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Central/Western Medium-Long Range Discussion

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Trend over the past 24 h since your post has been toward focusing the most interesting period on Monday over OK/TX, before the system becomes more barotropic thereafter. Right now it looks a bit too positive-tilt to get me excited about the hodo shape (particularly given that instability is likely to be seasonably modest), but it's nice to see the above-average November severe activity continue.

 

http://www.pivotalweather.com/model.php?m=GFS&p=03ehi&rh=2015111212&fh=108&r=sc&lat=33.5000&lon=-98.3780&metar=

 

ECMWF looks relatively similar this afternoon, with 1000 J/kg SBCAPE nosing into SW OK by Monday afternoon.

The focus has shifted earlier, but perhaps not enough for a big day on Monday. Although the evening looks interesting, the best environment seems to occur overnight across eastern Texas. It's the 06z-12z time-frame that instability is maximized, as the low-level jet really cranks and mid-level lapse rates steepen. 

 

Speed this up a bit and it could be really interesting. Tuesday looks messy, although I could see a potent squall line early in the day with embedded tornadoes.

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Debating on a post...keep in mind...the first graphics are for the last on the WPC.

 

OPC 500mb North Pacific...note the split flow in the Sea of Okhotsk?

 

November 20th

 

00z

v0ysq0E.gif

 

12Z

BjkusbO.gif

 

November 21st

 

00z

XH79vNc.gif

 

12z

yuaSDxw.gif

 

 

WPC 500mb Day 3-7 forecast

q75Q1Ov.gif

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Continued...

 

November 22nd

 

00z

8H2e0yL.gif

 

12z

TYWxfux.gif

 

Finally...November 23rd

 

00z

q0bm0bP.gif

 

12z

oycWC3O.gif

 

 

WPC 500mb Day 3-7 forecast

q75Q1Ov.gif

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Continued strong signal from the EPS and GEFS for a large western trough developing later next week, thanks to a very impressive jet over the Pacific and a lack of a blocking ridge along the W Coast. Favorable teleconnections with troughing in the Gulf of Alaska (+EPO and -PNA) look to be in place to get this moving into the CONUS.

 

Wouldn't be surprised if 2015 has at least one last go of it in the severe department should this end up verifying, especially considering the location of the SE ridge axis out ahead and what may be quite a moist warm sector (especially by December's standards) by the time the upper level jet pushes eastward of the Rockies. Deep moisture trajectories on the Euro look pretty prototypical for what you would want to see in a cold season event, coming right through the Caribbean. Then it comes down to what character the trough ejection assumes, and whether it will be sheared out if the ridge amplifies too much ahead of it, or whether it amplifies too much and becomes too meridional.

 

This is of course barring any complications from the active southern stream, i.e. shortwaves disrupting the return flow. The more reliable Euro has not been showing this to the extent that the NA models have though, thus has more instability. Regardless, as usual this time of year, the biggest question is always moisture quality and from what I'm seeing, this system does have a reasonably good chance of achieving that. With a very potent jet like this moving onto the W Coast, that is definitely an eyebrow raiser.

 

ecmwf-ens_z500a_namer_9.png

gfs-ens_z500a_namer_33.png

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12z Euro has another seasonally impressive event. As usual, GFS is more modest... but that's to be expected.

j1Vd8WN.png

uYXPSMV.png

GFS is leaning heavily on climo which makes sense at this range, the fact it shows any instability is a good sign.

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Then it comes down to what character the trough ejection assumes, and whether it will be sheared out if the ridge amplifies too much ahead of it, or whether it amplifies too much and becomes too meridional.

 

This looks to be what most recent guidance has suggested.

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After a potential outbreak on the fringes of this subforum tomorrow, Sunday could bring another severe event. At the very least, have to expect some potentially heavy snow across portions of the southern High Plains into central Plains.

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My research suggests that it is very rare for snowy Decembers in the SW to continue into snowy Januaries - we may get a bunch of little storms, but I think we're kind of due for a quiet period around maybe Jan 20 - Feb 20 before the action resumes with impressively strong/cold storms plowing way south in the West again until maybe May 20. My idea for this winter has always been cold/wet in the NW in the fall, that cold/wet area moves south and east in Dec and early January. The east bakes until late January, then they have one month of winter. After the east has it's one month of winter we get two-three months of cold (often snowy, but not always) spring storms. Could still be completely wrong, but we'll have to see.

