Active pattern coming up

[Jeff Duda]

Looking to pump up the weather related posts here in the off-season. I had noticed a big-time open wave flying across the SGP late next week in the GFS. Although the nature of that system has shifted around, the GFS, and now the FIM and ECMWF are on board with this system, although still varying in the timing. There are thermodynamic issues with this system in terms of causing a severe weather event, but the cool thing to see for the drought-stricken south-central US is the passage of several big shortwaves in the medium-range period. These systems all look to have decent moisture with them and some pleasant QPFs are coming out of this. This seems to be a pattern that will help states like TX, OK, and KS really start to rebound from this massive drought. I doubt this pattern will fully eliminate it, but it may drop a large portion of D4 areas down to D3 or D2. After all, the 3"-4" that fell in C OK at the beginning of October helped drop some of those statuses to D3 (http://droughtmonitor.unl.edu/DM_state.htm?OK,S). What do others think on this active pattern setting up?

 

[CGardner]

I was just talking about that to my chaser buddy in Fort Smith. The shortwave trough coming through that area on Wednesday/Thursday should bring some good moisture to the areas. I think the key area is the Red River valley area of TX and OK, for any convection. If this keeps the strength as the models show it through this next week, Sat will be very interesting in East Texas, OK, and Texarkana area, that is if the supposed warm boundary pushes up from the Gulf like they say it will.

 

[Chip Redmond]

Models in fairly good agreement with the next several systems. Low that will develop on Tuesday looks as if it will track a bit farther north than the last with the GFS and GEM, but EMCWF takes it south a bit more with a deeper trough. Euro has been better as of late and would expect this system to follow it and graze the panhandles.

As for the weekend system, however it ends up, it will likely be a dandy with a high amplitude trough ejecting over the Rookies. Models agreeing that it greatly deepen on Saturday but placement is an obvious issue. All models but the GFS have been trending farther west and not as far south with the system. With cold temps and a tight gradient, near blizzard conditions could definitely be possible for the up here in the great state of South Dakota. Both Euro and GEM agree with this system and have bulk of trowal precip falling in the Dakotas. GFS is a bit farther east and slower. With the kind of flow over the conus the past month, I think the models may be a bit bullish with this system and it will weaken with it through the week. However, they have been keeping up with this for quite a few runs now. Trend farther west and north though supports a weaker system. Moisture return off the Gulf is nearly non-existant with perhaps a marginal chance at a thunderstorm or two for southern OK into TX Saturday.

Looks like the best show for Texas rain would come with an early next week system that develops from the Gulf. It is pretty far out, but still pends some watching.

Definitely a few things to watch! I agree, lets get some weather talk going! Anyone going to do a few chase cases this year?

Chip

 

[Jesse Risley]

In addition to this week's system, both the GFS and the ECMWF are picking up on another storm in the middle of next week per the 12z runs from earlier today. Obviously timing and placement issues exist this far out, but it looks like another potent trough comes ashore early next week, with a respectable low pressure system kicking out of the Southern Plains and moving towards southern Lake Michigan, at least as currently depicted at 200 hrs out.

 

[Mike Smith]

Yes, perhaps the drought is going to be dented by the time November 15 arrives. Welcome moisture.

 

[CGardner]

Well, here we go boys! SPC came out this morning and issued severe threats on the convective outlook for days 5-6 for most of Oklahoma. The trough that is coming from the Pacific NW is I guess getting stalled by the ridge right over the plains. They are saying Monday and Tuesday will have good potential for diurunal supercells with large hail, damaging winds, and a "few" tornadoes. Once again, my work places me in the best possible spot at the best possible times.

See you all there!

 

[Jesse Risley]

Well, here we go boys! SPC came out this morning and issued severe threats on the convective outlook for days 5-6 for most of Oklahoma. The trough that is coming from the Pacific NW is I guess getting stalled by the ridge right over the plains. They are saying Monday and Tuesday will have good potential for diurunal supercells with large hail, damaging winds, and a "few" tornadoes. Once again, my work places me in the best possible spot at the best possible times.

See you all there!

At least both the GFS and the ECMWF are on board with ample moisture return in advance of this system, with both long-range models showing dewpoints </= 60 degrees reaching the I-44 corridor by early Monday. Both models are also showing CAPE values AOB 750 J/KG nudging into NC TX and WC OK by late Monday afternoon, though the 00z/03 ECMWF is a bit more generous and further north on the instability axis than the 12z/03 GFS.

The two models are starting to come into better alignment on the strengthening and track of the surface low, breaking out heavier convection across NC TX and into W/C OK after 18z Monday. SFC-500 mb bulk shear values of 60-70 kts appears to try and overspread the warm sector MON-TUE; Skew-T profiles on both the ECMWF and the GFS do appear slightly more unidirectional at this juncture, but that, of course, is subject to change as mesoscale surface details will be better defined as the event nears fruition.

