2014-05-10 FCST: OK, KS, MO

[chrisbray]

After today's system quickly leaves the area, moist and unstable conditions appear set to return on Saturday. Latest NAM/NAM 4km seem sure that some storms are going to form in the KS/MO area despite the relative lack of forcing mechanisms. CAPE looks to be pretty big, up to 3000 MLcape, with surface winds ranging from just west of south, to just east of south as you move east into Missouri. Shear isn't terribly strong, appearing to top out around 40 knots, but the directional shear seems decent. Enough for a tornado or two on storms that fire? My friend and I are sure hoping so. We start a two day chase into western Missouri tomorrow!

 

[Taylor Wright]

I'll take a stab at this one since it's close by. NAM and GFS have backed winds in the northern half of Missouri with dews pushing into the 70s mid-day. The NAM has the dryline moving east a bit throughout the day, perhaps enough to serve as a lifting mechanism. Looks like CAPE shouldn't have a problem getting above 3000 J. Low-level shear is sufficient, hodos are nice, sfc-500 mb crossovers greater than 100 degrees. Definitely worth an hour or two drive to north-central MO if the NAM verifies. As Chris said, shear could be better, but looks as though it should be above 40 kts. Any isolated supercells that develop should definitely have tornado potential tomorrow. I'm not a huge fan of the terrain over there, but by now I'm used to it. We'll see how it looks in the morning, but as of right now I'm in.

 

[Taylor Wright]

Quoting NWS forecasts is not how you are supposed make a forecast on here, but I appreciate you at least telling me why you disagreed with me. Keep in mind Topeka is much farther west than Mo where LCLs are much higher. Dewpoints are likely overdone, I agree. However, they shouldn't have a problem reaching above 60 degrees in some areas (yes, 70 degrees was a little much). Model disagreement is a factor with the GFS showing much lower tornado potential, but the NAM has been winning out lately from what I've noticed, but I could be wrong about that, as I've mainly just been paying attention to models the day of lately. Overall, low level shear isn't great, but the last few NAM runs has small areas of decent 0-1 km helicity somewhere in Missouri.

http://www.twisterdata.com/index.php?prog=forecast&model=NAM&grid=221&model_yyyy=2014&model_mm=05&model_dd=10&model_init_hh=00&fhour=24&parameter=HLCY&level=1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND&unit=none&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false

Both the NAM and GFS have LCLs lower than 1000 m in MO, as well.

Looking at the latest RAP, which only goes out to 1 pm tomorrow, it doesn't appear moisture will advect as far north as the NAM and GFS have forecast, so who knows about moisture really. Lost lot of hope in this. Probably will end up being too low and throwing the whole setup out. My previous forecast was weighed heavily on the NAM solution before I could look at the RAP. I'm not as experienced as others at determining whether or not the models are overdoing moisture, but it seemed like the system that just went through didn't totally wipe it out, and it is May. This could be within 100 miles of me, so if there's even a small chance I'll probably be on it.

 

[Will Campbell]

Tomorrow looks to be a quite marginal day. While I agree the models have been murdering moisture this year, I think they may have a better handle over the next couple days. The NAM and GFS both put the 40 Td mark laying across KC and SW/NE from there. Current obs have near 50 Tds as far north as St. Joe, MO. Now taken at face value if the moisture conveyor can bring mid 60+ Tds to northern MO I think acceptable LCLs will be there but they are substantially higher along the river to the west, as highs are progged around 85 for most of northern MO and slightly higher with western extent. With that being said the area is slightly baroclinic, but will it be enough to provide a forcing mechanism for a surface particle? With pretty meager H5 flow at 0z as evidenced by the NAM with 35kts and slightly higher with the GFS being closer to 40kts, there will be some upper level divergence. CAPE will be maximized around and east of the KC metro with nearly 3000 J/Kg, and just east of the river there looks to be bulk shear available to the order of 40-50 kts. Winds back with time slightly in MO but there is a fairly stout inversion evidenced by all outputs I have looked at, as well as the veer back veer wind profile. If a storm can get going and remain organized, I wouldn't rule out a window for tornadic potential as it moves ENE into better moisture.

Ultimately it feels like a true coinflip/2% sort of day. Since I will be out Sunday and foregoing Mother's Day festivities, I will likely sit this out to satiate the paternal need of the mother and keep a keen eye on Sunday, and wish all that venture out tomorrow the best of luck.

 

[Taylor Wright]

I wish I knew why the RAP differed so much from the NAM and GFS with regards to moisture and instability. Does anyone care to offer insight on that? The SPC seems to be leaning toward the NAM solution given their tornado probs are higher than what I expected. Both the NAM and RAP agree on a small area of increased 0-1 km helicity up to 150 east of the St. Jo and KCMO area during the afternoon. HRRR has cells firing off as early as 3 pm in that area. Winds are backed, but hodos are messy and low-level speed shear is pretty weak with 850 mb winds struggling to get up to 25 kts. Definitely a long shot at seeing a tornado, but I always appreciate a challenge. I wouldn't be surprised if the SPC drops this to a 2% risk on the next outlook given how weak the low-level jet is. Also, LCLs could be an issue if moisture struggles like the RAP is showing. If we can get dews into the 60s and the low-level jet is a little stronger than what is forcast, I think my chances will increase a little bit. I can't chase tomorrow, so this might be my last shot at getting another tornado this year if a blocking pattern sets up in June. I'll be happy with some structure shots, though, if not.

 

[rdale]

The RAP has a known bug that often makes it horrible trying to use in low level moisture situations. This is from the developer: In Response To: RAP 2M issues? (Rob Dale)
Hi Rob, thanks for your email on RAPv2 2m biases and the link for the Iowa State website. We agree that there still is some 2m warm bias in daytime with RAPv2 but think it is clearly better overall than RAPv1. There is more RAPv2 2m info in a Feb 2014 NWS webinar at http://ruc.noaa.gov/pdf/RAPv2-NWSwebinar-18feb2014-FINAL.pdf, and I also just put together a little recent look at RAPv2 and RAPv3 surface verification at http://ruc.noaa.gov/pdf/RAPv2-temp-dewpoint-verif-Apr2014.pdf. Thanks again and please post again and feel free to add RAPv3 and HRRR to your watch list. Stan B.