 

Main differences from last year are the warmer AMO and cooler PDO, and the El Nino will likely be weakening, not strengthening in the Spring.

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Far West Texas, and New Mexico are in for rapidly changing conditions characterized by warm weather transitioning to very cold with heavy snow and blizzard conditions. Farther east in Austin, a generally fast moving squall will form and blast through the I 35 Corridor in a rather short time followed by breezy and colder.

 

Heavier rain will be found in the usual regions: Coastal sections, Houston, East Texas, Louisiana, and Oklahoma, where snow will develop as well, This is going to be memorable everywhere in the southwest US except for Austin lol, unless you like high winds and tornadoes. I'm crazy, but I am not one of those fkin crazy nuts that likes tornadoes.

 

To sum up: I'm damn glad I'll be getting the hell out of this southwestern climate in a few short days.

I prefer cloudy rainy weather and flooding.

 

The farther east and north from Austin one travels, the more steady and heavy rain one shall find. In the more northern areas, rain will change to snow and pile up and blow around. The northern guys can have the snow. I enjoy rain and lots of it.

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Far West Texas, and New Mexico are in for rapidly changing conditions characterized by warm weather transitioning to very cold with heavy snow and blizzard conditions. Farther east in Austin, a generally fast moving squall will form and blast through the I 35 Corridor in a rather short time followed by breezy and colder.

 

Heavier rain will be found in the usual regions: Coastal sections, Houston, East Texas, Louisiana, and Oklahoma, where snow will develop as well, This is going to be memorable everywhere in the southwest US except for Austin lol, unless you like high winds and tornadoes. I'm crazy, but I am not one of those fkin crazy nuts that likes tornadoes.

 

To sum up: I'm damn glad I'll be getting the hell out of this southwestern climate in a few short days.

I prefer cloudy rainy weather and flooding.

 

The farther east and north from Austin one travels, the more steady and heavy rain one shall find. In the more northern areas, rain will change to snow and pile up and blow around. The northern guys can have the snow. I enjoy rain and lots of it.

Jebman why were/are  you away from the lovely mid atlantic??? 

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To sum up: I'm damn glad I'll be getting the hell out of this southwestern climate in a few short days.

I prefer cloudy rainy weather and flooding.

The farther east and north from Austin one travels, the more steady and heavy rain one shall find. In the more northern areas, rain will change to snow and pile up and blow around. The northern guys can have the snow. I enjoy rain and lots of it.

I'd let you borrow part of the 11+ inches of rain I got from this monster. Lol. Set some all time records for several locations for river floods of record in NE OK. That's saying a lot considering most were set in our more rainy seasons of spring or fall. Been a crazy couple of days.

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Both the EPS and the GEFS are signaling a major long-range pattern shift toward the the end of January and the first week of February (especially around 28 Jan–1 Feb), with a restrengthening of the polar vortex and at least a transient +NAO/–EPO/–PNA period taking hold. Even at this range, models are indicating that the polar jet will take over as the dominant stream with strong hints of multiple shortwave impulses intruding into the Pacific Northwest, likely inducing lee cyclogenesis east of the Rockies. Details regarding ejection and overall evolution are obviously too early to ascertain, but the overall trend toward a more zonal look/longer wavelengths favors a Southeast ridge with likely favorable moisture vectors out of the Caribbean, setting up a potentially decent return flow over the southern High Plains for a few days in advance of any potential ejecting disturbance. There aren't many analogs from strong El Niño events since 1950, but an interesting one is 26 Feb 1958, which was somewhat similar synoptic-wise and featured several significant tornadoes across LA and MS. An interesting difference is that this case may also extend the opportunity for severe weather to the southern High Plains.

 

NMgEulw.gif

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Models continue to advertise a potentially significant threat around 30 Jan–1 Feb, with the 12Z deterministic ECMWF and the 12Z EPS showing one of the warmest low-level air masses since 26 Dec 2015 (the date of the Garland, TX, EF4 tornado) over the southern High Plains for multiple days. In fact, even the EPS mean shows 15°C 850-mb temperatures reaching as far north as the TX/OK panhandles on at least two of the days that I mentioned. One important key is the relatively low amplitude of the upcoming pattern, with its lack of significant cold intrusions, which not only may prevent heights from rising too much ahead of any ejecting disturbance, but also allows southwesterly low-level flow to advect richer instability (as well as a noticeable if not strong elevated mixed layer, which is surprising given the subtropical jet) north from the Mexican plateau. The tongue of greatest instability is likely to be at least a bit narrower than projected at this point, but the fact that we are talking about EMLs and a potentially significant southern High Plains threat in a potent El Niño says a lot.

