with ML LCLs in the 600's I'm not quite sure how to interpret that with my newbie skills. I'm sure the ML LCLs will be higher to the SW part of Iowa, off-model runs are guessing around 800m for the area.

SW Iowa is as much or more a longshot than the southern target. They're easily within the warm sector and will be much warmer than the lower 60s late tomorrow afternoon...likely near 80. But the same problem exists there as exists to the south. Storms may never occur in SW Iowa...at least the southern target will see a storm...it just might be after midnight...

The better bet up there is near your location of Ames or even a bit north of there...along the warm front.

 

[Darrin Rasberry]

I'm not showing 70's on the WRF, more of upper 60's, but that may be a bit optimistic ... as well as dews in the lower 60's at 21/00z from this model. But the warm front does appear to be just north of Ames at 00z. The 500mb winds start to pick up a bit after 00, I wonder how much and when. Cape is okay. Observing the setup, I wouldn't sit on my buttski here in Ames, but would prefer to head out west toward the Jefferson area where I took those blurry images last Thursday. Perhaps I can catch some daytime initiation there, maybe a tad south along I-80 west of Des Moines approaching the Council Bluffs area. Thanks for the heads-up on that.

 

[Derek Weston]

SW Iowa is as much or more a longshot than the southern target. They're easily within the warm sector and will be much warmer than the lower 60s late tomorrow afternoon...likely near 80. But the same problem exists there as exists to the south. Storms may never occur in SW Iowa...at least the southern target will see a storm...it just might be after midnight...

The better bet up there is near your location of Ames or even a bit north of there...along the warm front.

Cap. An issue on the NAM. Does the model you're going by have this issue?

Do you have a link to the model (ECMWF) that you've been using for your call on this one? I'm just not seeing what you're seeing...

 

[Darrin Rasberry]

Cap. An issue on the NAM. Does the model you're going by have this issue?

Do you have a link to the model (ECMWF) that you've been using for your call on this one? I'm just not seeing what you're seeing...

CIN to the west of DMX around the Council Bluffs area will have the best chance to weaken the quickest with daytime still around. Cap's gone by 06z, may be a night event but I'll take what I can get.

 

[Mikey Gribble]

The cap looks to be a pretty serious issue with the 00Z NAM. I will still be chasing regardless, but I am starting to doubt the cap will break. Dewpoints in the mid 60's are onshore and should make it to the target area by 22Z. I am thinking dewpoints in the 62-65 range are reasonable across northern Oklahoma and far southern Kansas.
My target is Ponca City by 4PM. Best of luck to anybody chasing. Be sure to bring the football because we may be waiting around a while.
BTW I didn't look at it tonight, but the boundary intersection may be a safer bet. I will look at it in the morning, but I will probably still chase the dryline in northern Oklahoma.

 

[Mike Hollingshead]

Anyone have any clue what type of sfc low pattern we'll actually have tomorrow? This is enough to drive me nuts. Nam looks a little nuts. Looks like it wants to break it up into different areas of lower pressure, with a surging cold front, then lets up on the surging cold front. It just looks troubled from 18-6z.

http://www.rap.ucar.edu/weather/model/displayMod.php?var=eta_sfc_mslp&hours=hr18hr24hr30

If we wind up with something more like the extended ruc says, it changes everything up here.

http://ruc.noaa.gov/disp2.cgi?/w3/rapb/plots_13km_dev/.//+dewpt+am+24

That makes more sense to me. I'd likely chase very close to here if that's how it pans out. The ECMWF and UKMET both seemed to have a look more like that. Sigh. Just such a difference maker in targeting, and at this rate it's not going to be clear till what, 6 hours before you have to be there? Guess that'd be enough.

 

[mark plate]

Cap. An issue on the NAM. Does the model you're going by have this issue?

Do you have a link to the model (ECMWF) that you've been using for your call on this one? I'm just not seeing what you're seeing...

Cap is an issue everywhere...I only said that northern or central Iowa may be a "sleeper", not that I'm convinced much will happen there either. I think the cap has every bit as much or more chance to break in the northern half of Iowa along the warm front as it does in the warm sector during daylight hours. I'm not really calling anything just saying don't be surprised if something happens up there and nothing happens further south (during daylight).

The WRF (NAM) is my least favorite model (other than the NGM) mainly because it's the least accurate...at least in my part of the country. I look at the ECMWF and UKMET on AWIPS...no real good links to them online that I know of. Of interest though is that the 00Z WRF (NAM) now also has 30 knot 500 winds in Iowa at 00Z...quite a change from its 18Z run and more in line with the European models.

 

[Van DeWald]

After looking at the Nam, still think there might be cap issues until 06z-09z for the OK targets. I was previously targeting the OK/KS border yesterday evening, but may shift a bit further north, near Emporia, KS.

24hour Nam sounding:
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=024&STATIONID=kemp

That may be the tail end of the convection and the best combination of low level shear in the 00z-03z time frame. Parameters just go nuts there, with a 0-1km EHI of +12, a 0-1km SRH of 547, a VGP of 1.4 and an LCL of 700m (plan view maps) How cool is that?

