David C Watson
Has anyone bothered to look at the upper level wind data for the 6th and the 7th? I think there is a legitimate shot at a decent day. What does anyone else think or am I just seeing things?
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Skip Talbot
EF5
Its nice to see the GFS showing a trough at that time range for the past few runs. That's going to be only half the picture though. Moisture return looks to be enough, but with the warm UA temps, the diffuse dryline and low 60's dews might not cut it. I can't get excited at this time range, but if the trough is still there two or three days from now, and the GFS is plotting something higher than 1000 J/Kg, I"ll start giving it a more serious look.
David C Watson
As far as the latest GFS run is concerned it still looks good but the day is getting more and more pushed back now. It looks more like the 8th or 9th possibly now.. Dew points are in the mid 60s which is great. Surface winds are pretty impressive out of the southeast as well. The dry line still looks really iffy attm right now. I think given the strength of the trough and the quality of the moisture, should warrant at least a slight risk of some severe storms but then again, I would hold off due to the lack of CAPE. That's just my personal opinion right now.
David C Watson
And then I see that there will be a closed low over OK with good CAPE on the 10th. I don't know if the GFS is just throwing garbage out there or it's possibly going to be the real deal, but this should be pretty interesting coming up pretty soon. Definitely something worth watching now in my eyes..
David C Watson
Latest GFS model is still showing a pretty impressive short-wave trough ejecting through the Pacific Northwest and going all the way down the train tracks of the jet stream express and right into OK. CAPE values are slowly creeping up on this run and the quality of the moisture isn't as great as last nights run but made up for the lack of CAPE.
Skip Talbot
EF5
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The GFS has a tendency to be too fast, and we're definitely seeing the arrival of this system slow down from run to run on the GFS. This is a great reason why we typically hold off making severe weather forecasts for particular days until the forecast event is less than a week out from when the forecast was created. There is just too much uncertainty beyond that point.
Specific values for CAPE at that range are almost worthless. I wouldn't read too much into that until we're in the day 5-6 range or sooner.
Warm midlevels:
http://www.twisterdata.com/data/mod...9/29/12/GFS_3_2011092912_F180_TMPC_500_MB.png
poor lapse rates, and rather marginal moisture for this time of year may very well doom any chase setup, despite the impressive trough. I wouldn't turn my back on a trough like that, but at face value this system looks a non event except for maybe isolated severe weather in the southern plains. Of course it could change radically at this time range (for better or worse).
The GFS has a tendency to be too fast, and we're definitely seeing the arrival of this system slow down from run to run on the GFS. This is a great reason why we typically hold off making severe weather forecasts for particular days until the forecast event is less than a week out from when the forecast was created. There is just too much uncertainty beyond that point.
Specific values for CAPE at that range are almost worthless. I wouldn't read too much into that until we're in the day 5-6 range or sooner.
Warm midlevels:
http://www.twisterdata.com/data/mod...9/29/12/GFS_3_2011092912_F180_TMPC_500_MB.png
poor lapse rates, and rather marginal moisture for this time of year may very well doom any chase setup, despite the impressive trough. I wouldn't turn my back on a trough like that, but at face value this system looks a non event except for maybe isolated severe weather in the southern plains. Of course it could change radically at this time range (for better or worse).
Brett Roberts
EF5
I've learned my lesson with fall setups over my six years of chasing thus far: good moisture or bust. I have never seen a tornado or had a truly rewarding chase in October or November, and virtually every time the culprit was meager moisture and instability. Furthermore, when I looked back at some of the memorable fall chase days from before my time (like 2001-10-09 and 1998-10-04), I noticed they were characterized by ~68-70 F dew points in the most unstable part of the warm sector. This is usually necessary to compensate for autumn's generally-poor lapse rates.
With next week's trough, I'm not seeing any indication of exceptional moisture return, and that's what it will take to get me excited about discrete tornadic supercells in the Plains this time of year. Severe weather may well occur, but I'd try to keep your expectations in check (which I know is easier said than done after 3-4 months of nonstop dryness; believe me).
With next week's trough, I'm not seeing any indication of exceptional moisture return, and that's what it will take to get me excited about discrete tornadic supercells in the Plains this time of year. Severe weather may well occur, but I'd try to keep your expectations in check (which I know is easier said than done after 3-4 months of nonstop dryness; believe me).
Patrick Marsh
EF5
- Joined
- Apr 18, 2006
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One reason for your busts, Brett, is that in the fall we are typically dealing with slightly warmer mid-levels due to the warm season ridges and/or weaker lapse rates due to the warm season repeated convection. Thus you need better low-level moisture for stronger instability to offset the weaker mid-level lapse rates.
Looks like the 12Z runs this morning from the FIM and GFS are beginning to agree with the ECMWF's consistent prediction that the trough will cut off and stall over the SW. Thus mid-level flow weakens and it appears that a widespread severe weather event is less likely. Granted, this is still 150+ hours out, so things can still change. Even if this trough does not spawn a severe weather event, it is a full-blown Pacific trough and as such will bring a lot of moisture to the drough-stricken areas of the SW US and the SGP. Could be a nice soaking for parts of TX and OK.
David C Watson
I still have a hope that there could be a localized severe weather event..
David C Watson
The only thing that really needs to change is that there needs to be cooler mid-level temps, better moisture (even though 60+ dews are nice), and better CAPE values 1500+ J/KG.
I'm thinking the reason why the instability is lacking is cause there will likely be a lot of cloud cover. If we don't get even a localized severe event, at least we will get some much needed rain..
I'm thinking the reason why the instability is lacking is cause there will likely be a lot of cloud cover. If we don't get even a localized severe event, at least we will get some much needed rain..
David C Watson
The 700mb UA temps are still pretty warm and instability is really poor with the latest model guidance. I think the way this is going, it will be more of a general rain/thunderstorm event other than a severe weather event at the moment..
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