 

For reference:

 

0KsFC23.gif

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Not really seeing the significant threat part of this right now. Lack of thermodynamics and a cold air intrusion into the Gulf in the days leading up to this system could put a lid on this one. Could still be good for a marginal low CAPE/high shear setup, but I'm not sold on this being a significant threat unless thermodynamic profiles start trending upward. 

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Models continue to advertise a potentially significant threat around 30 Jan–1 Feb, with the 12Z deterministic ECMWF and the 12Z EPS showing one of the warmest low-level air masses since 26 Dec 2015 (the date of the Garland, TX, EF4 tornado) over the southern High Plains for multiple days. In fact, even the EPS mean shows 15°C 850-mb temperatures reaching as far north as the TX/OK panhandles on at least two of the days that I mentioned. One important key is the relatively low amplitude of the upcoming pattern, with its lack of significant cold intrusions, which not only may prevent heights from rising too much ahead of any ejecting disturbance, but also allows southwesterly low-level flow to advect richer instability (as well as a noticeable if not strong elevated mixed layer, which is surprising given the subtropical jet) north from the Mexican plateau. The tongue of greatest instability is likely to be at least a bit narrower than projected at this point, but the fact that we are talking about EMLs and a potentially significant southern High Plains threat in a potent El Niño says a lot.

 

For reference:

 

0KsFC23.gif

 

Apply our findings that the BSR is ~378 miles SE of the OBS 19-20 days in advance, I'd venture the severe weather threat is decent. ;)

 

160118011300.jpg

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Looks like today's 12Z GFS and ECMWF runs highlight two different return flow scenarios. This run of the ECMWF looks considerably more robust with its modeled warm sector when compared to this particular GFS run. The 570 dam thickness of the former lies across Texas while the latter depicts it still well offshore in the Gulf. Lots of variability still.

a389a39a2713faadc8ee8d1943421552.jpg

48007af87e7181f161d44c8e24a66199.jpg

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Two approaches with analogs...

 

The GEFS long-range suite for 00/03 shows some severe risk across Dixie. When using the CPC d6-10 analogs and overlaying the events within 48 hours of the target, there are a few clusters over the Gulf Coast states:

post-533-0-16089200-1453674532_thumb.png

post-533-0-18973600-1453674541_thumb.jpg

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It looks like the GFS has some disturbance in the STJ that limits moisture return. Either way it's very difficult to tell this far out. The ejecting trough has been looking impressive for a few runs now.

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Something is going to happen, but will it be significant and what area will be targeted? Climo seems to favor Gulf Coast/Dixie, but even with poor instability, this sort of setup would probably still produce at least some severe. It's been a very consistent signal, overall, on the models for quite some time:

post-533-0-50617200-1453771327_thumb.jpg

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This is a bit preliminary since we're not through February yet, but I grabbed the six driest Marches in an El Nino for Albuquerque and compared them to the last 90 days of precipitation anomalies. NW and MW look completely different, which makes me think the wet March idea is real? Not expecting huge totals, but above normal looks likely.

 

http://www.cpc.ncep.noaa.gov/products/Precip_Monitoring/Figures/NAMS/p.90day.figb.gif

 

p.90day.figb.gif

cd67.0.147.247.47.14.56.26.prcp.png

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Long-range ensembles have begun to pick up on a pretty progressive central/eastern ridging and western troughing pattern towards the end of the run, with some good consistency between all 3 ensembles. Has that trough swinging into the southwest at the end of the run and ejecting out over the plains. CFS seems to have keyed in on this system as well, and seems to be favoring TX/OK and eastward into Dixie for a shot at possibly some severe weather within the 9th-12th timeframe. 

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Medium range guidance is optimistic about shifting to a mean western trough around next weekend into the following week. That should at the very least mean rain chances on the Plains and a lack of Gulf-wiping fronts, if not some severe weather opportunities.

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