I have no doubt the front will fire further south in OK, but not until very late.

Am also thinking that the SPC will be upgrading to a moderate risk. ** Edit, still not sure about this, they may just go slight given uncertainties that still exist.

 

[Mikey Gribble]

I agree with the last post. The environment near and either side of Wichita goes nuts in the 00Z-03Z time frame. Shifting North a ways will likely be the smart play tomorrow. I am definitely going to be considering it, but I don't want to do any more forecasting tonight so I will figure it out in the morning. I may just play this one from home until 4PM or so considering that the most favorable environment for tornadoes after 00Z is pretty much over my apartment.

 

[Donald Giuliano]

I've been really concerned about tomorrow due to the possibility of mediocre moisture return, but this problem may be rapidly fading. Based on VWP observations, winds around 1 km AGL are currently running from a minimum of 40-50 kt in Brownsville to a maximum of 80 kt in northern OK/southern KS. Based on the 00Z Brownsville sounding and the likelihood that even better moisture was lurking just offshore to the south-southeast, I think mid-60s ahead of the dryline are a good bet, with upper 60s a distinct possibility. Tomorrow's 12Z soundings will pretty much tell the tale.

Now timing of initiation could be an issue when it comes to daytime action, as noted by many, but that's another story altogether...though at least the 700 mb CAA seems to have kicked in pretty well by 00Z.

 

[Dick McGowan]

After looking at the Nam, still think there might be cap issues until 06z-09z for the OK targets. I was previously targeting the OK/KS border yesterday evening, but may shift a bit further north, near Emporia, KS.

24hour Nam sounding:
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=024&STATIONID=kemp

Quite the difference with the GFS:

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

(the site might go down) LCL -990
LFC -2000
MLCINH- -48
CINH - -119

Everything else looks great.

 

[Bill Schintler]

Chase Target for Thursday, May 1

Chase target:
Lebo, KS (22 miles east of Emporia).

Timing and storm mode:
Storm initiation will be at 7:30 PM CDT. During the early evening hours, supercell storms will be capable of a tornado or two. Later in the evening, a transition to a linear convective mode will take place.

Synopsis:
An ULVL S/WV will translate across the CNTRL Rockies overnight. Over the next 12 hours, a H5 height fall bulls eye track from ERN CO into WRN KS. SFC cyclogenesis will take place in response to this over KS and NEB with impressive NWRD moisture transport. A look at SFC observations across the WRN GULF and SRN TX indicate a gradual air mass modification is underway with an axis of low- to middle-60 dewpoints along I-35 and S of the Red River. A ST deck will develop by morning in areas E of I35 in KS and over much of NEB near the nose of a 70kt LLJ and isentropic lift. SFC dewpoints in MO and KS are verifying several degrees lower then WRF and to a lesser extent GFS PROGS.

Discussion:
A potentially significant SVR event is possible, however there are a few mitigating factors, most important of which are the extent of SFC moisture return and capping strength. Timing of forcing is also a concern. The ULVL cyclone will progress slowly to the E into WRN NEB during the period while a 60kt H5 streak rounds the trough base. An associated SFC low will take its time while tracking to the NE into SWRN IA by 06Z Friday. A WF extending E of this feature will strengthen and approach the IA/MN border late in the period. Meanwhile, a trailing CF will track E into KS and OK while overtaking a DL in ERN KS. The vicinity of this CF/DL triple point appears to be the most likely location for SFC-based convection within a moderately capped environment. Further S along the DL in SRN KS through TX, large-scale subsidence should exist in the right-exit region of the cyclonic H5 flow.

During the afternoon hours, a ST deck will erode and give way to a CU field within the warm sector in extreme NERN OK, ERN KS, and much of NEB. H85 flow will gradually back throughout the day as low pressure strengthens in CNTRL NEB. An area of broken CI, a harbinger of the stronger ULVL forcing and diffluence, will reach the I35/I135 area in CNTRL KS by 00Z. Strong capping will persist until 23Z when mid-level temperatures begin to cool several degrees as the ULVL system starts to overspread the area. MDLs seem to be overestimating SFC moisture to some degree. Considering the trajectory of moisture currently over NRN TX and anticipated LLVL fields, a duration of 20 hours would be required for transport of the moisture into the target area assuming that no mixing occurs. This is overly optimistic as strong SFC heating will result in considerable mixing of the skin-deep moisture. An axis of 60-63F dewpoints in ERN KS ahead of the DL/CF seems more reasonable and is supported by the SREF. MLCAPEs of 1500 - 2000J/kg should exist beneath mid-level lapse rates of 8-8.5 C/km.

The most favorable dynamics and shear parameters will hold off until 03Z. Veering SFC flow will lead to small hodograph curvatures until the mid-evening hours when a SWRLY LLJ increases to 60kts. Deep layer shear AOA 50kts will overspread the area after 04Z with the EWRD progression of the strongest H5 flow. A narrow opportunity for tornadogenesis should exist as the BL begins to decouple and LLVL directional shear increases.

- bill
11:10 PM CDT, 04/30/08