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4/29/04 FCST: OK/KS

Several months ago a had a "hunch" about the last two weeks of April being the time to watch out for storms. We had a lot of activity, but not much signficant output except needle tornadoes, straight-line wind damage, and some "near-nadoes."

This week the day with the best chances appears to be Thursday. We'll have good moisture returns on Tuesday (today) and Wenesday, and a LLJ will be in place to help the moisture and enhance the shear. The big variable IMO is the cold front that will be coming in from the NW. How fast will it move? How big will the temperature contrast be between the cold and warm air?

Will we have a strong and active dryline?

My best guess right now is W and SW of OKC and/or NW of Stillwater OK.

Well after looking at the 12Z ETA run. I have come to the conclusion that it will go linear quite quickly as they tend to do along a cold front. I was hoping, perhaps, things would look a little more descrete along the dryline but the lasted forecast sounding for FDR shows it to be linear as well, but it has a better chance of some embedded supercells. That would be my best guess as of right now.


Gfs look really good for Thursday afternoon in SW Oklahoma, perhaps near or just northwest of Lawton. LLJ lets better than last week, along with significant moisture return. Nice Shortwave to the west. Instability should be good. The only lacking factor will be a weak upper leve Jet. Supercells will be possible, with the potential for weak tornadoes. The system across the Ohio River Valley and Middle MS valley looks good on Saturday for a significant outbreak of Tornadoes
Again I see something very similar to last week... Instability should be decent Thurs and Friday. However, we're lacking decent mid-upper level flow. There may be shear for supercells, but again, shear looks weak for anything more than brief, weak tornadoes. Additionally, LCLs will likely be on the high side as dewpoints depressions are FORECAST to be near 15-20+ degrees. Ugh! Where are those high-shear spring systems?! Usually we see some high-shear, moderate instability days in April. So far, it seems like most of the chase days we've had have been with moderate instability (2000-3000 j/kg CAPE), but poor low-level shear. The best flow remains up in the northern US and Canada as the Gulf of Alaska low continues to churn away, as it has been for much of this spring. UVV images off the 12Z ETA does appear to suggest a potential for strong squall line development both Thursday and Friday. LCLs should be much better on Friday, but that's now getting into a different thread...
Quickly glancing through some of the forecasts for Thursday, I would venture to make wages on a squall line developing along the front. Moisture and instablility look good, but as its pointed out now (and likely will be in later runs), low level shear is looking less than good. Looks like another waste of a great wave! Hell, they're talking snow again here in Denver :roll: This system does have some good dynamics, though, so I'm likely to comment on this in later runs. Unfortunately, my chase time will be limited by school and work on Thursday, with a better chase chance (say that 10 times fast) Friday.. that's even further out.. maybe the front will hang around an extra day! :glasses8:
The GFS still has the low over the Four Corners by Thursday afternoon, so mid and upper-level winds will be fairly weak over the Southern Plains. I also wonder about moisture return as far north as Oklahoma, as we're still looking at mid to upper 50 dewpoints along the TX Gulf Coast today. Neither the GFS or the ETA indicate strong return flow between now and then.

Friday actually looks like the more interesting day, as the system finally ejects out into the Central Plains. The GFS seems a little quicker than the ETA (kind of funny considering it wanted to close it off in previous runs), shearing it out some in the process. With the front hanging around in N TX, something might happen, although I worry the core of upper level support will be too far north. The GFS indicates a chunk of energy swinging through to the south, however, so it bears watching.

Honestly, I'm not particularly excited about either day.
Wow, looking at the eta precip fcst in OK, Thurs. night into Friday looks to be a huge rain event. I think this is going to be a squall line b/c wind profiles look to be very linear, at least in OK. In NW tx it looks to be a little more favorable but still in question.
Chris is correct about the ETA-progged low-level shear. With an 850mb jet above most of OK, the 0-3k and 0-1k shear isn't too shabby. However, flow above that is pitiful -- <25kt 700mb and 25-30k 500mb.

It should be noted that the models are reallly not handling this system very consistently. One run, it's a cut-off over the 4-corners region through early Saturday; the next run it's an low that opens into a wave as it moves northeast, getting absorbed by the central US trough; the next run it's back to a lingering cutoff low in NM... The point it, neither the GFS nor the ETA are consistent here. IT does appear, however, that the ETA is coming more in line with the GFS, in that the low will not sit over NM, as it should open and shear northeastward into the central US trough. Whatever, the case, I'm hoping the GFS verifies, as, if it does, it looks like friday might be a chase day...

If GFS is correct. I still believe there could be a good threat for severe weather in eastern OK int SE KS and Norther Texas. It's forecast decent low level shear and mid-level flow of 40-50 kts. Moisture looks good, with Cape likely 3 to 4 thousand Joules. The eta, however, is less aggressive. It does not phase systems together, but is similar with frontal position and moisture return. I think it a little underdone with instability. Saturday could be a very big day in the Tenn and Ohio river valley. (not that anyone cares!) One more note. This could be it for a while. The weather pattern this spring has been very unusual to say the least. There's been very few watches issued this year. The upper jet seems to have dissappeared! Long range guidance continues to support this type of pattern right into the early part of May! Very depressing. Oh well, at least when there isn't big severe weather events, no one dies from tornadoes.
Re: gfs

Originally posted by Ken Johnson
There's been very few watches issued this year. The upper jet seems to have dissappeared!

It's appearing more and more like Thursday could have some severe storms, but deep-layer shear is quite weak for organized supercells. Instability is pretty good, however.

Ken makes an interesting point... At this time last year, there had been 178 watches issued. This year, however, 121 have been issued... That mean that we've had only about 2/3rds the number of watches this year compared to last.

SPC Watches issued through 4/28:
2004: 121
2003: 178
2002: 180
2001: 180
2000: ~220

(Numbers obtained via SPC Thunderstorm events page... they are probably not exact, but I'd say +- 2 watches... whatever the case, it makes my point)

**Yes, I know the number of watches are not an indication of how good or bad a chase year has been, but it is an indicator of how relatively quiet it has been nationally. This seems odd, seeing how I've never chased in March before this year, but this year I had 2 chases. Despite this, however, the southeastern US has been VERY quiet, and Texas has also been quite quiet...

P.S. -- I am starting to hold out hope for the end of next week... Latest GFS (lol you'd think I'd stop looking at day11 GFS output) has a nice trough digging from the west, which looks like it could produce a signficant outbreak. Now, if only we could ensure that the day11 (LOL) GFS verifies... BTW, I'm driving myself nuts looking at long-term model output...

P.P.S -- My apologies for the semi-off-topic post...
Maybe this is just my I-need-to-study-for-finals pessimism speaking, but I think that this is just going to be a huge grungefest. I don't think that the winds/shear are good enough to make it a huge event worth blowing off studying to go chase.
Well, I've already made plans for tomorrow (and the fact that I did so without even looking at tonight's model runs should tell you how much I thought of tomorrow's setup to begin with), so...

...you guys have fun chasing giant, long-track tornadoes.
Newbie here. Love this website.

I live in East Central Kansas, in the city of Lawrence.

I'm not too excited about today's setup. Tomorrow looks better, but might be south of my position.