 

[Andy Wade]

The last GFS forecast sounding I saw for W to C OK Monday afternoon showed most of the troposphere pretty much saturated. The lack of moisture that tends to shut down fall systems won't be an issue, but what about high clouds or showers? Normally (i.e., on a very warm spring day) it wouldn't be as much of a concern but with forecast highs only in the lower 70s, clouds and crapvection might cut surface heating too much since instability is marginal to begin with.

 

[Jeff Duda]

The more forecasts I see of the Monday/Tuesday system across the south, the less I think of them as severe weather setups. They look like good, clean, drought-denters to me. While there is a ton of moisture (in fact, PWs may be 150% - 200% of their climatological values at this time of year), the GFS, FIM, and GEM are also spitting out tons of precip that stick around all day in the threatened areas. So, even with low 60s dewpoints, low-level temps will not be much more than that, and instability is correspondingly terrible. Shear is pretty good, at least from the surface towards 850 mb, but there is some lack of speed shear above that. I really don't see this being a big severe weather event unless that mass of precip doesn't materialize, thus giving the atmosphere a chance to destabilize. There will surely be thunder embedded within, and some may even drop some large hail or gusty winds, but the storm mode looks to be linear or non-linear to me (i.e., not cellular at all).

 

[Jesse Risley]

The 12z suite of long-range models (GFS/GEM/ECMWF) are all depicting higher H7 RH values during the day on Monday for much of the region, save for the OK panhandle and points SW, and the total cloud cover graphics correspondingly depict at least some cloud cover for most of the day until the dry punch sweeps in after the surface low moves off to the northeast. Whether or not that scenario will evolve given run-to-run continuity questions remains to be seen, but it doesn't bode well for diurnal solar insolation prospects.

 

[Brett Roberts]

I haven't completely written this off yet, but I do think some people are focusing too much on OK when the real potential lies farther S. I would agree that chances for mentionable severe weather north of I-40, or even much north of the Red, are on thin ice. However, there's still a real possibility that a "wedge" of sufficient instability will develop over parts of N and W TX, between the dryline and stable/rainy air to the northeast. Since this trough is so broad, deep-layer shear should be sufficient for supercells as far S as the I-10 corridor. I'll be surprised if this is a big tornado event in classic Chase Alley, but for the desperate, chaseable supercells (tornadic or not) somewhere near the SPS-ABI-SJT corridor should be doable, depending on how things evolve over the next few days. This kind of reminds me of a typical March/April setup in TX where us Normanites are "blessed" with a long, dreary drive up and down I-35 or I-44.

 

[Brendon Lindsey]

I bet the 12z NAM put a smile on a few faces I wish I was located closer so I could chase. But from this mornings data, I would be inbetween Snyder and Hobart, OK. That Hodo is beastly for Hobart.

 

[Jesse Risley]

I bet the 12z NAM put a smile on a few faces I wish I was located closer so I could chase. But from this mornings data, I would be inbetween Snyder and Hobart, OK. That Hodo is beastly for Hobart.

There definitely is ample SRH, though it would be nice to see a bit more veering between 850 and 700 mb. However, given the more than ample shear, the 12z NAM continues to depict the incessant instability issues further north of the Red River Valley.

The forecast Skew-T Log-P diagrams from OK per this morning's 12z NAM, save for the extreme SW Red River Valley, indicate saturated columns near 850 mb for the diurnal hours, and that is also evident on a wider scope by examining the progged H85 RH values and total cloud cover graphics from the same run.

The best synchronicity between shear and instability appears to be S/WSW of the Red River Valley, essentially confined to WC Texas, though it still appears that diurnal instability might even be hampered to some extent in that region by some of the same concerns (probably higher CAPE indices being shown due to deeper moisture further south), at least per the aforesaid model depictions for that region as well.

 

[Andy Wade]

It seems safe to say, based on the 12z, 18z, and 00z NAM runs' consistency on this, that hodographs will be very, very nice around Lawton-Altus-Wichita Falls Monday afternoon. NAM is still hesitant on instability north of the Red River, and in the simulated radar product puts widespread showers in SW-SC OK much of the day. Ever since this setup first became a real prospect a couple of days ago, there's been consistent near-saturation through the depth of the troposphere on GFS forecast soundings, and as the previous poster said, the NAM is backing that up to a certain degree. I'm vaguely reminded of a rainy Friday last year (10/22/10) when a tornado watch was issued for S OK and N TX; though surface temps broke 80 down around Ardmore and points west, nothing happened except a couple short-lived weakly rotating storms near SPS. CAPE was lacking and crapvection was abundant, but impressive hodos like we're anticipating prompted higher expectations than were really warranted. The synoptic situation was likely different, I don't remember, but as far as certain parameters and seasonal timing this rings a bell. Still a game-time decision though.